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Improper repair of battery operated devices can also result in bad consequences for you, the device, and any equipment attached to it.
We will not be responsible for damage to equipment, your ego, county wide power outages, spontaneously generated mini (or larger) black holes, planetary disruptions, or personal injury or worse that may result from the use of this material.
However, if you can do the repair yourself, the equation changes dramatically as your parts costs will be 1/2 to 1/4 of what a professional will charge and of course your time is free. The educational aspects may also be appealing. You will learn a lot in the process. Many problems can be solved quickly and inexpensively. Fixing an old vacuum cleaner to keep in the rec room may just make sense after all.
This document provides maintenance and repair information for a large number of small household appliances and portable power tools. The repair of consumer electronic equipment is dealt with by other documents in the "Notes on the Troubleshooting and Repair of..." series. Suggestions for additions (and, of course, correction) are always welcome.
You will be able to diagnose problems and in most cases, correct them as well. Most problems with household appliances are either mechanical (e.g., dirt, lack of or gummed up lubrication, deteriorated rubber parts, broken doohickies) or obvious electrical (e.g., broken or corroded connections, short circuits, faulty heating elements) in nature. With minor exceptions, specific manufacturers and models will not be covered as there are so many variations that such a treatment would require a huge and very detailed text. Rather, the most common problems will be addressed and enough basic principles of operation will be provided to enable you to narrow the problem down and likely determine a course of action for repair. In many cases, you will be able to do what is required for a fraction of the cost that would be charged by a repair center - or - be able to revive something that would otherwise have gone into the dumpster - or remained in that closet until you moved out of your house (or longer)!
Since so many appliances are variations on a theme - heating, blowing, sucking, rotating, etc. - it is likely that even if your exact device does not have a section here, a very similar one does. Furthermore, with your understanding of the basic principles of operation, you should be able to identify what is common and utilize info in other sections to complete a repair.
Should you still not be able to find a solution, you will have learned a great deal and be able to ask appropriate questions and supply relevant information if you decide to post to sci.electronics.repair (recommended), alt.home.repair, or misc.consumers.house. It will also be easier to do further research using a repair textbook. In any case, you will have the satisfaction of knowing you did as much as you could before finally giving up or (if it is worthwhile cost-wise) taking it in for professional repair. With your newly gathered knowledge, you will have the upper hand and will not easily be snowed by a dishonest or incompetent technician.
Thus, in the end, these device increase costs if you need to use more or larger bulbs to make up for the reduced light output. The major life cycle expense for incandescent lighting is not the cost of the bulbs but the cost of the electricity - by a factor of 25 to 50! For example, it costs about $10 in electricity to run a 100 W bulb costing 25 cents over the course of its 1000 hour life. However, these devices (or the use of 130 V bulbs) may make sense for use in hard-to-reach locations. Better yet, consider compact or normal fluorescent bulbs or fixtures which last much longer and are much more efficient than incandescents (including halogen).
The Green Plug is supposed to reduce reactive power (V and I out of phase due to inductive or capacitive loads) but residential users don't pay for reactive power anyway, only the real power they use. In addition, this is a minor concern for modern appliances.
The demo you see in the store that shows a utility meter slowing down substantially when the Green Plug is put in the circuit is bogus for two reasons: (1) The motor being powered is totally unloaded resulting in a high ratio of reactive to real power. Under normal use with a motor driving a load, the reduction in electricity use would be negligible. (2) The meter is wired to include reactive power in its measurement which, as noted above, is not the case with residential customers.
Mention the word 'magnetism' and somehow, people will pay $300 for $2 worth of magnets that do nothing - and then be utterly convinced of their effectiveness. They forget that perhaps the instruction manual suggested changes in their water use habits - which was the true reason for any improvement. Perhaps the magnets can be used to stick papers on the refrigerator once you discover they don't do anything for the water.
BTW, the same goes for magnetic wine flavor enhancers. :-)
I will be happy to revise these comments if someone can provide the results of evaluations of any of these devices conducted by a recognized independent testing laboratory. However, I won't hold my breath waiting.
The easiest way to explain basic electrical theory without serious math is with a hydraulic analogy. This is of the plumbing system in your house:
Water is supplied by a pipe in the street from the municipal water company or by a ground water pump. The water has a certain pressure trying to push it through your pipes. With electric circuits, voltage is the analog to pressure. Current is analogous to flow rate. Resistance is analogous the difficulty in overcoming narrow or obstructed pipes or partially open valves.
Intuitively, then, the higher the voltage (pressure), the higher the current (flow rate). Increase the resistance (partially close a valve or use a narrower pipe) and for a fixed voltage (constant pressure), the current (flow rate) will decrease.
With electricity, this relationship is what is known as linear: double the voltage and all other factors remaining unchanged, the current will double as well. Increase it by a factor of 3 and the current will triple. Halve the resistance and for a constant voltage source, the current will double. (For you who are hydraulic engineers, this is not quite true with plumbing as turbulent flow sets in, but this is just an analogy, so bear with me.)
Note: for the following 4 items whether the source is Direct Current (DC) such as a battery or Alternating Current (AC) from a wall outlet does not matter. The differences between DC and AC will be explained later.
The simplest electrical circuit will consist of several electrical components in series - the current must flow through all of them to flow through any of them. Think of a string of Christmas lights - if one burns out, they all go out because the electricity cannot pass through the broken filament in the burned out bulb.
Note the term 'circuit'. A circuit is a complete loop. In order for electricity to flow, a complete circuit is needed.
Switch (3)
_____________/ ______________
| |
| (1) | (4)
+-------+--------+ +---+----+
| Power Source | | Load |
+-------+--------+ +---+----+
| Wiring (2) |
|_____________________________|
With household water we usually don't think of the load. However, things like lawn sprinklers, dishwasher rotating arms, pool sweepers, and the like do convert water flow to mechanical work in the home (some homes, at least!). Hydraulic motors are used to aircraft and spacecraft, large industrial robots, and all sorts of other applications.
Here are 3 of the simplest appliances:
Now we can add one type of simple control device:
With the addition of a thermostat, many more appliances can be constructed including (this is a small subset):
Electric heaters and cooking appliances usually have adjustable thermostats.
Hair dryers may simply have several settings which adjust heater power and fan speed (we will get into how later). The thermostat may be fixed and to protect against excessive temperatures only.
That's it! You now understand the basic operating principle of nearly all small appliances. Most are simply variations (though some may be quite complex) on these basic themes. Everything else is just details.
For example, a blender with 38 speeds just has a set of buttons (switches) to select various combinations of motor windings and other parts to give you complete control (as if you need 38 speeds!). Toasters have a timer or thermostat activate a solenoid (electromagnet) to pop your bread at (hopefully) the right time.
A significant amount of the power the electric company produces is lost to heating of the transmission lines due to resistance and heating.
However, in an electric heater, this is put to good use. In a flashlight or table lamp, the resistance inside the light bulb gets so hot that it provides a useful amount of light.
A bad connection or overloaded extension cord, on the other hand, may become excessively hot and start a fire.
The following is more advanced - save for later if you like.
Capacitors are not that common in small appliances but may be used with some types of motors and in RFI - Radio Frequency Interference - filters as capacitors can buffer - bypass - interference to ground. The energy to power an electronic flash unit is stored in a capacitor, for example. Because they act like reservoirs - buffers - capacitors are found in the power supplies of most electronic equipment to smooth out the various DC voltages required for each device.
The windings of motors and transformers have significant inductance but the use of additional inductance devices is rare in home appliances except for RFI - since inductance tends to prevent current from changing, it can also be used to prevent interference from getting in or out.
The simplest of these are:
V = I * R (1)
I = V / R (2)
R = V / I (3)
Where:
P = V * I (4)
P = V * V / R (5)
P = I * I * R (6)
For example:
A direct current source is at a constant voltage. Displaying the voltage versus time plot for such a source would show a flat line at a constant level. Some examples:
The nominal voltage from an AC outlet in the U.S. is around 115 VAC. This is the RMS (Root Mean Square) value, not the peak (0 to maximum). In simple terms, the RMS value of an AC voltage and the same value of a DC voltage will result in identical heating (power) to a resistive load. For example, 115 VAC RMS will result in the same heat output of a broiler as 115 VDC.
Direct current is used for many small motor driven appliances particularly when battery power is an option since changing DC into AC requires some additional circuitry. All electronic equipment require various DC voltages for their operation. Even when plugged into an AC outlet, the first thing that is done internally (or in the AC adapter in many cases) is to convert the AC to various DC voltages.
The beauty of AC is that a very simple device - a transformer - can convert one voltage into another. This is essential to long distance power distribution where a high voltage and low current is desirable to minimize power loss (since it depends on the current). You can see transformers atop the power poles in your neighborhood reducing the 2,000 VAC or so from a local distribution transformer to your 115 VAC (actually, 115-0-115 were the total will be used by large appliances like electric ranges and clothes dryers). That 2,000 VAC was stepped down by a larger transformer from around 12,000 VAC provided by the local substation. This, in turn, was stepped down from the 230,000 VAC or more used for long distance electricity transmission. Some long distance lines are over 1,000,000 volts (MV).
When converting between one voltage and another with a transformer, the amount of current (amps) changes in the inverse ratio. So, using 230 kV for long distance power transmission results in far fewer heating losses as the current flow is reduced by a factor of 2,000 over what it would be if the voltage was only 115 V, for example. Recall that power loss from P=I*I*R is proportional to the square of the current and thus in this example is reduced by a factor of 4,000,000!
Many small appliances include power transformers to reduce the 115 VAC to various lower voltages used by motors or or electrical components. Common AC adapters - often simply called transformers or wall warts - include a small transformer as well. Where their output is AC, this is the only internal component other than a fuse or thermal fuse for protection. Where their output is DC, additional components convert the low voltage AC from the transformer to DC and a capacitor smoothes it out.
The loads, say resistance heating elements, are now drawn with the schematic symbol (as best as can be done using ASCII) for a resistor.
Switch
_____________/ __________________
| I --> |
| ^ ^ |
| | | / R1
| | V1 \ Load 1
+-------+--------+ | | /
| Power Source | v__ |
+-------+--------+ V(S) ^ |
| | / R2
| | V2 \ Load 2
| | | /
| v v |
|_________________________________|
The total resistance, R(T), of the resistors in this series circuit is:
R(T) = R1 + R2 (7)
The voltage across each of the resistors would be given by:
V1 = V(S) * R1 / (R1 + R2) (8)
V2 = V(S) * R2 / (R1 + R2) (9)
The current is given by:
I = V(S) / (R1 + R2) (10)
However, another basic configuration, is also possible. With a parallel
circuit, components are connected not one after the other but next to
one another as shown below:
Switch
_____________/ ___________________________
| I --> | |
| ^ | |
+-------+--------+ | / R1 / R2
| Power Source | V(S) \ Load 1 \ Load 2
+-------+--------+ | / /
| v |v I(1) |v I(2)
|_____________________________|____________|
Now, the voltages across each of the loads is necessarily equal but the
individual currents divide according to the relative resistances of each
load.
The total resistance, R(T), of the parallel resistors in this circuit is:
R(T) = (R1 * R2) / (R1 + R2) (11)
The currents through each of the loads would be given by:
I1 = V(S)/R1 (12)
I2 = V(S)/R2 (13)
The total current is given by:
I = I1 + I2 (14)
Many variations on these basic arrangements are possible but nearly all can
be reduced systematically to a combination of series or parallel circuits.
Check out Sam's Neat, Nifty, and Handy Bookmarks in the "Education and Tutorials" area for links to introductory material on electronics and other related fields.
However, AC line power can be lethal. Proper safety procedures must be followed whenever working on live equipment (as well as devices which may have high energy storage capacitors like TVs, monitors, and microwave ovens). AC line power due to its potentially very high current is actually considerably more dangerous than the 30 kV found in a large screen color TV!
These guidelines are to protect you from potentially deadly electrical shock hazards as well as the equipment from accidental damage.
Note that the danger to you is not only in your body providing a conducting path, particularly through your heart. Any involuntary muscle contractions caused by a shock, while perhaps harmless in themselves, may cause collateral damage - there are many sharp edges inside this type of equipment as well as other electrically live parts you may contact accidentally.
You may have heard warnings about dangers from unplugged appliances. Perhaps, these were passed down from your great great grandparents or from local bar room conversation.
Except for devices with large high voltage capacitors connected to the line or elsewhere, there is nothing inside an appliance to store a painful or dangerous charge. Even these situations are only present in microwave ovens, fluorescent lamps and fixtures with electronic ballasts, universal power packs for camcorders or portable computers, or appliances with large motors. Other than these, once an appliance is unplugged all parts are safe to touch - electrically that is. There may still be elements or metal brackets that are burning hot as metal will tend to retain heat for quite a while in appliances like toasters or waffle irons. Just give them time to cool. There are often many sharp edges on sheetmetal as well. Take your time and look before you leap or grab anything.
The use of a GFCI (Ground Fault Circuit Interrupter) protected outlet is a good idea but will not protect you from shock from many points in a line connected TV or monitor, or the high voltage side of a microwave oven, for example. (Note however, that, a GFCI may nuisance trip at power-on or at other random times due to leakage paths (like your scope probe ground) or the highly capacitive or inductive input characteristics of line powered equipment.) A fuse or circuit breaker is too slow and insensitive to provide any protection for you or in many cases, your equipment. However, these devices may save your scope probe ground wire should you accidentally connect it to a live chassis.
BTW, electronic equipment should always be unplugged during lightning storms since it may be very susceptible to power surge and lightning damage. Don't forget the telephones and computer modems as well. This is not as much of a problem with small appliances that do not include electronic controllers as except for direct lightning strikes, the power switch will provide protection.
If you get stuck, sleep on it. Sometimes, just letting the problem bounce around in your head will lead to a different more successful approach or solution. Don't work when you are really tired - it is both dangerous and mostly non-productive (or possibly destructive - especially with AC line powered appliances).
Whenever working on precision equipment, make copious notes and diagrams. Yes, I know, a toaster may not exactly be precision equipment, but trust me. You will be eternally grateful when the time comes to reassemble the unit. Most connectors are keyed against incorrect insertion or interchange of cables, but not always. Apparently identical screws may be of differing lengths or have slightly different thread types. Little parts may fit in more than one place or orientation. Etc. Etc.
Pill bottles, film canisters, and plastic ice cube trays come in handy for sorting and storing screws and other small parts after disassembly.
Select a work area which is well lighted and where dropped parts can be located - not on a deep pile shag rug. Something like a large plastic tray with a slight lip may come in handy as it prevents small parts from rolling off of the work table. The best location will also be relatively dust free and allow you to suspend your troubleshooting to eat or sleep or think without having to pile everything into a cardboard box to eat dinner.
An electric drill or drill press with a set of small (1/16" to 1/4") high quality high speed drill bits is handy for some types of restoration where new holes need to be provided. A set of machine screw taps is also useful at times.
A medium power soldering iron and rosin core solder (never never use acid core solder or the stuff for sweating copper pipes on electrical or electronic repairs!) will be required if you need to make or replace any soldered connections. A soldering gun is desirable for any really beefy soldering. See the section: Soldering techniques.
A crimping tool and an assortment of solderless connectors often called 'lugs' will be needed to replace damaged or melted terminals in small appliances. See the section: Solderless connectors.
Old dead appliances can often be valuable sources of hardware and sometimes even components like switches and heating elements. While not advocating being a pack rat, this does have its advantages at times.
Use of the proper technique is critical to reliability and safety. A good solder connection is not just a bunch of wires and terminals with solder dribbled over them. When done correctly, the solder actually bonds to the surface of the metal (usually copper) parts.
CAUTION: You can easily turn a simple repair (e.g., bad solder connections) into an expensive mess if you use inappropriate soldering equipment and/or lack the soldering skills to go along with it. If in doubt, find someone else to do the soldering or at least practice, practice, practice, soldering and desoldering on a junk unit first!
Effective soldering is by no means difficult but some practice may be needed to perfect your technique.
The following guidelines will assure reliable solder joints:
See the document: Troubleshooting and Repair of Consumer Electronic Equipment for additional info on desoldering of electronic components.
One approach that works in some cases is to use the mating socket to stabilize the pins so they remain in position as you solder. The plastic will still melt - not as much if you use an adequately sized iron since the socket will act as a heat sink - but will not move.
An important consideration is using the proper soldering iron. In some cases, a larger iron is better - you get in and out more quickly without heating up everything in the neighborhood.
WireNuts allow multiple wires to be joined by stripping the ends and then 'screwing' an insulated thimble shaped plastic nut onto the grouped ends of the wires. A coiled spring (usually) inside tightly grips the bare wires and results in a mechanically and electrically secure joint. For appliance repair, the required WireNuts will almost always already be present since they can usually be reused. If you need to purchase any, they come in various sizes depending on the number and size of the wires that can be handled. It is best to twist the individual conductor strands of each wire together and then twist the wires together slightly before applying the WireNut.
Crimped connectors, called lugs, are very common in small appliances. One reason is that it is easier, faster, and more reliable, to make connections using these lugs with the proper crimping equipment than with solder.
A lug consists of a metal sleeve which gets crimped over one or more wires, an insulating sleeve (usually, not all lugs have these), and a terminal connection: ring, spade, or push-on are typical.
Lugs connect one or more wires to the fixed terminals found on switches, motors, thermostats, and so forth.
There are several varieties:
In the factory, the lugs are installed on the wires with fancy expensive equipment. For replacements, an inexpensive crimping tool and an assortment of lugs will suffice. The crimping tool looks like a pair of long pliers and usually combines a wire stripper and bolt cutter with the crimping function. It should cost about $6-10.
The crimping tool 'squashes' the metal sleeve around the stripped ends of the wires to be joined. A proper crimp will not come apart if an attempt is made to pull the wires free - the wires will break somewhere else first. It is gas-tight - corrosion (within reason) will not affect the connection.
Crimping guidelines:
A pen knife or Xacto knife can be used in a pinch but a wire stripper is really much much easier.
First, start with some analytical thinking. Many problems associated with household appliances do not require a schematic. Since the internal wiring of many appliances is so simple, you will be able to create your own by tracing the circuits in any case. However, for more complex appliances, a schematic may be useful as wires may run behind and under other parts and the operation of some custom switches may not obvious. The causes for the majority of problems will be self evident once you gain access to the interior - loose connections or broken wires, bad switches, open heating element, worn motor brushes, dry bearings. All you will need are some basic hand tools, a circuit and continuity tester, light oil and grease, and your powers of observation (and a little experience). Your built in senses and that stuff between your ears represents the most important test equipment you have.
The following will be highly desirable for all but the most obvious problems:
These are just a set of 3 neon bulbs+resistors across each pair of wires. If the correct bulbs light at full brightness - H-N, H-G - then the circuit is likely wired correctly. If the H-G light is dim or out or if both the H-G and G-N are dim, then you have no ground. If the N-G light is on and the H-G light is off, you have reversed H and N, etc.
What it won't catch: Reversed N and G (unlikely unless someone really screwed up) and marginal connections since the neon bulbs doesn't use much current. For this (particularly important for the G since it won't do any good if its resistance back to the service panel is too high) you need a real load like a 100 W light bulb. Or, build a tester consisting of 100 W light bulbs (instead of neon lamps) wired between each of the prongs.
It also won't distinguish between 110 VAC and 220 VAC circuits except that the neon bulbs will glow much brighter on 220 VAC but without a direct comparison, this could be missed.
For something that appears to test for everything but next week's weather:
(From: Bill Harnell (bharne@adss.on.ca).)
Get an ECOS 7105 tester! (ECOS Electronics Corporation, Oak Park, Illinois, 708-383-2505). Not cheap, however. It sold for $59.95 in 1985 when I purchased somewhere around 600 of them for use by our Customer Engineers for safety purposes!
It tests for:
Correct wiring, reversed polarity, open Ground, open Neutral, open Hot, Hot & Ground reversed, Hot on neutral, Hot unwired, other errors, over voltage (130 VAC+), under voltage (105 VAC-), Neutral to Ground short, Neutral to Ground reversal, Ground impedance test (2 Ohms or less ground impedance - in the equipment ground conductor).
Their less expensive 7106 tester performs almost all of the above tests.
FWIW, I have no interest in the ECOS Corporation of any kind. Am just a very happy customer.
A continuity tester can be constructed very easily from an Alkaline battery, light bulb or buzzer, some wire, and a set of test leads with probes. All of these parts are available at Radio Shack.
AA, C, or D cell 1.5 V flashlight bulb or buzzer
+| - +------------------+
Test probe 1 o-----------| |--------------| Bulb or buzzer |-------+
| +------------------+ |
|
Test probe 2 o-------------------------------------------------------+
CAUTION: Do not use this simple continuity tester on electronic equipment as there is a slight possibility that the current provided by the battery will be too high and cause damage. It is fine for most appliances.
Wire a 3 prong plug with a 15 K ohm 1 W resistor between H and G. Insulate and label it! This should trip a GFCI protected outlet as soon as it is plugged in since it will produce a fault current of about 7 mA.
Note that this device will only work if there is an actual Safety Ground connection to the outlet being tested. A GFCI retrofitted into a 2 wire installation without a Ground cannot be tested in this way since a GFCI does not create a Ground. However, jumpering this rig between the H and and a suitable earth ground (e.g., a cold water in an all copper plumbing system) should trip the GFCI. Therefore, first use an Outlet Tester (above) to confirm that there is a Safety Ground present.
The test button works because it passes an additional current through the sense coil between Hot and Neutral tapped off the wiring at the line side of the GFCI and therefore doesn't depend on having a Ground.
If you want to be fancier, you can build a combination outlet and GFCI tester. Wire up a neon indicator with current limiting resistor) across each pair of wires. Add a 15K ohm 1 W resistor in series with a pushbutton switch between H and G. If the H-G neon is lit (indicating a proper Ground connection), pressing the button should trip the GFCI.
Note: For testing of household electrical wiring, a VOM or DMM can indicate voltage between wires which is actually of no consequence. This is due to the very high input resistance/impedance of the instrument. The voltage would read zero with any sort of load. See the section: Phantom voltage measurements of electrical wiring.
Appliance manufacturers seem to take great pride in being very mysterious as to how to open their equipment. Not always, but this is too common to just be a coincidence.
A variety of techniques are used to secure the covers on consumer electronic equipment:
These are almost always of the Philips variety though more and more appliances are using Torx or security Torx type screws. Many of these are hybrid types - a slotted screwdriver may also work but the Philips or Torx is a whole lot more convenient.
A precision jeweler's screwdriver set including miniature Philips head drivers is a must for repair of miniature portable devices.
When reinstalling the screws, first turn them in a counter-clockwise direction with very slight pressure. You will feel them "click" as they fall into the already formed threads. Gently turn clockwise and see if they turn easily. If they do not, you haven't hit the previously formed threads - try again. Then just run them in as you normally would. You can always tell when you have them into the formed threads because they turn very easily for nearly the entire depth. Otherwise, you will create new threads which will quickly chew up the soft plastic. Note: these are often high pitch screws - one turn is more than one thread - and the threads are not all equal.
The most annoying (to be polite) situation is when after removing the 18 screws holding the case together (losing 3 of them entirely and mangling the heads on 2 others), removing three subassemblies, and two other circuit boards, you find that the adjustment you wanted was accessible through a hole in the case just by partially peeling back a rubber hand grip! (It has happened to me).
When reassembling the equipment make sure to route cables and other wiring such that they will not get pinched or snagged and possibly broken or have their insulation nicked or pierced and that they will not get caught in moving parts. This is particularly critical for AC line operated appliances and those with motors to minimize fire and shock hazard and future damage to the device itself. Replace any cable ties that were cut or removed during disassembly and add additional ones of your own if needed. Some electrical tape may sometimes come in handy to provide insulation insurance as well. As long as it does not get in the way, additional layers of tape will not hurt and can provide some added insurance against future problems. I often put a layer of electrical tape around connections joined with WireNuts(tm) as well just to be sure that they will not come off or that any exposed wire will not short to anything.
Appliances containing fans or blowers seem to be dust magnets - an incredible amount of disgusting fluffy stuff can build up in a short time - even with built-in filters.
Use a soft brush (like a new cheap paint brush) to remove as much dirt, dust, and crud, as possible without disturbing anything excessively. Some gentle blowing (but no high pressure air) may be helpful in dislodged hard to get at dirt - but wear a dust mask.
Don't use compressed air on intricate mechanisms, however, as it might dislodge dirt and dust which may then settle on lubricated parts and contaminating them. High pressure air could move oil or grease from where it is to where it should not be. If you are talking about a shop air line, the pressure may be much much too high and there may be contaminants as well.
A Q-tip (cotton swab) moistened with politically correct alcohol can be used to remove dust and dirt from various hard to get at surfaces.
NEVER, ever, use WD40! WD40 is not a good lubricant despite the claims on the label. Legend has it that the WD stands for Water Displacer - which is one of the functions of WD40 when used to coat tools for rust prevention. WD40 is much too thin to do any good as a general lubricant and will quickly collect dirt and dry up. It is also quite flammable and a pretty good solvent - there is no telling what will be affected by this.
A light machine oil like electric motor or sewing machine oil should be used for gear or wheel shafts. A plastic safe grease like silicone grease or Molylube is suitable for gears, cams, or mechanical (piano key) type mode selectors. Never use oil or grease on electrical contacts.
One should also NOT use a detergent oil. This includes most automotive engine oils which also have multiple additives which are not needed and are undesirable for non-internal combustion engine applications.
3-In-One(tm) isn't too bad if that is all you have on hand and the future of the universe depends on your fan running smoothly. However, for things that don't get a lot of use, it may gum up over time. I don't know whether it actually decomposes or just the lighter fractions (of the 3) evaporate.
Unless the unit was not properly lubricated at the factory (which is quite possible), don't add any unless your inspection reveals the specific need. Sometimes you will find a dry bearing, motor, lever, or gear shaft. If possible, disassemble and clean out the old lubricant before adding fresh oil or grease.
Note that in most cases, oil is for plain bearings (not ball or roller) and pivots while grease is used on sliding parts and gear teeth.
In general, do not lubricate anything unless you know there is a need. Never 'shotgun' a problem by lubricating everything in sight! You might as well literally use a shotgun on the equipment!
Testing: If the problem is intermittent, (or even if it is not), plug the appliance in and turn it on. Then try bending or pushing the wire toward the plug or appliance connector end to see if you can make the internal conductors touch at least momentarily. Ii the cordset is removable, test between ends with a continuity checker or multimeter on the low ohms scale. If it is not detachable, open the appliance to perform this test.
Testing: In many cases, a visual inspection with some careful flexing and prodding will reveal the location of the bad connection. If it is an intermittent, this may need to be done with a well insulated stick while the appliance is on and running (or attempting to run). When all else fails, the use of a continuity checker or multimeter on the low ohms scale can identify broken connections which are not obviously wires visibly broken in two. For testing heating elements, use the multimeter as a continuity checker may not be sensitive enough since the element normally has some resistance.
A short circuit may develop with no operational problems - but the case of the appliance will be electrically 'hot'. This is a dangerous situation. Large appliances with 3 wire plugs - plugged into a properly grounded 3 wire circuit - would then blow a fuse or trip a circuit breaker. However, small appliances like toaster, broilers, irons, etc., have two wire plugs and will just set there with a live cabinet.
Testing: Visually inspect for bare wires or wires with frayed or worn insulation touching metal parts, terminals they should not be connected to, or other wires. Use a multimeter on the high ohms scale to check between both prongs of the AC plug and any exposed metal parts. Try all positions of any power or selector switches. Any resistance measurement less than 100K ohms or so is cause for concern - and further checking. Also test between internal terminals and wires that should not be connected together.
Too many people like to blame everything from blown light bulbs to strange noises on short circuits. A 'slight', slow, or marginal short circuit is extremely rare. Most short circuits in electrical wiring between live and neutral or ground (as opposed to inside appliances where other paths are possible) will blow a fuse or trip a breaker. Bad connections (grounds, neutral, live), on the other hand, are much much more common.
Testing: Where there is a changed feel to the switch or thermostat with an associated operational problem, there is little doubt that the part is bad and must be replaced. Where this is not the case, label the connections to the switch or thermostat and then remove the wires. Use the continuity checker or ohmmeter across each set of contacts. They should be 0 ohms or open depending on the position of the switch or knob and nothing in between. In most cases, you should be able to obtain both readings. The exception is with respect to thermostats where room temperature is off one end of their range. Inability to make the contacts open or close (except as noted above) or erratic intermediate resistances which are affected by tapping or jiggling are a sure sign of a bad set of contacts.
Testing: If the appliance does not run but there is a hum (AC line operated appliances) or runs sluggishly or with less power than you recall when new, lubrication problems are likely. With the appliance unplugged, check for free rotation of the motor(s). In general, the shaft sticking out of the motor itself should turn freely with very little resistance. If it is difficult to turn, the motor bearings themselves may need attention or the mechanism attached to the motor may be filled with crud. In most cases, a thorough cleaning to remove all the old dried up and contaminated oil or grease followed by relubing with similar oil or grease as appropriate will return the appliance to good health. Don't skimp on the disassembly - total cleaning will be best. Even the motor should be carefully removed and broken down to its component parts - end plates, rotor, stator, brushes (if any) in order to properly clean and lubricate its bearings. See the appropriate section of the chapter: Motors 101 for the motor type in your appliance.
Testing: Except for the case of a vacuum cleaner where the belt is readily accessible, open the appliance (unplugged!). A good rubber belt will be perfectly elastic and will return to its relaxed length instantly when stretched by 25 percent and let go. It will not be cracked, shiny, hard, or brittle. A V-type belt should be dry (no oil coating), undamaged (not cracked, brittle, or frayed), and tight (it should deflect 1/4" to 1/2" when pressed firmly halfway between the pulleys).
Sometimes all that is needed is a thorough cleaning with soap and water to remove accumulated oil or grease. However, replacement will be required for most of these symptoms. Belts are readily available and an exact match is rarely essential.
Testing: In many cases, the problem will be obvious. Where it is not, some careful detective work - putting the various mechanisms through their paces - should reveal what is not functioning. Although replacement parts may be available, you can be sure that their cost will be excessive and improvisation may ultimately be the best approach to repair. See the section: Fil's tips on improvised parts repair.
The result may be any of the items listed in (1) to (7) above. Once the actual contamination has been removed and the area cleaned thoroughly, inspect for damage and repair as needed. If the appliance failed while powered, you may also have damage to wiring or electronic components due to any short circuits that were created by the intruders' activities.
The following types of parts are found in line powered appliances:
CAUTION: Some cordsets are more than what meets the eye. See the section: When a cordset is more than a cord and plug.
Most plug-in appliances in the U.S. will have one of 3 types of line cord/plug combinations:
Thus, if you are replacing a plug and don't know (or didn't label) how the old one was hooked up, the narrow prong should go to the fuse, switch, thermostat or other control, center of the socket, etc. Since you may have trouble finding non-polarized plugs these days, this applies to older appliances as well and there is really no problem in replacing a non-polarized plug with a polarized one on an appliance.
Light duty cordsets are acceptable for most appliances without high power heating elements or heavy duty electric motors. These include table lamps, TVs, VCRs, stereo components, computers, dot matrix and inkjet printers, thermal fax machines, monitors, fans, can openers, etc. Electric blankets, heating pads, electric brooms, and food mixers are also low power and light duty cordsets are acceptable. The internal wires used is #18 AWG which is the minimum acceptable wire size (highest AWG number) for any AC line powered device.
Medium or heavy duty cordsets are REQUIRED for heating appliances like electric heaters (both radiant and convection), toasters, broilers, steam and dry irons, coffee makers and electric kettles, microwave and convection ovens, laser printers, photocopiers, Xerographic based fax machines, canister and upright vacuum cleaners and shop vacs, floor polishers, many portable and most stationary power tools. The internal wires used will be #16 AWG (medium duty) or #14 AWG (heavy duty).
For replacement, always check the nameplate amps or wattage rating and use a cordset which has a capacity at least equal to this. The use of an inadequate cordset represents a serious fire hazard.
Three prong grounded cordsets are required for most computer equipment, heavy appliances, and anything which is not double insulated and has metal parts that may be touched in normal operation (i.e., without disassembly).
The individual wires in all cordsets except for unpolarized types (e.g., older lamp cord) will be identified in some way. For sheathed cables, color coding is used. Generally, in keeping with the NEC (Code), black will be Hot, white will be Neutral, and green will be Safety Ground. You may also find brown for Hot, blue for Neutral, and green with a yellow stripe for Safety Ground. This is used internationally and is quite common for the cordsets of appliances and electronic equipment.
For zip cord with a polarized plug, one of the wires will be tagged with with a colored thread or a ridge on the outer insulation to indicate that it is the Neutral wire. For unpolarized types, no identification is needed (though there still may be some) as the wires and prongs of the plug are identical. However, fewer and fewer devices use non-polarized cords/plugs now so you are more likely to see this with older ones.
In general, when replacement is needed, use the same configuration and length and a heavy duty type if the original was heavy duty.
If the input is completely symmetric (e.g., it goes into a power transformer and no where else), then the polarity doesn't matter.
Before disconnecting the old cord, label connections or make a diagram and then match the color code or other wire identifying information. In all cases, it is best to confirm your final wiring with a continuity tester or multimeter on the low ohms scale. Mistakes on your part or the manufacturer of the new cord are not unheard of!
Common problems: internal wiring conductors broken at flex points (appliance or plug). With yard tools, cutting the entire cord is common. The connections at the plug may corrode as well resulting in heating or a broken connection.
Testing: Appliance cordsets can always be tested with a continuity checker or multimeter on a the low ohms scale.
Squeeze, press, spindle, fold, mutilate the cord particularly at both ends as while testing to locate intermittent problems.
If you are too lazy to open the appliance (or this requires the removal of 29 screws), an induction type of tester such as used to locate breaks in Christmas tree light strings can be used to confirm continuity by plugging the cord in both ways and checked along its length to see if a point of discontinuity can be located. A permanent bench setup with a pair of outlets (one wired with reverse polarity and clearly marked: FOR TESTING ONLY) can be provided to facilitate connecting to either of the wires of the cordset when using an induction type tester.
Note: broken wires inside the cordset at either the plug or appliance end are among the most common causes of a dead vacuum cleaner due to abuse it gets - being tugged from the outlet, vacuum being dragged around by the cord, etc. Many other types of appliances suffer the same fate. Therefore, checking the cord and plug should be the first step in troubleshooting any dead appliance.
If the cord is broken at the plug end, the easiest thing to do is to replace just the plug. A wide variety of replacement plugs are available of three basic types: clamp-on/insulation piercing, screw terminals, and wire compression.
Of course, if the problem is with an *extension* cord, then either it is overloaded or defective. In either case, the solution should be obvious.
Some cords will run warm just by design (or cheapness in design using undersized conductors).
However, if it is gets hot during use, this is a potential fire hazard.
If it is hot mainly at the plug end - get a heavy duty replacement plug - one designed for high current appliances using screw terminals - at a hardware store, home center, or electrical supply house. Cut the cord back a couple of inches.
If the entire cord gets warm, this is not unusual with a heater. If it gets really hot, the entire cord should be replaced. Sometimes with really old appliance, the copper wires in the cord oxidize even through the rubber insulation reducing their cross section and increasing resistance. This leads to excessive power dissipation in the cord. Replacement *heavy duty* cordsets are readily available.
Note that just because the cord itself gets warm does NOT mean that the wiring in the walls is heating significantly. The smallest allowable wiring size inside the walls is #14 which has a resistance of about 2.5 ohms per thousand feet. An appliance drawing 10 A through 50 feet of cable (100 total feet of wire going both ways) would result in a 2.5 V drop and 25 W dissipation. But since this is distributed over 50 feet of cable, heating in any location is minimal.
Extension cord rules of use:
Common problems: internal wiring conductors broken at flex points (socket or plug). With yard tools, cutting the entire cord is common. The connections at the plug may corrode as well resulting in heating or a bad or intermittent connection.
Testing: Extension cords can always be tested with a continuity checker or multimeter on a the low ohms scale.
But, how do you locate the break?
This also works for appliance cords where you are too lazy to go inside to check continuity. You may need to try both wires in the cord to locate the broken one.
An AM or multiband radio may also be suitable as a detector.
Inside the appliance, individual wires (often multicolored to help identify function) or cables (groups of wires combined together in a single sheath or bundle) route power and control signals to the various components. Most are insulated with plastic or rubber coverings but occasionally you will find bare, tinned (solder coated), or plated copper wires. In high temperature appliances like space heaters and toasters, the insulation (if present) will be asbestos (older) or fiberglass. (Rigid uninsulated wires are also commonly found in such applications.) Particles flaking off from either of these materials are a health hazard if you come in contact, inhale, or ingest them. They are also quite fragile and susceptible to damage which may compromise their insulating properties so take care to avoid excessive flexing or repositioning of wires with this type of insulation. Fiberglass insulation is generally loose fitting and looks like woven fabric. Asbestos is light colored, soft, and powdery.
Color coding will often be used to make keeping track of the wires easier and to indicate function. However, there is no standard except for the input AC line. Generally, black will be used for Hot, white will be used for Neutral, and green or uninsulated wire will be used for Safety Ground. While this is part of the NEC (Code) for electrical wiring (in the U.S.), it is not always followed inside appliances. You may also find brown for Hot, blue for Neutral, and green with a yellow stripe for Safety Ground. This is used internationally and is quite common for the cordsets of appliances and electronic equipment.
Where a non-polarized plug (cordset) is used, either AC wire can be Hot and both wires will typically (but not always) be the same color.
Other colors may be used for switched Hot (e.g., red), thermostat control, motor start, solenoid 1, etc. Various combinations of colored stripes may be used as well. Unfortunately, in some cases, you will find that all the wiring is the same color and tracing the circuit becomes a pain in the you-know-what.
Where multiple wires need to go from point A to point B along the same path, they will often be combined into a single cable which is bundled using nylon or cloth tie-wraps or run inside a single large flexible plastic sheath. For electronic interconnects and low voltage control and signal wiring, molded flat cables are common (like those for the cables to the diskette and hard drives of your PC). These are quite reliable and can be manufactured at low cost by fully automatic machines.
The thickness of the insulation of a wire or cable is not a reliable indication of its capacity or voltage rating. A fat wire may actually have a very skinny central conductor and vice-versa. In some cases, the wire conductor size and voltage rating will be printed on the insulation but this not that common. If replacement is needed, this information will be essential. However, the ampacity (maximum current) can be determined from the size of the metal conductor and for any of the line powered appliances discussed in this document, wire with a 600 V rating should be more than adequate.
The type of insulation is critical in appliances that generate heat - including table lamps and other lighting fixtures. There is special high temperature insulated wire (fixture wire) which should be used when replacement is needed. For heating appliances like toasters, hair dryers, and deep friers, fiberglass or high temperature silicone based rubber insulated wire or insulating sleeves must be used should the original wiring need replacement. An appliance repair motor rebuilding shop would be the most likely source - common electronics distributors may not carry this stuff (especially if you only need a couple feet)!
Connections between individual wires and between individual wires and other components are most often made by crimp or screw terminals, welding, or press-in contacts. For cables, actual multipin and socket connectors may be used.
Common problems: internal wiring conductors broken, corroded, or deteriorated due to heat or moisture. Dirty, corroded, weakened, or damaged connector contacts are common requiring cleaning and reseating or replacement. Damage to insulation from vibration, heat, movement, or even improper manufacture or design is also possible. Careless reassembly during a previous repair could result in pinched broken wires or insulation as well as short circuits between wires, or wiring and sharp sheet metal parts.
Testing: Inspect for obvious breaks or wires that have pulled out of their terminations. Integrity of wiring can be determined with a continuity checker or multimeter on a the low ohms scale. Flexing and wiggling wires especially at connections while observing the meter will identify intermittents.
Testing: Switches can always be tested with a continuity checker or a multimeter on a low ohms scale.
WARNING: Mercury is a heavy metal and is poisonous. I know it is fun to play with beads and globs of the stuff (and I have done it) but do not recommend it, at least not on a daily basis. Dispose of any from broken mercury switches or thermometers safely. If you insist on keeping it, use a piece of paper as a scoop and put the mercury in a bottle with a tightly sealed cap. See the section: Comments on mercury poisoning.
Problems are rare with these mercury switches. In fact, GE mercury switches used to carry a *50* year warranty! I don't know if they still do.
In principle, these are also the safest type of switch since any sparking or arcing takes place inside the sealed mercury capsule. However, the contact between the screw terminals and the capsule are via sliding contacts (the capsule is press fit between the metal strips to which the screws are attached) and with time, these can become dirty, worn, or loose. For this reason, some electricians do not like mercury switches, particularly for high current loads.
The danger isn't so much from occasional contact with metallic mercury as from mercury vapor which may build up in an enclosed spaces and from soluble mercury compounds. You get significant contact with metallic mercury from amalgam ("silver") tooth fillings and while there is controversy about their safety and some people have had their old fillings ripped out at great expense (and disconfort!), there is as far as I know, no conclusive scientific evidence linking mercury poisoning to amalgam fillings.
Having said that, I agree that it's probably a bad idea to be playing with mercury on a daily basis but pushing a few drops of it around or losing one drop to the floorboards isn't going to make everyone sick. If this were the case, half the houses in the World would be HAZMAT zones from broken fluorescent lamps - which have significant metallic mercury in them.
If anyone has evidence to the contrary, please cite refereed scientific publications and I will read them, not hyped popular press reports.
The most common types are:
A ______/ _______ B
This is the normal light or power switch. For electrical (house) wiring, it may be called a '2-way' switch.
A ______/ _______ B
:
C ______/ _______ D
This is often used as a power switch where both wires of the AC line are switched instead of just the Hot wire.
_______ NC
C ______/
_______ NO
This is the same configuration as what is known as a '3-way' switch for electrical (house) wiring. Two of these are used to control a fixture from separate locations.
_______ NC1
C1 ______/
: _______ NO1
:
: _______ NC2
C2 ______/
_______ NO2
_________ 1
_______ 2
C ______/ ______ 3
_______ 4
_________ 5
Fuses use a fine wire or strip (called the element) made from a metal which has enough resistance (more than for copper usually) to be heated by current flow and which melts at a relatively low well defined temperature. When the rated current is exceeded, this element heats up enough to melt (or vaporize). How quickly this happens depends on the extent of the overload and the type of fuse.
Fuses found in consumer electronic equipment are usually cartridge type - 1-1/4" mm x 1/4" or 20 mm x 5 mm, pico(tm) fuses that look like green 1/4 W resistors, or other miniature varieties. Typical circuit board markings are F or PR.
More than you could ever want to know about fuses can be found at the Littlefuse Web site. Go to Resouces->Reference Materials->Fusology to start.
Circuit breakers may be thermal, magnetic, or a combination of the two. Small (push button) circuit breakers for appliances are nearly always thermal - metal heats up due to current flow and breaks the circuit when its temperature exceeds a set value. The mechanism is often the bending action of a bimetal strip or disc - similar to the operation of a thermostat. Flip type circuit breakers are normally magnetic. An electromagnet pulls on a lever held from tripping by a calibrated spring. These are not usually common in consumer equipment (but are used at the electrical service panel).
At just over the rated current, it may take minutes to break the circuit. At 10 times rated current, the fuse may blow or circuit breaker may open in milliseconds.
The response time of a 'normal' or 'rapid action' fuse or circuit breaker depends on the instantaneous value of the overcurrent.
A 'slow blow' or 'delayed action' fuse or circuit breaker allows instantaneous overload (such as normal motor starting) but will interrupt the circuit quickly for significant extended overloads or short circuits. A large thermal mass delays the temperature rise so that momentary overloads are ignored. The magnetic type breaker adds a viscous damping fluid to slow down the movement of the tripping mechanism.
Common problems: fuses and circuit breakers occasionally fail for no reason or simply blow or trip due to a temporary condition such as a power surge. However, most of the time, there is some other fault with the appliance which will require attention like a bad motor or shorted wire. Dirty, corroded, or weak contacts (holding the fuse or circuit breaker) may get hot and contribute to nuisance tripping. Circuit breakers can also go bad just due to age (this particularly applies to those in the electrical service panel - one that buzzes and/or trips occasionally for no apparent reason may need replacement).
Testing: Fuses and circuit breakers can be tested for failure with a continuity checker or multimeter on the low ohms scale. A fuse that tests open is blown and must be replaced (generally, once the circuit problem is found and repaired.) Of course, if the fuse element is visible, a blown fuse is usually easy to identify without any test equipment. A circuit breaker that tests open or erratic after the reset button is pressed, will need replacement as well.
Note that in general, circuit breakers should NOT be used for repeated switching nor should they be reset on a circuit with any substantial load (or overload or short circuit). Their contacts are not designed for this type of operation. Here are some additional comments:
(From: Tom Hardy (th7675@istate.net).)
Many people use circuit breakers as switches (including my father-in-law!). The problem is that the contacts become burned, creating resistance and thus abnormal heating causing the breaker to be unable to carry its rated load. The other thing this does (especially with Square-D QO style breakers) through heating is causes the buss bar contact to loose it's spring tension (in reference to circuit breakers installed in an electrical service panel). This will (as happened to my father-in-law) burn up part of the buss bar and ruin the electric panel. Most people will just reset a breaker if it trips, without first removing the load. This also causes burned contacts as mentioned above. I have found many defective breakers before they go bad, usually feeding higher current appliances. Just turn on the appliance for 15 to 20 minutes and then feel the front of the breaker with your hand. If its warm or hot, there is usually reason to suspect future trouble if it's not replaced.
This information can be of use in directly further troubleshooting.
Even with circuit breakers, a short circuit may so damage the contacts or totally melt the device that replacement will be needed.
Five major parameters characterizes a fuse or circuit breaker:
Some equipment may use fuses with strange current ratings like 1.65 A instead of 1.5 A. In such cases, it won't hurt to try a common lower current value like 1.5 A. The worst that will happen is that it will blow, probably not immediately but some time in the future even if there is no problem. Using the next higher common value like 1.75 A isn't recommended except for testing. The irony is that these strange values are often used in the primaries of switchmode power supplies where their function is to blow due to catastrophic failure, not a slight overload, and it really doesn't matter if they are slightly larger (but only slightly larger!). However, for reasons of liability, this is still not recommended. Don't do it!
And, it's quite likely that there will be no difference between 125 V and 250 V fuses except the labeling. It really doesn't cost more to make higher voltage fuses in the same package size of the type found in consumer electronic equipment so any labeling like this would be more of a regulatory issue.
For high voltage, current limited equipment (up to 500 V or more, up to 10 times the fuse current rating), it may still be acceptable to use a 250 V fuse.
However, any soldering of wires directly to a fuse should be done with care and it may weaken the fuse element or its connection if the fuse doesn't just fall apart. Thus, where soldered-in fuses are used, obtain replacements with wire leads that preattached or solder in a fuse holder.
There are three typical types:
CAUTION: When replacing a thermal fuse, DO NOT SOLDER it if at all possible. If the device gets too hot, it may fail immediately or be weakened. Crimp or screw connections are preferred. It is normally possible to obtain "crimp rings" when you order - they may be included. Then, just cut off the old fuse but leave some wire, slip the old and new wires into a crimp ring (twist them for added mechanical stability) and compress the ring tightly with a pair of pliers. Note the direction: If the appliance uses a polarized plug, it is recommended that the isolated lead of the thermal fuse be attached to the Hot AC wiring and the bare metal body of the thermal fuse which is connected to one lead be attached to the wiring of the appliance. This is a minor point but it doesn't cost anything!
* *
To AC Hot -------||-- ______ --||-------- To appliance wiring
--||------<______|------||--
New Thermal Fuse
* Twisted and crimped connection for maximum mechanical strength.
If you must solder, use a good heat sink (e.g., wet paper towels, little
C-clamps) on the leads between the thermal fuse and the soldering iron, and
work quickly!
In some applications, device types (2) and (3) may be used as the primary temperature regulating controls where adjustment is not needed with (1) as the protection of last resort. For example, a hair dryer may depend on air-flow to maintain the desired temperature. But it will have a bimetal strip-type thermostat to shut off power if the air-flow is blocked for some reason and a thermal fuse to permanently disable the device should the thermostat fail to open.
For testing, it is perfectly acceptable to temporarily short out the device to see if the equipment then operates normally without overheating. This will confirm that a one-time thermal fuse has blown, or that a resettable type is malfunctioning. However, while these devices do sometimes just fail on their own, most likely, there was another cause. If you know what it was - you were trying to charge a shorted battery pack, using your window fan to mix cement, or something was shorted externally, then the fuse served its protective function and the equipment is fine. IT SHOULD BE REPLACED WITH THE SAME TYPE or the entire transformer, motor, or whatever it was in should be replaced! This is especially critical for unattended devices. Otherwise, especially with unattended devices, you have a situation where if the overload occurred again or something else failed, the equipment could overheat to the point of causing a fire - and your insurance company may refuse to cover the claim if they find that a change was made to the circuit. And even for portable devices like blow dryers and portable power tools, aside from personal safety should the device malfunction, the thermal protector is there to prevent damage to the equipment itself - don't leave it out!
The following is From Microtemps' literature (`95 EEM Vol.B p1388):
"The active trigger mechanism of the thermal cutoff (TCO) is an electrically non-conductive pellet. Under normal operating temperatures, the solid pellet holds spring loaded contacts closed. When a pre-determined temperature is reached, the pellet melts, allowing the barrel spring to relax. The trip spring then slides the contact away from the lead and the circuit is opened. Once TCO opens a circuit, the circuit will remain open until the TCO is replaced....."
Be very careful in soldering these. If the leads are allowed to get too hot, it may "weaken" the TCO, causing it to fail prematurely. Use a pair of needle-nose pliers as heat sinks as you solder it.
I have replaced a few of these in halogen desk lamp transformers. The transformers showed no signs of overheat or overload. But once I got it apart, the TCO's leads had large solder blobs on them, which indicated that the ladies that assembled the transformers must have overheated the cutouts leads when they soldered them.
The NTE replacement package also comes with little crimp-rings, for high-temp environments where solder could melt or weaken (or to avoid the possibility of soldering causing damage as described above --- sam).
Four types are typically found in appliances. The first three of these are totally mechanically controlled:
In a thermostat, the bimetal strip operates a set of contacts which make or break a circuit depending on temperature. In some cases the strip's shape or an additional mechanism adds 'hysteresis' to the thermostat's characteristics (see the section: What is hysteresis?).
Testing of mechanical thermostats: Examine for visible damage to the contacts. Use a continuity checker or ohmmeter to confirm reliable operation as the knob or slider is moved from end to end if it will switch at room temperature. Gently press on the mechanism to get the contacts to switch if this is not possible. Use an oven on low or a refrigerator or freezer if needed to confirm proper switching based on temperature.
Humidistats, as their name implies, are used to sense relative humidity in humidifiers and dehumidifiers. Their sensing material is something that looks kind of like cellophane or the stuff that is used for sausage casings. It contracts and expands based on the moisture content of the air around it. These are somewhat fragile so if rotating the control knob on a humidifier or dehumidifier does not result in the normal 'click', this material may have been damaged or broken.
Testing of mechanical humidistats: examine for visible damage to the contacts. Use a continuity checker or ohmmeter to confirm reliable operation as the knob or slider is moved from end to end. Gently press on the mechanism to get the contacts to switch if this is not possible. Gently exhale across the sensing strip to confirm that the switching point changes.
Examples of systems with hysteresis:
B o-------------+
|
V
A o--------/\/\/\/\/\-----
250 ohm rheostat
In the diagram above, the resistance changes smoothly from 0 to 250 ohms as the wiper moves from left to right.
Very often, you will see the following wiring arrangement:
B o-------------+------+
| |
V |
A o--------/\/\/\/\/\--+
250 ohm rheostat
Electrically, this is identical. However, should the most common failure occur with the wiper breaking or becoming disconnected, the result will be maximum resistance rather than an open circuit. Depending on the circuit, this may be preferred - or essential for safety reasons.
Testing: Disconnect at least one of the terminals from the rest of the circuit and then measure with an ohmmeter on the appropriate scale. The resistance should change smoothly and consistently with no dead spots or dips.
B o-------------+
|
V
A o--------/\/\/\/\/\--------o C
1K ohm potentiometer
In the diagram above, the resistance between A and B varies smoothly from 0 to 1K ohms as the wiper moves from left to right. At the same time, the resistance between B and C varies smoothly from 1K to 0 ohms. For some applications, the change is non-linear - audio devices in particular so that the perceived effect is more uniform across the entire range.
Testing: Disconnect at least two of the terminals from the rest of the circuit and then measure with an ohmmeter on the appropriate scale. The resistance should change smoothly and consistently with no dead spots or dips. Try between each end and the wiper. Check the resistance across the end terminals as well - it should be close to the stamped rating (if known).
Testing: Use an ohmmeter or continuity checker on the switches. The reading should either be 0 ohms or infinite ohms. Anything in between or erratic behavior is indication of a bad switch or cord.
Testing: Use an ohmmeter or continuity check to confirm that both wires of the cord are connected to both AC plug and appliance connector. Wiggle the cord where it connects to the appliance and at the plug end as well to see if there might be broken wires inside.
Testing: visual inspection will often reveal a burnt out incandescent light bulb simply because the filament will be broken. If this is not obvious, use an ohmmeter - an infinite resistance means that the bulb is bad.
See the chapter: Incandescent Light Bulbs, Lamps, and Lighting Fixtures for more info.
Small fluorescent lamps are often found in makeup mirrors, plant lights, and battery powered lanterns.
Testing: The best test for a bad fluorescent lamp (tube) is to substitute a known good one. Unfortunately, there is no easy go-no go test for a these as with an incandescent lamp. Other parts of the fixture (like the ballast or starter) could also be bad. Testing with a multimeter between the pair of pins at each end should show low resistance if the lamp is good. However, depending on the type of ballast, a lamp with an open filament may still work just fine even though strictly speaking, it is defective. Again, try a replacement to be sure. CAUTION: A defective ballast or starter can cause a fluorescent lamp to go bad in short order - if it still doesn't work, don't just let it continue to try to start!
See the document: Fluorescent Lamps, Ballasts, and Fixtures for additional information.
There are three common types of electrical indicator lights:
Incandescent indicator lamps are often removable using a miniature screw, bayonet, or sliding type base. Some are soldered in via wire leads. Others look like cartridge fuses.
Testing: Visual inspection will often reveal a burnt out incandescent light bulb simply because the filament will be broken. If this is not obvious, use an ohmmeter - an infinite resistance is means that the bulb is bad.
They are nearly all the characteristic orange neon color although other colors are possible and there is a nice bright green variety with an internal phosphor coating that can actually provide some illumination as well. While neon bulbs do not often burn out in the same sense as incandescent lamps, they do darken with age and may eventually cease to light reliably so flickering of old Neon bulbs is quite common. This is almost always just due to the natural aging process of the indicator and does not mean the outlet or appliance itself is bad.
Some Neon bulbs come in a miniature bayonet base. Most are soldered directly into the circuit via wire leads.
Testing: Inspect for a blackened glass envelope. Connect to AC line (careful - dangerous voltage) through a series 100K resistor. If glow is weak or absent, Neon bulb is bad.
LEDs are almost always soldered directly into the circuit board since they rarely need replacement.
As an item of interest which has nothing to do with appliance repair, many automotive tail lights are now red LEDs, particularly the middle brake light. In fact, the red (stop) lights in many traffic signals are now LED clusters that screw directly into a normal 115 VAC socket. This is done because one of these will outlast 50 normal incandescent lamps and the cost of replacement far exceeds the cost of the lamp itself. How can you tell which type is used? Easy, move your eyes (or head) from side-to-side while looking at the red light; since the LED actually pulses 120 times per second (for 60 Hz power), you will see a series of spots - an incandescent lamp will appear continuous. Yellow and green will probably follow shortly but all I've seen so far are the red ones using LEDs.
Testing: Use a multimeter on the diode test scale. An LED will have a forward voltage drop of between 1.7 and 3 V. If 0 or open, the LED is bad. However, note: some DMMs may not produce enough voltage on the diode test scale so the following is recommended: Alternative: Use a 6 to 9 V DC supply in series with a 470 ohm resistor. LED should light if the supply's positive output is on the LED's anode. If in doubt, try both ways, If the LED does not light in either direction, it is bad.
Testing: Check for bad connections and bad components with a multimeter. An open series resistor, shorted EL device, or faulty (partially shorted) MOV is possible. However, sometimes these failures won't show up except when normal voltage is applied. Measure on the AC volts range across the EL device - there should be a high AC reading, probably over 100 VAC.
There are 3 basic types of heating elements. Nearly every appliance on the face of the planet will use one of these:
NiChrome coils are used in many appliances including toasters, convection heaters, blow-dryers, waffle irons and clothes dryers.
The main disadvantage for our purposes is that it is usually not possible to solder this material due to the heating nature of its application. Therefore, mechanical - crimp or screw must be used to join NiChrome wire or ribbon to another wire or terminal. The technique used in the original construction is may be spot welding which is quick and reliable but generally beyond our capabilities.
Testing: Visual inspection should reveal any broken coil or ribbon. If inspection is difficult, use a multimeter on the low ohms scale. Check for both shorts to the metal chassis as well as an open element (infinite ohms).
These are found in toaster oven/broilers, hot plates, coffee makers, crock pots and slow cookers, electric range surface elements, conventional and convection ovens and broilers.
Testing: When these fail, it is often spectacular as there is a good chance that the internal NiChrome element will short to the outer casing, short out, and melt. If there is no visible damage but the element does not work, a quick check with an ohmmeter should reveal an open element or one that is shorted to the outer casing.
These are found in various kinds of radiant heaters. By running a less than maximum power - more orange heat - the peak radiation is in the infra-red rather than visible range.
Testing: Look for a broken filament. Test with an ohmmeter just like an incandescent light bulb.
I have used nuts and bolts, say 6-32, bolt, wire, washer, wire, washer, lockwasher, nut. Depending on how close to the actual really hot element it is, this may work. If you are connecting to the coiled element, leave a straight section near the joint - it won't get as hot.
The use of high temperature solder or brazing might also work.
The best approach is probably to use high temperature crimp connectors:
(The following from: sad@garcia.efn.org (Stephen Dunbar))
You can connect heating element wires with high-temperature solderless connectors that are crimped onto the wires. Be sure to get the special high-temp connectors; the ordinary kind will rapidly oxidize and fall apart at high temperatures. If you want to join two wires to each other, you'll need either a butt splice connector (joins the wires end-to-end) or a parallel splice connector (the wires go into the connector side-by-side). To fasten a wire to a screw terminal you can use a ring or spade connector (though as noted above, a screw, nut, and washer(s) should work fine --- sam). If your waffle iron has quick disconnect terminals you'll need the opposite gender disconnect (AkA Faston). These come in both .187" and .250" widths.
Your best bet for getting these connectors in small quantity is probably a local appliance parts outlet that caters to do-it-yourselfers. If you can't find what you need there, try Newark Electronics (branches all over the place). I have an old copy of their catalog which lists SPC Technology Voltrex Brand High Temperature Barrel Terminals in several styles: ring, spade, disconnect, and butt splice. The prices were around $10 to $12 per 100 (this catalog is a couple of years old) for wires in the 22-18 or 16 to 14AWG size ranges, almost twice that for the heftier wire gauges. (Be sure to determine the wire gauge of your heating elements so you can get the right size terminal.)
You can spend a *lot* of money on crimp tools, but for occasional light use you can probably get by with one of those $10 gadgets that crimp, strip & cut wires, and cut bolts--the sort of thing you'd find in your local home center or Radio Shack.
(From: Nigel Cook (diverse@tcp.co.uk).)
The thin stainless steel strip found spot welded to multicell NiCd batteries make good crimps for joining breaks in heater resistance wire. Form a small length of this strip around a needle or something similar to make a tight spiral with enough clearance to go over doubled-up heater wire. Abraid or file the cut ends of the broken wire. Crimp into place with a double lever action crimper. If there is an area of brittle heating element around the break then cut out and splice in a replacement section with two such crimps. Such a repair to my hot-air paint stripper (indispensable tool in my electronics tool-kit) has survived at least 50 hours.
(From: Dan Sternberg (steberg@erols.com).)
Another old trick for nichrome repair is to make a paste of Borax, twist the two broken end together, and energize the circuit. A form of bond welding takes place. I've have used this on electric clothes dryer heater elements with good luck.
(From: DaveC.)
Here's a "quick fix" that sometimes works for a long time and sometimes fails quickly (depending, I think, on just how old and brittle the nichrome wire is).
Mix some ordinary "Boraxo" powdered hand soap with a little water to make a thick paste -- and you don't need much.
Take the broken ends of wire, bend a small loop into each, and interlock the loops so the wires stay together.
Pack the Boraxo paste around the joint, and turn on the heater.
Keep your eyes on that joint. As the coil heats up, the hook joint will be the worst connection, so it'll naturally get the hottest.
When it gets hot enough, the nichrome wires will melt, and, being fluxed by the borate, will fuse together into a blob. The blob, now being *larger* than the rest of the wires, will immediately cool down, and will never again get as "red hot" as the rest of the heater.
Allow the coils to cool down and, using pliers, carefully crush any glassy flux deposit that remains on the joint.
If the joint doesn't behave as I describe, or if the wires are too brittle to be formed into hooks, the wires are likely too old to produce a long-lasting joint. If the joint behaves as I described, it may last for a good long time.
Solenoids are usually two position devices - they are not used to provide intermediate amounts of force or travel like motors.
Sizes ranges from small 1/2" long units providing a fraction of an ounce of force and 1/8" travel to large 3" long units providing many pounds of force with travels of 2" or more.
Testing: Inspect for free movement. Use an ohmmeter to confirm that the coil is intact. There could be other problems like shorted turns in the coil but these would be less common than lack of lubrication or an open coil. Check voltage on operating solenoid to determine whether drive power is present.
Transformers are used in nearly every type of electronic equipment both for power and signals, and throughout the electrical distribution network to optimize the voltage/current used on each leg of the journey from the power plant to the user.
The types we are interested in with respect to household appliances and power tools are most often use to convert the AC line voltage to some other value, lower or higher:
Motors come in all shapes and sizes but most found in small appliances can be classified into 5 groups:
There are two primary types of configurations:
The direction of the air movement with respect to blade rotation is determined by the pitch - the tilt - of the blades. Although reversing air direction is possible by reversing the motor, one direction is usually more effective than the other due to the curve of the blades.
Direction of rotation of the blower motor does not change the direction of airflow. However, one direction will be more effective than the other (where the blower is rotating in the same direction as the way exit port on the air plenum points. Because of this, it is not possible for a vacuum cleaner to blow out the suction hose due to a reversed motor (which in itself is for all intents and purposes, impossible as well). This is usually caused by back flow due to a blockage.
Under normal conditions, a plain bearing wears only during start and stop cycles. While the shaft is rotating at any reasonable speed, there is no metal to metal contact and thus no wear. With a properly designed and maintained bearing of this type, a very thin oil film entirely supports the shaft - thus the importance of clean oil. Your automobile engine's crankshaft is entirely supported by these types of bearings.
Eventually, even 'lubricated for life' bearings of this type may need to be disassembled, cleaned, and lubricated. The plain bearings in small appliances must be lubricated using a proper light oil like electric motor or machine oil - not automotive engine oil and NEVER NEVER WD40.
NEVER, ever, use WD40 as a lubricant (unless specifically recommended by the manufacturer of the equipment, that is)! WD40 is not a good lubricant despite the claims on the label. Legend has it that the WD actually is an abbreviation for Water Displacer - which is one of the functions of WD40 when used to coat tools. WD40 is much too thin to do any good as a general lubricant and will quickly collect dirt and dry up. It is also quite flammable and a pretty good solvent - there is no telling what will be affected by this.
WD40 has its uses but lubrication unless specifically recommended by the manufacturer (of the equipment, that is) is not one of them. Results initially may be good with that instant gratification that comes from something returning to life. However, the lighter fractions of WD40 evaporate in a few days
For very small metal-in-plastic types, the following might be useful:
(From: Frank MacLachlan (fpm@bach.n2.net).)
"I've had good luck with a spray lubricant called SuperLube. It contains a solvent which evaporates and leaves a Teflon film which doesn't migrate or retain dust. I spray some into a spray paint cap and then apply the solution with a toothpick, allowing the lubricant to wick into the bearing areas. Worked great for some balky Logitech mice I purchased at a local swap meet."
Sometimes, reworking an appliance to use a ball bearing instead of a plain bearing is a worthwhile effort - I have done this with electric drills and shop vacs. They run smoother and quieter with ball bearings. Not surprisingly, higher-end models of these devices (which use ball bearings) share parts with the cheaper versions and finding standard ball bearings that would fit was not difficult.
Most of these are just small timing motors (synchronous motors running off of the AC line) which rotate one or more cams (disks with bumps) which activated one or more switches at appropriate times during the rotation cycle. Typical cycle times range from a minute or less to several hours (refrigerator defrost timer). Most like washing machine timers are in the 1 hour range. Sometimes, the motor is stopped during certain portions of the cycle awaiting completion of some other operation (i.e., fill).
These controllers therefore consist of several parts:
If some of the circuits do not work, check the switches for dirty or worn contacts or broken parts.
While generally quite reliable, bad solder connections are always a possibility as well as failed parts due to operation in an environment prone to temperature extremes.
Testing: Check for bad solder connections and connectors that need to be cleaned and reseated. Inspect for obviously broken or burned parts. Test components for proper value.
For digital clock/programmers or microprocessor based controllers, not much else can be done without a schematic - which not likely to be easily available.
The common table lamp is just a light duty cordset, switch, and sockets for one or more incandescent light bulbs. In many cases, the switch and socket are combined into one assembly. In other designs, particularly where more than one bulb can be lit independently (for example, a large bulb up top and a night light in the base), a separate switch (rotary or push-push) selects the light bulb(s) to be turned on.
For the most common combined switch and socket, there are several varieties and these are all generally interchangeable. Therefore, if you want to take advantage of the added convenience of a 3-way bulb allowing low, medium, and high illumination, it is a simple matter to replace the simple on-off switch in your lamp with a 3-way switch (not to be confused with the 3-way switches used in house wiring to control a single light fixture from 2 places).
Virtually the same switch/socket combo is used where there is a bulb in the top and the base. But instead of switching the extra contact inside a 3-way socket, that terminal goes to the bottom lamp holder.
Push-push, pull chain, and rotary switches are common for simple on-off control. The 3-way switches are usually of the rotary variety with off-low-medium-high selected as the knob is rotated. The 3-way bulb has two filaments which can be switched on individually or in combination to provide the 3 levels of illumination.
Dimmer sockets can often be substituted for the normal kind as long as conventional incandescent bulbs (and not compact fluorescents) are to be used.
Touch and even sound activated switch-sockets are also available though my personal recommendation is to stay away from them.
Most common problems: burned out bulb, worn switch, bad plug or cord. Where the light flickers, particularly if jiggling or tapping on the switch has an effect, a bad switch is almost always the problem. Switch failure is more common when using high wattage bulbs but can occur just due to normal wear and tear.
Replacements for most common switches and sockets are readily available at large hardware stores, home centers, and electrical supply houses. It is best to take along the old switch so that an exact match (if desired) can be obtained. While the thread sizes for the screw on socket shells are quite standard, some older lamps may have an unusual size. For more complicated switches with multiple sockets, label or otherwise record the wiring. If color coded, cut the wires so that the colors are retained at both the lamp and switch ends.
This is assumed to be the type of lamp which has a combination socket and switch with a metal (brass-colored usually) outer shell. It is your decision as to whether a simple on-off switch or a 3-way type is to be used - they are usually interchangeable and a normal light bulb can be put into a 3-way socket (two clicks of the knob will be needed to switch a normal light bulb on or off, however). You can also put a 3-way bulb into a normal socket but you will, of course, only get one level of illumination (medium). For lamps with lighted bases, also see the section: Lamps with night-light bulbs in their base.
You will need: (1) a new socket/switch of the appropriate type and (2) a new cordset (if you want to replace this as well). A polarized type plug is desirable to minimize the possibility of shock when changing bulbs. A medium size straight blade screwdriver and wire strippers are the only required tools.
This is a standard, if somewhat unusual socket. It is basically the same as a 3-way type but with the extra connection going to the bulb in the base of the lamp. In the old days when sockets were assembled with screws instead of rivets, it might have been possible to modify a new 3-way socket to provide the extra connection.
An electrical supply parts distributor or lamp store should have what you need or be able to order it for you.
Take note of the connections as you remove the old socket to avoid mistakes. When routing the wires to the bulb in the base, avoid allowing the hot bulb from contacting the insulation - the plastic stuff might melt (for a 7 W or less wattage bulb and high temperature insulation is probably not an issue, however).
Then, DON'T tighten the bulbs down all the way - just so they are a snug fit in the socket.
If a dimmer control is present, keep in mind that these are somewhat more sensitive to slight voltage fluctuations especially when set at low levels. You may simply not have noticed any flickering with a normal on/off switch.
Tensor(tm) (and their clones) high intensity lamps have been around for over 30 years and are essentially unchanged today. They use a low voltage transformer producing 12-24 VAC along with a special high output light bulb that looks similar to an automotive tail light. However, it uses substantially more current for the same voltage and puts out a much more intense, whiter light. These are not halogen lamps though their spectral characteristics are similar since the filaments run hotter than normal incandescents - and have shorter lives.
Some will have multiple levels of illumination based on selecting taps on the transformer. Normal dimmers may not work (and should not be used) with these due to their transformer design - damage to the dimmer or lamp may result and this may be a fire hazard.
Problems with Tensor lamps tend to center around the socket and switch. These may fail due to overheating as a result of the high temperature and high current operation. Replacements are available but they may take some effort to locate. A replacement lamp may be cheaper. (I often find complete Tensor lamps in perfect operating condition at garage sales for around $2.
Should the dimmer portion of such a fixture fail or become unreliable, it may a blessing in disguise since the lamp will either run at full intensity or can be easily rewired to do so by bypassing the electronics and just using the on/off switch!
WARNING: halogen bulbs run extremely hot and are a serious fire hazard and burn hazard if not properly enclosed. When changing a halogen bulb, wait ample time for the old one to cool or use an insulated non-flammable glove or pad to remove it. When installing the new bulb, make sure power is off, and do not touch it with your fingers - use a clean cloth or fresh paper towel. If you do accidentally touch it, clean with alcohol. Otherwise, finger oils may etch the quartz and result in early - possibly explosive failure - due to weakening of the quartz envelope.
(Source: The Associate Press except as noted).
Safety groups recommend the following precautions for owners of halogen torchere lamps with tubular bulbs:
Do not touch the new bulb with your fingers as the oils and acids may make them more prone to exploding. Clean the bulb thoroughly with isopropyl alcohol after any accidental contact (--- sam).
Note that this may not result in maximum life but will be safer due to the lower temperature of the bulb (--- sam).
These are susceptible to damage from voltage surges or just plain old random failures. In addition, the current surge that often results at the instant an incandescent bulb burns out (the bright flash) may blow the thyristor in the electronics module.
If the lamp is stuck on, the thyristor is probably shorted. The specific part can be replaced but to be sure it is bad, some testing will be needed and it is probably soldered in place. However, if you have repaired an ordinary lamp, you will be able to replace the entire module fairly easily.
If the lamp is stuck off, there could be a bad connection or bad bulb, or the electronics module is defective. Again, replacement is straightforward.
Erratic problems could be due to bad connections, dried up electrolytic capacitors (especially if the electronics module is near the hot bulb), or even external E/M interference (e.g., a dimmer or vacuum cleaner on the same circuit).
Some problems are of the following type:
"I have 2 touch lamps in the bed room and they are both plugged in to the same receptacle. Every once in a while the lamps come on by themselves for no apparent reason. Even more strange is that every so often just one lamp turns on by itself."
(From: Tim Moore (tmoore@interserf.net).)
These use a MOSFET type circuit to switch the lamps on and off. The circuit is attached to the metal in the lamp base. When you touch it the impedance changes ever so minutely but enough to change the MOSFET from off to on and visa versa. My wife could never get our lamps to switch, she often had to blow on her hand first to get it moist so it would make better contact. Here is part of the problem. It takes a certain amount of signal from the lamp base to switch the circuit. Electronic parts all have acceptable ranges of operation and when put into identical circuits they sometimes perform differently. One circuit might need a good hard touch while the other might need only a slight touch. Power surges would often switch one of my lamps, although it didn't happen often. A strong radio signal could do it too. The bottom line is that these lamps are not rocket science and can't be counted on as 100% reliable. Sorry, that's the truth. You give up a little to get the convenience of just having to touch them. I ended up removing mine - an electrical storm wiped one out and wiped the other out a few years later.
(Portions from: John Evans - N0HJ (jaevans@codenet.net).)
Here is a fix my buddy, Ed, a fellow ham radio operator, has come up with to solve this problem.
As usual it took 8 months and 10 minutes to fix.
Two parts: 1/4 watt, 1k Ohm resistor and 2.5 mH 1/2 watt size molded coil. Connect in-line with the touch wire.
I send 2 or more watts from my rig. My son works the CB.
You'll find it on when you get home.
So the darn thing is an oscillator which changes frequency when you touch it. The circuit does the rest. By adding the resistor/inductor pair, its sensitivity is reduced and the problem disappears.
One more thing: (Most important!), you won't hear interference FROM the oscillator in the lamp anymore on your radio.
And don't open up the module inside the lamp base, you are wasting your time there, and adding more work to glue the module back together.
Just Choke off the sense wire with the resistor and 2.5 mH choke. You'll be fine.
There will be one or more sockets for light bulbs - often all wired in parallel so that all the bulbs come on at the same time. For wall fixtures, there may be a switch on the fixture though most often the switch is mounted on the wall elsewhere.
Unlike table lamps where most of the heat rises from the bulb away from the socket, mounting the sockets horizontally or inverted (base up) can result in substantial heating and eventual deterioration of the socket and wiring. Common problems relate to this type of problem - bad connections or brittle wire insulation. Replacement parts are generally available at home centers and electrical supply houses. Just make sure to kill power before working on any fixture wired into your house's electrical system!
Then use a pair of needlenose pliers or any other tool that will grip what is left of the base to twist it free. A piece of a raw potato may even work!
Bulbs
Male o------O----O----O----O----O----O----O----O---+
Plug |
o---------------------------------------------+
Or the following which permits several strings to be connected end-to-end:
+---------------------------------------------+
| Bulbs |
Male o--+---O----O----O----O----O----O----O----O---+ +--o Female
Plug | Socket
o---------------------------------------------+-----o
Many variations on these are possible including multiple interleaved series strings. One of the bulbs in each circuit may be a flasher. All newer light sets must include a fuse as well.
In a series connected circuit, if one bulb burns out, all lights go out. The newer types include a device in each bulb which is supposed to mechanically short out that bulb if it burns out. However, these don't always work or you may have a set that doesn't have this feature.
The following assumes a single series circuit - large light sets (e.g., perhaps 50 or more) will have multiple series strings so you will have to identify the particular circuit that is bad. If more than one bulb is burnt out, this may further complicate matters.
To locate a burnt out bulb in a series string, you can use the binary search approach: pull a bulb in the middle of the string. Test the bulb and between the power cord end and the middle for low resistance. If these are ok, you know the bad bulb is in the other half. Then divide the 'bad' portion in half and test one half of it and so forth. For example, using this technique, you will need to make at most 6 sets of measurements to locate a bad bulb in a 50 light set.
Sears, K-Mart, Radio Shack, among others sell inexpensive testers (e.g., Lite-Tester Plus, about $4). These detect the electric field generated by the (now floating) wire on the Hot side of the gap of the burnt out filament. These will also locate open wires and blown fuses in the same manner.
I have also heard of bulb sets in which the individual bulbs are gas filled in such a way that if the filament breaks, current flows across the gap through the gas resulting in a faint glow in the burnt out bulb. I don't know if these things still exist.
WARNING: Do not be tempted to bypass a bad bulb with a wire. This will reduce the total resistance and increase the current to the remaining lamps shortening their life. Replace a few bulbs and the entire string will pop. This is a serious safety hazard especially on older light sets that may not have internal fuses. Also, some fuses look like lamps - replace only with an identical fuse - not with a lamp!
(From: Ken Bouchard (bouchard@ime.net).)
My advice, is trash them and go out and buy new ones. After all, you can get them typically around 5-10 bucks a set.
Then you have the old set to raid bulbs from, for the ones that blow out.
Quality control is not an issue when they build xmas lights. One slight tug of a wire, can break it, and the entire set goes dead.
First I assume you wiggled all the bulbs, often just a loose bulb causes this. In the smaller type bulb sets the string is wired in sections, so one bulb goes out, and every 4th or 5th one is dead.
The little bulbs were also designed, that if the filament breaks in the bulb a piece of foil inside it shorts out that bulb so that the remaining lights keep on working. This works up to a point, until more than 4-5 bulbs blow out at once, then the remaining ones get too much voltage and blow out too.
Often the cheesy sockets get water in them and corrode, and/or the wires on the bulb get twisted or broken.
They also use a cheap method of crimping the wiring together in these lights. Most times you can find the broken wire, by inspecting, seeing where it goes into the socket it pulls out easily.
Well avoid doing this when the set is live (heh...) unless you like the idea of getting zapped.
However, for the common type of tiny bulbs that are in series, you cannot really do this easily. Removing and bypassing 1 or 2 bulbs in a 50 light string won't have much effect on the remaining bulbs but cutting it in half will double the voltage on each bulb - you will get a very bright string of lights for a very short time.
The only way to shorten a string by more than a few percent of lights and have it survive is for the current to be limited by a bulb or resistor or to run it off of reduced voltage. A light dimmer might work except for the fact that they typically require a minimum load of 60 to 100 W - your light string is a small fraction of this.
However, for the special case of 1/2 (give or take) the original number of bulbs, there is a simple solution: A rectifier diode (1A, 200 V PRV min.) in series with the string will cut the effective voltage approximately in half. Typical part numbers are 1N4003 though 1N4007. Even Radio Shack will carry them.
Whatever you do, make sure your connections are secure (with wire nuts or properly soldered) and well insulated. For fire safety, the built-in fuse (usually at the plug-end) must be retained.
Should you care, these implement the multiple input XOR (exclusive OR) logic function for controlling electrical devices.
Note: See the section: Dimmer switches and light dimmers if you would like to have control of brightness of a lamp or fixture from multiple locations.
The descriptions below are for using traditional mechanical switches at more than one location. There are also electronic solutions, some even are wireless, where a control module is placed between the load (e.g., lamp or fixture) and the power line and the 'switches' or user controls are mounted remotely. The X10 system is a more general way of doing this providing fully programmable timed (automatic) switching and dimming (where appropriate) from one or more locations.
These are actually SPDT (Single Pole Double Throw) switches which look like ordinary wall switches but have 3 screws instead of 2. Two of these screws will be the same color (usually brass) while the third will be different (darker copper or brown). They may be marked as well.
Note that a socket for a 3-way bulb for a lamp is not related to this - only the name is similar.
Typical wiring for controlling a fixture or outlet from exactly two locations is as follows:
Location 1 Location 2
3-way SW A 3-way SW +---------+
/o----------------o\ | Fixture |
Hot o-----/ \o-----------| or |--------o Neutral
o----------------o Center | Outlet | Shell
B (brass) +---------+ (silver)
/o---o o---o
A 3-way switch connects either up o---/ or down o---o\ .
o---o \o---o
As usual, the brass screw on the fixture or outlet should be connected to the Hot side of the wiring and the silver screw to the Neutral side.
Another common variation is shown below:
Location 1 Location 2
3-way SW Rd : 3-way SW
: Bk /o------------------o\
Hot o-------------------------------/ Wh : \o---+
: o------------------o |
+---------+ : : |
| Fixture | : Wh Splice Bk : |
Neutral o-------| or |---------------X---------------------------+
| Outlet | : (Wirenut) :
+---------+ 14-2 14-3
Details may differ for your particular installation (like to which sides the Hot and Neutral are connected and/or particular wire colors used).
You may also see something along the lines of the following which works but may not be allowed by NEC Code for obvious safety reasons (the load can be electrically live even if off and someone wiring it this way may be tempted to pull the Hots and Neutrals from separate circuits) but has that ever stopped anyone from doing something stupid?):
+---------+
Hot o------------o\ | Fixture | /o------------o Hot
\---| or |---/
Neutral o------------o | Outlet | o------------o Neutral
+---------+
(And, if you accidentally get the Hots from opposite phases - watch out!)
4-way switches have 4 terminals arranged as two pairs. In one position pair 1 is connected to pair 2 straight through. In the other position, the connections are interchanged.
Typical wiring for controlling a fixture or outlet from 3 or more locations is as follows:
Location 1 Location 2 Location 3
3-way SW A 4-way SW A 3-way SW +---------+
/o------------o\ /o-----------o\ | Fixture |
Hot o---/ / \o---------| or |---o Neutral
o------------o/ \o-----------o Center | Outlet | Shell
B B (brass) +---------+ (silver)
o---o o\ /o
A 4-way switch connects either straight or exchange / .
o---o o/ \o
This can be extended to an arbitrary number of positions.
As usual, the brass screw on the fixture or outlet should be connected to the Hot side of the wiring and the silver screw to the Neutral side.
Note that a 4-way switch can be constructed from a DPDT (Double Pole Double Throw) type (e.g., toggle switch) as follows:
+--------------+
| |
A(in) o---------------+ |
| | |
+----o o/ o-------+------o A(out)
: | |
+----o o/ o---+----------o B(out)
| | DPDT |
B(in) o---------------+ toggle |
| switch |
+------------------+
For low voltage (non-house wiring) or panel mount applications, this may be easier than using actual 4-way switches (which are probably not available in small sizes).
The wires marked A and B (sometimes called 'travelers') may be in a single (Romex) cable and should be on the screws that are both the same color.
If you do use Romex with a black and white wire, put black tape on the insulation at the ends of the white wire (or paint the ends black) to indicate that this is a Hot wire and not a Neutral. This is required by Code but allows the use of this type of wire.
These diagrams represent one wiring arrangement. Sometimes, there are other slight variations. For example, you might find the switches in the Neutral instead of Hot portion of the wiring - however, this is not recommended.
Perhaps they got it right in the UK :-).
(From: Dion L Heap (Dion@homesix.globalnet.co.uk).)
I had to translate the American into the English. If anyone UK is reading this then for what we (UK) call 2 way lighting is the normal stairs light with 2 switches controlling it, (one up & one down). Both these switches are "2 way switches", to add another switch you would be creating 3 way lighting, for this you use both the existing 2 way switches and in-between the L1 & L2 you use an "intermediate switch" I asked at my supplier for a 4 way switch & they thought I was talking Japanese. A phone call to MK technical support revealed that the UK equivalent is the aforementioned intermediate switch. this has 4 points, the L1 & L2s from the 2 existing 2 way switches are taken through the intermediate.
So you forgot to label the wires before you removed the old switch, huh? :-).
Or, you moved the wires from the old switches to the new switches but guess what? The new switches may not have the corresponding screws in the same locations and your symptoms are that one switch has to be up for the other switch to do anything - and that is if you are lucky!
You have several options:
I won't even consider the case of more than 2 switches!
Or a slight variation on the theme:
(From: Greg Fretwell (JRFC31A@prodigy.com).)
"Pull out one of the switches (the first one you "fixed" to create this problem) mark all 3 wires. Rotate them all one terminal to the right. Try it. If no luck shift one more time. One of those should work."
Here is one way to identify the proper wires more quickly than trial and error but requires testing the live wiring:
Now, turn off the power and confirm that it is off by retesting the hot wire you identified above.
(From: CodeElectric@Worldnet.att.net).
Check both boxes. There will be a single Hot - that goes on the common of the 3-way switch. Put the other two wires on the other two screws.
Now, at the other switch, you will find one hot. Put that on a screw, not the common. Switch the other switch, and you'll find another hot. That is the other traveler. You've got one wire left,,, that's the other common.
In more detail:
Dimmers are available to replace standard wall switches and even for use in place of the light bulb socket/switch in most table lamps. However, nearly all of these are designed only for normal incandescent light bulbs - not fluorescents, compact fluorescents, or high intensity or halogen lamps (or any other type of lamp with a transformer).
(There are special dimmers for use with fluorescent lamps but these must be specifically matched to the lamp type and wattage and their dimming range is usually not very wide. See: the fluorescent lamp information at http://www.misty.com/~don/light.html for a discussion of dimming techniques and details on several relatively simple approaches that may work for your needs.)
Installation is generally very straightforward as there are only two wires and polarity does not matter. They simply replace the existing switch.
To assure long life, it is best to select a dimmer with a higher power rating than your maximum load. For example, if you are using four 100 W bulbs, a 600 W dimmer should be the minimum choice and one rated at 1000 W would be better. This is particularly true if halogen bulbs are used since these may be harder on dimmers than normal types. Further derating should be applied where multiple dimmers are installed in the same outlet box resulting in greater combined heating. Higher wattage dimmer switches will have better heat sinking as well which should result in the active components - the thyristors - running cooler. Dimmers are under the most stress and generate the most heat when operating at about 50% output.
Dimmers may fail due to power surges, excess load, momentary fault (short) at the instant of light bulb failure, or just plain old age. A failed dimmer will generally be stuck at full brightness since the thyristor will have shorted out. The mechanical on-off switch which is part of the dimmer will probably still work.
To more fully test it, you can make up a simple circuit with a wall plug and cord, and the dimmer in series with a 60-100 W light bulb (less wattage may not be enough to provide enough load and the dimming range may be restricted). Make sure everything is well insulatded!
For a 3-way type dimmer, test/connect between the common (different color wire ors crew) and each of the travelers (same color wires or screws) for all switch positions.
It is not generally worth worrying about repair of a dimmer as they are so inexpensive. However, before replacement confirm that there is no actual problem with the wiring (like a short circuit in the fixture) and that you are not overloading the dimmer.
While designed for incandescent or heating loads only, these will generally work to some extent with universal motors as well as fluorescent lamps down to about 30 to 50 percent brightness. Long term reliability is unknown for these non-supported applications.
CAUTION: Note that a dimmer should not be wired to control an outlet since it would be possible to plug a device into the outlet which might be incompatible with the dimmer resulting in a safety or fire hazard.
S1 is part of the control assembly which includes R1.
The rheostat, R1, varies the amount of resistance in the RC trigger circuit. The enables the firing angle of the triac to be adjusted throughout nearly the entire length of each half cycle of the power line AC waveform. When fired early in the cycle, the light is bright; when fired late in the cycle, the light is dimmed. Due to some unavoidable (at least for these cheap dimmers) interaction between the load and the line, there is some hysteresis with respect to the dimmest setting: It will be necessary to turn up the control a little beyond the point where it turns fully off to get the light to come back on again.
Black o--------------------------------+--------+
| |
| | |
R1 \ | |
185 K /<-+ |
\ v CW |
| __|__ TH1
| _\/\_ Q2008LT
+---|>| / | 600 V
| |<|--' |
C1 _|_ Diac |
.1 uF --- (part of |
S1 | TH1) |
Black o------/ ---------------------+-----------+
The parts that fail most often are the triac, TH1, or the combination
switch/control (S1/R1).
None of the simple 3-way dimmer controls permit totally independent dimming from multiple locations. With some, a dimmer can be installed at only one switch location. Fully electronic approaches (e.g., 'X10') using master programmers and addressable slave modules can be used to control the intensity of light fixtures or switch appliances on or off from anywhere in the house. See the section: True (electronic) 3-way (or more) dimmers.
However, for one simple, if inelegant, approach to independent dimming, see the section: Independent dimming from two locations - kludge #3251.
Note that the primary difference between this 3-way dimmer schematic and the normal dimmer schematic shown above is the addition of an SPDT switch - which is exactly what is in a regular 3-way wall switch. However, this dimmer also includes a choke (L1) and capacitor (C2) to suppress Radio Frequency Interference (RFI). Operation is otherwise identical to that of the simpler circuit.
This type of 3-way dimmer can be used at only one end of a multiple switch circuit. All the other switches should be conventional 3-way or 4-way types. Thus, control of brightness is possible only from one location. See the section: True (electronic) 3-way (or more) dimmers for reasons for this restriction and for more flexible approaches.
Red 1 o--------o
\
S1 o----+------------+-----------+
| | |
Red 2 o--------o | R1 \ ^ CW |
| 220 K /<-+ |
| \ | |
| | | |
| +--+ |
| | |
| R2 / |
C2 _|_ 47 K \ |
.047 uF --- / __|__ TH1
| | _\/\_ SC141B
| +---|>| / | 200 V
| | |<|--' |
| C1 _|_ D1 |
| .062 uF --- Diac |
| | |
| :::::: | |
Black o-----------------+---^^^^^^---+-----------+
L1
40 T #18, 2 layers
1/4" x 1" ferrite core
The parts that fail most often are the triac, TH1, or the combination
switch/control (S1/R1).
Whether this is really useful or not is another story. The wiring would be as follows:
Location 1 Location 2
3-way Dimmer A 3-way Dimmer +---------+
/o----------------------o\ | Lamp |
Hot o------o/ Silver 1 Silver 2 \o------| or |-----o Neutral
Brass o----------------------o Brass | Fixture |
Silver 2 B Silver 1 +---------+
(If dimming interacts, interchange the A and B wires to the silver screws at
one dimmer).
This one uses a toggle style potentiometer where the up and down positions operate the switches. Therefore, it has 3 states: Brass to Silver 1 (fully up), dim between Brass and Silver 1 (intermediate positions), and Brass to Silver 2 (fully down).
Br /o---o Br o---o Br/\/o---o
3-way dimmer is up o---o/ S1 or down o---o\ S1 or Dim o---o S1
o---o \o---o o---o
S2 S2 S2
However, it is still not possible to have totally independent control - local
behavior differs based on the setting of the remote dimmer (details left as
an exercise for the reader).
Like the previous circuit, this dimmer also includes a choke (L1) and capacitor (C3) to suppress Radio Frequency Interference (RFI). It is just a coincidence (or a matter of cost) that the 3-way dimmers have RFI filters and the 2-way type shown above does not.
Silver 1 o---+----------------+--------------------+-----------+
| | | |
| | R1 \ ^ Up |
| | 150 K /<-+ |
| | \ | |
| | | | |
| | +---------+--+ |
| | | | |
| C3 _|_ | R2 / |
| --- | 22 K \ |
| | | / __|__ TH1
| | C2 _|_ | _\/\_
| | .047 uF --- +---|>| / | 200 V
Up \ | | | |<|--' |
| | | C1 _|_ D1 |
| | |.047 uF --- Diac |
| | :::: | | |
| Dim o--------+---^^^^---+---------+-----------+
| / L1
Brass o---+---o 12T #18
1/4" x 1/2" ferrite core
Down o
|
Silver 2 o-----------+
The parts that fail most often are the triac, TH1, or the combination
switch/control (S1/S2/R1).
The simple type of 3-way dimmers are just a normal dimmer with a 3-way instead of normal switch. This allows dimming control from only one location. The other switches in the circuit must be conventional 3-way or 4-way type.
Connecting conventional dimmers in series - which is what such a hookup would require - will not really work properly. Only if one of the dimmers is set for full brightness, will the other provide full range control. Anywhere in between will result in strange behavior. The other dimmer may have a very limited range or it may even result in oscillations - periodic or chaotic variations in brightness. The safety and reliability of such an arrangement is also questionable.
True 3 way dimmers do exist but use a more sophisticated implementation than just a normal dimmer and 3-way switch since this will not work with electronic control of lamp brightness. One approach is to have encoder knobs (similar to those in a PC mouse) or up/down buttons at each location which send pulses and direction info back to a central controller. All actions are then relative to the current brightness. A low cost microcontroller or custom IC could easily interface to a number, say up to 8 (a nice round number) - of control positions. The manufacturing costs of such a system are quite low but due to its specialty nature, expect that your cost will be substantially higher than for an equivalent non-dimmable installation.
If control of intensity at only one of the locations is acceptable, a regular dimmer can be put in series with the common of one of the normal 3-way switches. However, your brightness will be set by that dimmer alone. See the section: Typical dimmer schematics.
An alternative is to use X-10 technology to implement this sort of capability. This would likely be more expensive than a dedicated multi-way switch control but is more flexible as well. X-10 transmits control information over the AC lines to select and adjust multiple addressable devices like lamps and appliances.
However, for the adventurous, see the section: Independent dimming from two locations - kludge #3251.
Location 1 Location 2
+--------+ 4-way SW 3-way SW
Hot o--+---| Dimmer |----o\ /o--------o\ +---------+
| +--------+ / \o----------| Fixture |------o Neutral
| +--o/ \o--------o Center +---------+ Shell
| | (brass) (silver)
| | +--------+
| +------------| Dimmer |--+
| +--------+ |
+---------------------------------------+
As usual, the brass screw on the fixture or outlet should be connected to the
Hot side of the wiring and the silver screw to the Neutral side.
The dimmers can be any normal knob or slide type with an off position.
Note that as drawn, you need 4 wires between switch/dimmer locations. 4-way switches are basically interchange devices - the connections are either an X as shown or straight across. While not as common as 3-way switches, they are available in your favorite decorator colors.
If using Romex type cable in between the two locations, make sure to tape or paint the ends of the white wires black to indicate that they may be Hot as required by Code.
And, yes, such a scheme will meet Code if constructed using proper wiring techniques.
No, I will not extend this to more than 2 locations!
Also see the section: Controlling a fixture or outlet from multiple locations.
CAUTION: However, note that a dimmer should not be wired to control an outlet since it would be possible to plug a device into the outlet which might be incompatible with the dimmer resulting in a safety or fire hazard.
The severity of the problem is due to a variety of causes with the two most likely being related to the bulb's filament construction/supports and what, if any filtering, is provided by the dimmer itself - some are just worse than others and cost may not be a reliable indication of which-is-which.
There is nothing really wrong with your installation - incorrect wiring would result in it not working at all, blowing a fuse or tripping a breaker, or or not working in certain positions of switches in a 3-way or 4-way (multiple switch locations) setup. If it bothers you try a different brand of bulbs or a different brand of dimmer.
Touch dimmers work in a couple of different ways, depending on the IC used. Simple ones, such as those in the cheap 'touch lamps' that you find for sale on market stalls, etc. normally have three or four preset brightness levels and an OFF setting, which are operated sequentially: touch once for full brightness, again to dim slightly, again to dim a bit more, etc, until the OFF setting is reached. The next touch will then bring the lamp to full brightness.
The better (and more expensive) units, such as the touch dimmer switches that are sold as direct replacements for conventional light switches, are similar, but have many more steps. A single touch will usually bring the lamp to full brightness, while keeping your finger in contact with the touch plate will slowly dim the lamp. You just remove your finger when the lamp is at the required brightness level.
Both kinds of touch dimmer have three basic parts;
There are a number of specially designed IC's available for touch dimmers, notably the HT7704B ,a four-step device for touch lamps as described above, and the SLB0586A, which is the other kind, with facilities for remote control.
(From: Jack Schidt (jack@wintel.net).)
Body detection usually follows one of three forms:
(Zero crossing switching, a technique used with electrical heaters and heating appliances to minimize RFI cannot be used for lighting as it would result in way too much flicker or a very limited number of brightness levels.)
Better light dimmers will include a bypass capacitor (e.g., .01 uF, 1kV) and a series inductor to suppress RFI but these components were often left off in basic models. The FCC has tightened up on their regulations around 1992 so replacing older dimmer switches with newer ones may be the easiest solution.
I can't really recommend a particular model that it better in this regard. However, the package may list 'low RFI' as a feature so checking out Home Depot or wherever won't hurt.
Installing in-line power line filters may work but other options like replacing all your house wiring with metal conduit, or only listening to FM radio are probably not realistic!
BTW, I have used dimmers and AM radios to trace wiring inside the wall! :)
My recommendation would be to get a dimmer rated for 30 to 50 percent more power than you are using. It will still get warm but will have a better (probably finned) heat sink and will be running way below it maximum rating and should be more reliable. In general, any device should be derated to boost longevity!
It is very tempting to try using a common light dimmer to control devices using power transformers. Will this work?
It will usually work fine, but it can lead to a fire hazard and is not recommended. Most major dimmer manufacturers have special dimmers designed for this application, that prevent the hazard inherent in using a standard dimmer. It is worth your while to use one of those.
The problem results from the inductive nature of the impedance the transformer presents to the dimmer. The load is most inductive when the transformer is lightly loaded. Even if you set up your system with a fully loaded transformer, it can become lightly loaded when bulbs burn out. If there is any small asymmetry in the firing angle of the triac on the two half cycles, there will a be small DC voltage across the transformer winding. This is no big deal - you'll get a bit of DC current, and the core will run with some DC flux, and may saturate a bit, but neither will cause significant heating or a real hazard. However, the point at which the triac turns *off* will also then be different on the two half cycles. Because ordinary dimmer circuits time the triac turn on from the turn off point, not from the line voltage zero crossing, the asymmetry in turn-off times leads to a even greater turn-on time asymmetry. If the load is sufficiently inductive, this process can "run away" until the dimmer is acting as a diode, applying nearly full line voltage across the transformer winding. Ordinarily, this would result in enough current to trip a circuit breaker or a fuse, but smaller transformers can have enough DC resistance to keep the current low enough that the breaker does not trip. When I've experimented with this, the transformer winding soon started to smoke. I didn't continue the experiments to see what would happen next, but there have been reports of fires starting this way. A suitably rated small fuse installed in series with the transformer would probably work but I wouldn't want to depend on it.
Dimmers designed for this application can use several methods to get around the problem. Some use a DC detection circuit and shut off if DC is detected. Others use a three-wire connection scheme, such that the line- neutral voltage is available to the dimmer, and can be used for the timing reference, so that the triac is always fired at the same time relative to the line-voltage zero crossing, not relative to when the triac turns off. Thus, although there may still be a small amount of DC present due to asymmetry in the firing circuit, the system can never run away to the point of applying a much high DC voltage. (In good dimmers designed for this application, the asymmetry will also be small to begin with.)
References for further information:
But there is one type of failure to which virtually all dimmers may succumb caused not by a problem in the dimmer but by a transient event when an incandescent lamp burns out. When such a lamp reaches end-of-life, the filament opens and an arc forms which can expand to essentially result in close to a short circuit across the lamp. This happens within a very short time, perhaps one cycle of the AC. At that instant, a very high current flows likely blowing the triac in the dimmer. The result is that the dimmer now is stuck at full brightness (or off, if the switch is still functional).
Why isn't there a fuse? Actually, larger incandescent lamps do have fuses in their base, and these fuses may blow when the lamp burns out. But not fast enough to save the triac. Since dimmer switches are not designed to be repairable - they are considered disposable devices - the cost of including a fuse cannot be justified even if a fuse would work.
The triac may also fail if the dimmer is used in an attempt to control something other than an incandescent lamp, or least, something other than a resistive load. Using a normal light dimmer to control the speed of a motor is a hit or miss affair, and may result in damage to both the dimmer and motor depending on type.
The most common problem after dead batteries is very often damage due to leaky batteries. Even supposedly leak-proof batteries can leak. Batteries also tend to be prone to leaking if they are weak or dead. Therefore, it is always a good idea to remove batteries from any device if it is not to be used for a while. How to assure the batteries will be with the flashlight? Put them in separate plastic bags closed and fastened with a twist tie.
Test the batteries with a multimeter - fresh Alkalines should measure 1.5 V. Any cell that measures less than about 1.2 V or so should be replaced as they will let you down in the end. On a battery tester, they should read well into the green region.
Check the bulb with a multimeter on the ohms scale - a bad bulb will test open. Bulbs may fail from use just like any other incandescent lamp or from a mechanical shock - particularly when lit and hot. Replacement bulbs must be exactly matched to the number and type of batteries (cells). A type number is usually stamped on the bulb itself. There are special halogen flashlight bulbs as well - I do not really know how much benefit they provide.
The switches on cheap flashlights are, well, cheaply made and prone to unreliable operation or total failure. Sometimes, bending the moving metal strip a bit so it makes better contact will help.
Clean the various contacts with fine sandpaper or a nail file.
If a flashlight has been damaged as a result of battery leakage, repair may be virtually impossible.
High quality flashlights are another matter. Maglights(tm) and similar units with machined casings and proper switches should last a long time but the same comments apply to batteries - store them separately to avoid the possibility of damage from leakage. Keep a spare bulb with each of these - the specialty bulbs may be harder to find than those for common garbage - sorry - flashlights.
Rechargeable flashlights include a NiCd or lead-acid battery (one or more cells in series) and the recharging circuitry either as part of the unit itself or as a plug-in wall adapter or charging stand. See the sections: "Battery chargers" and "Typical rechargeable flashlight schematics" for more information.
It is a really simple, basic charger. However, after first tracing out the circuit, I figured only the engineers at First Alert knew what all the diodes were for - or maybe not :-). But after some reflection and rearrangement of diodes, it all makes much more sense: C1 limits the current from the AC line to the bridge rectifier formed by D1 to D4. The diode string, D5 to D8 (in conjunction with D9) form a poor-man's zener to limit voltage across BT1 to just over 2 V.
The Series 50 uses a sealed lead-acid battery that looks like a multi-cell pack but probably is just a funny shaped single cell since its terminal voltage is only 2 V.
Another model from First Alert, the Series 15 uses a very similar charging circuit with a Gates Cyclon sealed lead-acid single cell battery, 2 V, 2.5 A-h, about the size of a normal Alkaline D-cell.
WARNING: Like many of these inexpensive rechargeable devices with built-in charging circuitry, there is NO line isolation. Therefore, all current carrying parts of the circuit must be insulated from the user - don't go opening up the case while it is plugged in!
2V LB1 Light
1.2A +--+ Bulb S1
+--------|/\|----------o/ o----+
_ F1 R3 D3 | +--+ |
AC o----- _----/\/\---+----|>|--+---|----------------------+ |
Thermal 15 | D2 | | 4A-h | |
Fuse | +--|>|--+ | BT1 - |+ 2V | |
| | D4 +--------------||------|-------+
+----|<|--+ | | | |
| D1 | | D8 D7 D6 D5 | D9 |
+--------+-------+--|<|--+---+--|<|--|<|--|<|--|<|--+--|>|--+
| | |
| / |
_|_ C1 \ R1 |
--- 2.2uf / 100K |
| 250V \ |
| | R2 L1 LED |
AC o---+--------+--------------/\/\-----------|<|------------------+
39K 1W Charging
S1
11.2 VRMS +---------------o/ o----+
AC o-----+ T1 R1 LED1 D1 | +| | | - |
)|| +----/\/\-----|>|---->>----|>|----+---||||||---+ |
)||( 33 Charging 1N4002 | | | | KPR139 |
)||( 2W BT1 | LB1 |
)||( 3.6V, 1 A-h | +--+ |
)|| +-------------------->>------------------------+----|/\|--+
AC o-----+ Light Bulb +--+
|<------- Charger ---------->|<---------- Flashlight ----------->|
I could not open the transformer without dynamite but I made measurements of
open circuit voltage and short circuit current to determine the value of R1.
I assume that R1 is actually at least in part the effective series resistance
of the transformer itself.
Similar circuits are found in all sorts of inexpensive rechargeable devices. These have no brains so they trickle charge continuously. Aside from wasting energy, this may not be good for the longevity of some types of batteries (but that is another can of worms).
There is an added wrinkle which provides a blinking light option in addition to the usual steady beam. This will also activate automatically should there be a power failure while the unit is charging if the switch is in the 'blink' position.
With S1 in the blink position, a simple transistor oscillator pulses the light with the blink rate of about 1 Hz determined by C2 and R5. Current through R6 keeps the light off if the unit is plugged into a live outlet. (Q1 and Q2 are equivalent to ECG159 and ECG123AP respectively.)
R1 D1 R3 LED1
AC o---/\/\----+----|>|-------+---+---/\/\--|>|--+ D1-D5: 1N4002
33 ~| D2 |+ | 150 |
1/2W +----|<|----+ | | R4 | D5
D3 | | +------/\/\----+--|>|--+
C1 +----|>|----|--+ | 33, 1/2W | LB1 2.4V
1.6uF ~| D4 | | | | | +--+ .5A
AC o--+---||---+----|<|----+--+---|--||||--------------+-+---|/\|----+
| 250V | |- | - | |+ | +--+ |
+--/\/\--+ | | BT1 + C2 - | R5 |
R2 | | 2.4V +---|(----|-----/\/\----+
330K | | | 22uF | 10K |
| | R6 | |/ E |
| +---/\/\---+-+-----| Q1 |
| 15K | |\ C +---------+
| / C327 | | |
| R7 \ PNP | | 1702N |
| 100K / | | NPN |/ C
| \ +---|-------| Q2
| On | | |\ E
| S1 o---------|-----------+ |
+----o->o Off | |
o---------+---------------------+
Blink/Power Fail
+------+---|>|---+------------+----------+
| | D1 | | |
| | 1N4004 | / |
| | | \ R3 __|__
+| SC1 | +_|_ BT1 / 2.2K _\_/_ LED
+--+--+ | _ 2xAA NiCd \ |
|Solar| | ___ 550mA-hr | |/ C
|Cell | | - _ +---+----| Q2 SS8050
+--+--+ | | R2 | | |\ E (ECG216)
-| | | 20K |/ C / |
| +---------|---/\/\---| Q1 \ R1 |
| | SS9013 |\ E / 100K |
| | (ECG123A) | | |
+----------------+------------+---+------+
When there is enough voltage from the solar cell, Q1 is turned on and Q2
(the LED driver) is turned off. As far as I can tell, there is nothing to
actually limit current to the LED except for the combination of battery,
transistors, LED, and wiring resistance. Both transistors could probably
be replaced with 2N3904s. So, if you were duplicating this thing, I'd
recommend adding something to control the current to the LED or at least
checking it first!
Actual failure of this complex device would most likely be due to worn out NiCd cells or corrosion to due exposure to the weather.
Operational problems like weak output or inadequate lighting time could be due to insufficient Sunlight (the thing is installed under a bush!) or extended cloudy conditions. Of course, these don't produce a huge amount of light in any case!
Replacing incandescent light bulbs can usually be done without disassembly. The bulbs may be of the specialty variety and expensive, however.
When a unit using fluorescent bulbs will no longer come on, the most likely cause is a bad bulb. However, replacement may involve disassembly to fain access. Where two bulbs are used, either one or both might be bad. Sometimes it will be obvious which is bad - one or both ends might be blackened. If this is not the case, replacement or substitution is the only sure test. These **will** be expensive $7-10 is not uncommon for an 8 inch fluorescent bulb!
Other possible problems: plug, cord, switch, light bulb sockets.
If none of the lights come on, check for a blown fuse or circuit breaker, bad wall switch or dimmer, a bad connection in the ceiling box or elsewhere in the house wiring, or a bad connection where the cord is joined to the individual socket wires.
Where only one bulb does not light - and it is not a burned out bulb - a bad socket, loose wire connection at the socket, or bad connection at the point where the wires are joined (Wire Nuts(tm) or crimps) is likely.
A basic projector consists of a really bright lamp - usually halogen but some fancy ones use a High Intensity Discharge (HID) lamp (see the document: Gas Discharge Lamps, Ballasts, and Fixtures), a cooling fan, electrical and thermal protection devices, and possibly an interlock switch to prevent operation with the cover removed. The main switch may include reduced brightness settings which adds some resistance or a diode in series with the lamp.
(Repair of those with HID lamps unless it is a simple bad connection or failure in the protection devices is well beyond the scope of this document unless replacing the lamp is all that is needed. WARNING: The types of power supplies used for these may have capacitors that can retain a dangerous charge for a long time even after the plug is pulled.)
A reflector and condensing lens concentrates the light more or less uniformly onto the material to be projected {transparency or whatever) and a projection lens relays and enlarges that to the screen. Note that the large Fresnel lens (which should also be cleaned) that usually serves as the transparency platform of an overhead projector is not the primary condenser but serves a similar function directing most of the light which passes through the transparency to the projection lens. There may also be one or more pieces of heat absorbing glass between the lamp and condenser. While you're in there, a careful cleaning of the optics could be useful! After making sure the unit is unplugged, use a cloth moistened with isopropyl alcohol to clean all accessible optical surfaces. Rubbing (70%) or medicinal (91%) alcohol is fine as long as it doesn't contain any additives. Be gentle - optical glass is not that hard! WARNING: Avoid contact with the glass envelope of the lamp itself. If you do touch it by accident, use a fresh cloth or paper towel and alcohol to remove all traces of skin oils since this contamination can lead to failure at the elevated temperatures at which these run.
Like all incandescent lamps, those in projectors burn out - and since they are run at higher than normal wattage to get the most and whitest light, they usually are only rated for a small number of hours (e.g., 100). When burnout occurs, other components may be blown as well.
Since everything runs hot, deteriorated connections, contacts, sockets, etc., are quite common. Any major damage will require repair or replacement of the offending components. The fan may be on a thermostat which can also fail. If the fan doesn't start (usually immediately or after a minute or so at most), overheating WILL occur. Check the thermostat (bypass it to test) and the fan for dry bearings, bad connections, or a bad motor.
If replacing the bulb doesn't help, check the fuses and thermal protectors for opens. Check the outlet as the burnout may have blown the fuse or tripped the circuit breaker for that branch circuit.
If the new bulb runs excessively bright, TURN IT OFF IMMEDIATELY! Some of these projectors use 82 V bulbs (it will say on the bulb and/or its package), and a series diode (or diodes) may be used to reduce power to the bulb to run it at an effective voltage of 82 VRMS. (The RMS value of half wave rectified 115 VAC is close to 82 V). When the old bulb blew (or even if it didn't), these diodes can fail - often shorted. The new bulb won't last long on the full line voltage. The replacement diodes need to have a PIV rating of at least 200 V (for 115 VAC power) and a current rating adequate to handle the operating current and the initial surge (which can be 10X of that). Depending on the bulb's wattage, a 25 A or higher diode may be needed. An proper replacement will be available from the projector manufacturer but will be more expensive than one purchased from an electronics distributor.
There are two kinds of problems: totally dead or stuck/sluggish.
A totally dead fan can be the result of several possible causes:
Sluggish operation can be due to gummed up lubrication in the motor or any gears associated with an automatic oscillating mechanism. Disassemble, thoroughly clean, and then lubricate the motor bearings with electric motor oil. Use light grease for the gearbox but this is rarely a problem.
A noisy fan may be due to dry motor or other bearings or loose hardware or sheetmetal. Disassemble, clean, and lubricate the motor or gearbox as above. Inspect for loose covers or other vibrating parts - tighten screws and/or wedge bits of wood or plastic into strategic locations to quiet them down.
Damaged fan blades will result in excessive vibration and noise. These may be easily replaceable. They will be attached to the motor shaft with either a large plastic 'nut' or a setscrew. However, locating a suitable set of blades may be difficult as many cheap fans are not made by well known companies.
Ball bearing fans rarely fail for mechanical reasons but if the bearings become hard to turn or seize up, replacement will usually be needed. (Yes, I have disassembled ball bearings to clean and relube THEM but this used only as a last resort.)
WARNING: For power supply fans, be aware that high voltages exist inside the power supply case for some time (perhaps hours) after the unit is unplugged. Take care around the BIG capacitors. If in doubt about your abilities, leave it to a professional or replace the entire power supply!
The only type of repair that makes sense is cleaning and lubrication. Else, just replace the fan or power supply. It isn't worth troubleshooting electronic problems in a fan!
If you want to try to clean and lubricate the bearings, the blade assembly needs to be removed from the shaft. There should be a little clip or split washer holding it on. This is located under a sticker or plastic plug on the center of the rotating blade hub. Once this fastener has been removed, the blades will slide off (don't lose the various tiny spacers and washers!)
Thoroughly clean the shaft and inside the bushings and then add just a couple drops of light oil. Also, add a few drops of oil to any felt washers that may be present as an oil reservoir.
Reassemble in reverse order making sure the tiny washers and spacer go back in the proper positions.
How long this lasts is a crap shoot. It could be minutes or years.
Replacement fans are readily available - even Radio Shack may have one that is suitable. Nearly all run on 12 VDC but some small CPU fans may use 5 VDC. While current ratings may vary, this is rarely an issue as the power supply has excess capacity. Air flow rates may also vary depending on model but are usually adequate for use in PCs.
Advantages include virtually infinite life, very low power consumption, to nearly total silence when operating. However, they aren't going to cool very much :-).
(If you care, something that is said to be piezo electric changes shape (e.g., bends or compresses/expands) when a voltage is applied (and vice-versa). Many materials exhibit the piezo electric effect include crystals like quartz, various ceramics and plastics, and even some organic compounds. The most common example of a piezo electric device in modern technology is the beeper in a common digital watch, pocket alarm clock, or pager - in which case an electrical signal at a most annoying frequency causes the change in thickness of a ceramic disk and results in the audible tone.)
The piezo fan I have is just a pair of thin plastic flaps or vanes, each about 1/2" x 3", separated by perhaps 1" and slightly diverging. A pair of piezo elements at one end vibrate the vanes when driven through a dropping resistor from the 60 Hz AC line. Interestingly, the resonance is actually at 50 Hz but I do not think this unit was designed for European power. A plastic housing helps to guide the air flow - what of it there is. The result is a just detectable breeze so I wouldn't recommend using one of these to cool your Pentium II!
Except for mechanical damage, there isn't much to go wrong as long as the piezo elements themselves are getting power. However, a buildup of dirt on the vanes could change the resonant frequency to the point of greatly reducing effectiveness (to the extent that there is any to begin with!).
Don't worry, you may never see one of these things in several lifetimes :-).
Usually, the answer is a qualified 'yes'. Except for some that are internally regulated or thermostatically controlled, the speed is affected by input voltage. It is likely that the fan will run on anywhere from .5 to 1.25 times the nominal input voltage though starting when it is near the low end of this range may need some assistance.
A universal DC wall adapter, adjustable voltage regulator, or (variable) series power resistor can provide this control. For example:
25, 2 W + +--------+ -
+12 VDC o-----+---/\/\---+--------| DC FAN |----o Gnd
| + | +--------+
+----|(----+ 12 VDC, .25 A
10,000 uF
25 V
The 25 ohms power resistor should reduce the speed of this fan by about 25 to
30 percent. The capacitor provides full voltage for a fraction of a second to
assure reliable starting.
These small shaded pole fans will work just fine on a Variac. Any speed you want, no overheating, etc. I had done this with all sorts of little computer cooling fans as well as larger ones (remember those old DEC PDP-11 rack fans?).
A true rheostat (variable power resistor) will also work. However, significant power will be dissipated in the rheostat which must be sized so that the maximum power density of any portion of its element does not exceed its power handling capability - this can end up resulting in a massive device even for a small fan. For example, to vary a 120 VAC fan rated at 24 VA from between 1/2 to full power would require a 600 ohm, 25W rheostat; down to 1/4 power would require an 1,800 ohm 75 W rheostat!
Small triac based speed controls like those used for ceiling fans may also work. Even light dimmers will *probably* work for medium size fans or banks of fans though I cannot guarantee the reliability or safety of these. The problem is that small induction motors represent a highly inductive loads for the light dimmer circuitry which is designed for a resistive load. I have achieved a full range of speeds but over only about 1/4 to 1/2 of the rotation of the control knob. There is some buzz or hum due to the chopped waveform.
However, from my experiments, light dimmers may have problems driving a single small fan. If the load is too small, the result may be a peak in speed (but still way less than normal) at an intermediate position and the speed actually much lower when on full, or reduced speed even on full. In this case, adding a resistive load in parallel with the motor - a light bulb for example - may improve its range. It adds a sort of quaint look as well! :-)
If you do opt for a solid state speed control, make sure you include a fuse in the circuit. A partial failure of the triac can put DC through the motor which would result in a melt-down, lots of smoke, or worse. (This isn't a problem with a light bulb load since its resistance is the same for AC and DC; a motor's DC resistance is quite low.)
The reason these simple approaches will work for these AC motors is that they are high slip to begin with and will therefore have a high range of speed vs. input voltage. The only concern is overheating at some range of lower speeds due to reduced air flow. However, since these fans are normally protected even against stall conditions, I wouldn't expect overheating to be a problem - but confirm this before putting such fans into continuous service.
If all you need to do is provide a fixed, reduced speed for a bank of similar AC fans, try rewiring them as two sets of parallel connected fans in series. The result will be 1/2 the normal line voltage on each fan motor which may provide exactly the speed you want! The extension to more than 2 sets of fans is left as an exercise for the student :-).
A ceiling fan is just an induction motor driving a set of blades. Multiple taps on the motor windings in conjuac dansnction with a selector switch provides speed control for most inexpensive fans. Better units include a solid state motor speed control.
The light often included with the fan unit is usually just an incandescent fixture with 1-5 bulbs and a switch. This may be a simple on-off type, a selector to turn on various combinations of bulbs, or a dimmer with continuous or discrete control of illumination.
WARNING: Always check mechanical integrity of fan mounting when installing or servicing a ceiling fan. Original design and construction is not always as fail-safe as one might assume. Double check for loose nuts or other hardware, adequate number of threads holding fan to mounting, etc. These have fallen without warning. Only mount in ceiling boxes firmly anchored to joists - not just hanging from the ceiling drywall! Check that the fan is tight periodically. The constant vibration when running, slight as it is, can gradually loosen the mounting hardware. Furthermore, if pull chain type switches are used for the fan or light, constant tugging can also tend to loosen the entire fan.
Failures of ceiling fans can be divided into electrical and mechanical:
Electrical:
For an existing installation that suddenly stopped working, a bad cap is a likely possibility. An induction motor that will not start but will run once started by hand usually indicates a loss of power to the starting (phase) winding which could be an open or reduced value capacitor.
This is probably a capacitor-run type of motor where the capacitor provides additional torque while running as well. Therefore, even starting it by hand with the blades attached might not work. With the blades removed, it would probably continue to run. Of course, this isn't terribly useful!
I use synthetic transmission lube, 80-130 (manual gearbox, not automatic transmission fluid which is very thin --- sam). I imagine that any similar lubricant, synthetic or not, would work as well, but the synthetic flows down in better and works well.
Do not use WD-40, 3-in-1 oil or any other lightweight oil. Motor oil is good as well, but it does not stick to the bearings as well. DO NOT use automatic transmission fluid - extremely thin.
Grease would be perfect, white lithium, divine! But, getting the grease down into the bearings would be very difficult.
Just about three or four drops should be all it takes. Getting it on the lower bearings of the ceiling fan will be tough. I have an oil can that I pump a drop to the tip of, then hold it against the bearings until they wick the oil inside. This is very slow. It takes about 15 minutes per fan to oil, clean the top of the blades, oil a little around the hanging ball, pull the globe off and clean the globe inside, and make sure everything is OK.
Doing this will likely result in a nasty hum or buzz at anything other than full brightness (speed) or off. This is both annoying and probably not good for the fan motor as well. A dimmer works by reducing the power to the light by controlling when the voltage is applied on each cycle of the AC. If it is turned on half way through the cycle half the power is provided, for example. However, with cheap lamp dimmers, this results in sharp edges on the waveform rather as peak voltage is applied suddenly rather than with the nice smooth sinusoid. It is these sharp edges causing the coils or other parts of the fan to vibrate at 120 Hz that you are hearing.
Special speed controls designed for ceiling fans are available - check your local home center or ceiling fan supplier.
Here is another alternative:
(From: Rick & Andrea Lang (rglang@radix.net).)
Here's a potential solution if you don't mind spending a little more for a ceiling fan (If you already have one in that location, perhaps you can put it in another room). Ceiling fans with remote control are now available. They only require power to the ceiling fan (2 wire) and a remote control. With the remote you can dim the lights, slow the fan or both. You can then use the existing new wall switch as a power ON/OFF switch also. If you choose this route, be careful of interference with garage door openers. Usually, the remotes have at least 4 frequency selections to help avoid interference with other remote systems. I put one in that three of the four frequencies opened the garage door. I lucked out on the 4th one!
(From: David Buxton (David.Buxton@tek.com).)
A quickie test. Get the fan turning at a speed that demonstrates the throbbing noise. Come up with a way to instantly remove power to the fan. If the noise continues for a little bit until the fan has slowed down enough, then you know the noise is in the mechanical dynamics, perhaps blades out of balance. If the noise quits instantly with power removal, then you need a better speed control better designed for fan motor control.
Ceiling fans are normally multipole, capacitor-run types. They normally run fairly close to stalled, the blades being big enough that the motor never gets anywhere near synchronous speed.
Speed control in three speed types is by switching the value of the cap in series with the quadrature windings. The caps normally have two sections of 3 and 6 uF, with a common connection between the two sections allowing connections of 3, 6, or 9 (3 in parallel with 6) uF total.
I have seen some caps of slightly different value, but they should be close, just translate my 3 and 6 to what you actually have in what follows.
The higher the capacitance the higher the stall torque, so the faster the fan runs against the non-linear (square-law) torque vs. speed characteristic of the blades. (remember I said it is always pretty much stalled)
If you miswired the cap, then you may be getting 3 or 6 and 2 (3 in *series* with 6 uF which would result in low speeds. This *is* the case if any 2 out of 3 speeds seem to be the same. The replacement caps are usually marked with what terminal is which, but originals often are not. I don't know if there is a standard color code, but manufacturers are under no obligation to adhere to it even if there was. If you are totally lost, there are only 6 possible ways to connect the capacitor. 2 of these will give you all 3 speeds (but one in wrong order). So if you keep good notes (essential here) then you could try all possibilities in 20 minutes or so...yes, you're probably working with hands over head, what you wanted easy too?
OK, here is how to get it in 3 tries max:
Identify the "common" capacitor lead (connects to both 3, and 6 uF sections, hopefully your replacement is marked). It is currently connected to the wrong place, so swap it with one of the other cap wires. If you now have three speeds in the correct order, then your done. If you have three speeds in the wrong order, then leave common wire alone, but swap other two. (correct order is: off-hi-med-lo usually)
If you *didn't* have three different speeds following the first wire swap, then swap that common wire with the one wire you haven't moved yet. Now you should have three speeds, now correct the order as described, if needed.
If you currently have three speeds, but all are too slow, then it is likely that your fan needed a higher value capacitor. another explanation might be that the old cap was getting leaky when it warmed up after start, and letting the fan have extra current, thus giving extra speed.
In my experience, the three speed types should run from just slow enough to follow with the eye, to fast, fairly noisy, and making a fair amount of wobble on the mounting.
Continuously variable speed types put a fixed 9 or 10 uF cap in series with the quadrature winding, and regulate voltage to both windings via lamp-dimmer style triac circuit.
Depending on what wiring you have and what new wiring needs to be installed, I would install 14/3 cables for all ceiling lights. That way, you will be able to control ceiling fan and light from two separate switches.
Each time a new light has to be installed in our house, I make sure a 14/3 wire is installed. For three-way switches, I make it two 14/3 wires, even if I don't install a ceiling fan now. A 14/3 wire is not that much more expensive, and 10 years down the road, it might be useful.
The local high-end lights-and-fans shops have a handout that recommends that wherever a ceiling fan is to go have the following wiring:
The handout sheet also point out that adding a extra brace to the ceiling during any remodeling or new construction sized for a 100 pound dead weight is a good idea - it can be as simple as a couple of feet of 2x6" lumber and a couple of sheet metal fasteners. A wobbling fan can cause fatigue in a light duty metal brace rapidly. The extra cost is minimal, and it can prevent a fan from landing in the middle of the bed!
(From: George Eccles (geccles@ibm.net).)
I just took ceiling fan motor apart. The (center) stator has 16 coils, in 2 concentric groups of 8, arranged around the circumference of a flat disk. The groups are offset from each other by (maybe) 20 or 30 degrees. Based on resistance readings, I think one group is all wired in series. (I think) the other group is arranged in different combinations, based on the speed setting. For highest speed, I think all are in series, though I don't know what the phasing is. For the lower speeds, 1 or 2 coil pairs have their phasing reversed.
The rotor (aka the housing) has no visible windings, and no permanent magnets. AFAIK, it's just a thin ring (maybe 1/2" thick vertically, 3/4" radially) of laminated (maybe 10 or 12) strips of ferrous metal, embedded in a slightly larger aluminum casing. The laminations are not insulated from each other. Along the innner cicumference, the laminations are interrupted with weird pattern of what might be just interlocking to the aluminum casing.
Electronic air cleaners include a high voltage low current power supply and oppositely charged grids in the air flow. A failure of the solid state high voltage generator can result in the unit blowing air but not removing dust and particulate matter as it should. A typical unit might have 7.5 to 10 kV at 100 uA maximum (short circuit current, probably less at full voltage). Actual current used is negligible under normal conditions. This voltage is significant but the current would be just barely detectable, if at all.
The power supplies for smaller table top devices like the AirEase(tm) Personal Space Ionization Air Cleaner from Ion Systems, Inc. would probably generate similar voltages (possibly slightly lower) but at much lower current - perhaps only, 5 to 10 uA.
The modules are usually quite simple: a transistor or other type of switching circuit driving a step-up transformer and possibly a diode-capacitor voltage multiplier. See the sections: "Electronic air cleaner high voltage module schematic" and "Auto air purifier schematic" for an example of a typical circuit.
Where there is no high voltage from such a device, check the following:
On the topic of high voltage power supplies/transformers:
(From: Marvin Moss (mmoss@mindspring.com).)
These transformers have a very large air gap in the core and are designed to be able to operate for an extended period of time when the output is short circuited. If you get a piece of dirt or aluminum foil or something conductive in the filter, it has to bear the short until you clean the filter. I found several sources of surplus high voltage power supplies in the range of 5,000 volts at 2 mA. or so for $14.95 and bought several of them. I did in fact replace one of my two supplies in my A/Cs with this unit and it has been working perfectly for about 10 years now. The voltage is not critical but too high a voltage will create excessive ozone. Too low a voltage will not filter well. I think that 3,500 to 6,000 volts is the range but I can give you more info if you want it.
This module produces both positive and negative outputs when connected to 115 VAC, 60 Hz line voltage. Each is about 5 kV at up to around 5 uA.
The AC line powered driver and HV multiplier are shown in the two diagrams, below:
D1 T1 o
H o--------------|>|----+---+--------------------+ +-----o A
1N4007 | | Sidac __|__ SCR1 ::(
| | R3 D2 100 V _\_/_ T106B2 ::(
AC C1 | +--/\/\---|>| / | 200 V ::(
Line Power .15 uF _|_ 1.5K |<|--+--' | 4 A o ::( 350 ohms
IL1 LED 250V --- _|_ | +-------+ ::(
+--|<|---+ | C2 --- | | )::(
| R1 | R2 | .0047 uF | | | .1 ohm )::(
N o---+--/\/\--+--/\/\--+ +-----+--+ )::(
470 3.9K | +--+ +--+--o B
1 W 2 W | | R4 |
+--------------------------------+---/\/\---+
2.2M
The AC input is rectified by D1 and as it builds up past the threshold of the
sidac (D2, 100 V), SCR1 is triggered dumping a small energy storage capacitor
(C1) through the primary of the HV transformer, T1. This generates a HV pulse
in the secondary. In about .5 ms, the current drops low enough such that the
SCR turns off. As long as the instantaneous input voltage remains above about
100 V, this sequence of events repeats producing a burst of 5 or 6 discharges
per cycle of the 60 Hz AC input separated by approximately 13 ms of dead time.
The LED (IL1) is a power-on indicator. :-)
The transformer was totally potted so I could not easily determine anything about its construction other than its winding resistances and turns ratio (about 1:100).
A o
C3 |
+------||-------+
R5 R6 D3 | D4 D5 | D6 R7 R8
HV- o--/\/\---/\/\--+--|>|--+--|>|--+--|>|--+--|>|---/\/\--+--/\/\--o HV+
10M 10M | C4 | 220K | 10M
+------||-------+ |
D3-D6: 10 kV, 5 mA _|_ _|_
C3,C4: 200 pF, 10 kV --- C5 --- C6
C5,C6: 200 pF, 5 kV | |
B o--+----------------------+
The secondary side consists of a voltage tripler for the negative output
(HV-) and a simple rectifier for the positive output (HV+). This asymmetry is
due to the nature of the unidirectional drive to the transformer primary.
From my measurements, this circuit produces a total of around 10 kV between HV+ and HV-, at up to 5 uA. The output voltages are roughly equal plus and minus when referenced to point B.
I assume the module would also operate on DC (say, 110 to 150 V) with the discharges repeating continuously at about 2 kHz. Output current capability would be about 5 times greater but at the same maximum (no load) voltage. (However, with DC, if the SCR ever got stuck in an 'on' state, it would be stuck there since there would be no AC zero crossings to force it off. This wouldn't be good!)
This module is probably for a device similar to the AirEase(tm) Personal Space Ionization Air Cleaner from Ion Systems, Inc. This unit has the positive output of its HV module connected to a 3/16" diameter electrode on the side of the case. This is in contact with a piece of foam (a cylinder about 2" in diameter by 5" high) which surrounds the entire unit. While it appears that this foam should be conductive, I could not detect any evidence of this with a multimeter. The negative output is connected to a 1-1/4" conductive foam disk on the top of the unit. Unfortunately, the HV module in the AirEase was totally potted so I could not determine anything about its internal circuitry.
DL1 +-+ |
o T1 +-------+-----|o|
+12 o---+--------+----------+---------------------+ ::( | +-+ |
| | | D 30T )::( | DL2 +-+
| | -_|_ 4.7uF #30 )::( +-----|o| |
| | --- 50V +------+ ::( 3000T | +-+
| _|_ C2 + | | ::( #44 | DL3 +-+ |
| --- 470pF +--------------|------+ ::( +-----|o|
| | | | F 30T )::( | +-+ |
+_|_ C1 | | D1 | #36 )::( | DL4 +-+
--- 33uF +----------|---+---|<|----|------+ ::( +-----|o| |
- | 16V | | | 1N4002 | o +--+ +-+
| / / | |/ C o | |
| R1 \ R2 \ +--------|Q1 TIP41 +--------------+
| 1K / 4.7K / |\ E | Grid
| \ \ | |
| | | | |
GND o---+--------+----------+--------------+--------------+
T1 is constructed on a 1/4" diameter ferrite core. The D (Drive) and F
(Feedback) windings are wound bifilar style (interleaved) directly on the
core. The O (Output) winding is wound on a nylon sleeve which slips over
the core and is split into 10 sections with an equal number of turns (100
each) with insulation in between them.
DL1 to DL4 look like neon light bulbs with a single electrode. They glow like neon light bulbs when the circuit is powered and seem to capacitively couple the HV pulses to the grounded grid in such a way to generate ozone. I don't know if they are filled with special gas or are just weird neon light bulbs.
The high-tech versions consist of a high voltage low current power supply and fluorescent (usually) lamp selected to attract undesirable flying creatures. (Boring low-tech devices may just use a fan to direct the insects to a tray of water from which they are too stupid to be able to excape!)
However, these devices are not selective and will obliterate friendly and useful bugs as well as unwanted pests.
Here is a typical circuit:
S1 R1 C1 C2 C1-C4: .5 uF, 400 V
H o----o/ o--+--/\/\--------||---+--------||---------+ D1-D5: 1N4007
| 25K D1 | D2 D3 | D4
| +---|>|---+---|>|---+---|>|---+---|>|---+
+-+ | C3 | C4 |
AC Line |o| FL1 +---+----||----+----+---+----)|----+----+--o +
+-+ Lamp | | R3 | | R4 | 500 to
| | +---/\/\---+ +---/\/\---+ 600 V
| R2 | 10M 10M to grid
N o----------+--/\/\---+------------------------------------------o -
25K
This is just a line powered voltage quadrupler. R1 and R2 provide current
limiting when the strike occurs (and should someone come in contact with the
grid). The lamp, FL1, includes the fluorescent bulb, ballast, and starter (if
required). Devices designed for jumbo size bugs (or small rodents) may use
slightly larger capacitors!
(From: Jan Panteltje (pante@pi.net).)
I have one, bought it very cheap: they are only $10 here :)
It comes with a 25 W blue lamp inside, with wires around it. The lamp did not last long, so I replaced that with a 7 W electronic fluorescent type, that now just keeps going and going and going. The bugs do not care, they just go for the light. Then they hit the wires.
Here, we have 230 V, in the lamp is a voltage doubler, with 2, 220 nF capacitors, 2 silicon diodes, and a 10 K Ohm series resistor in the mains. The whole thing cannot be touched by humans from outside. The voltage between the wires is something like 620 V. If an insect shorts the wires, the 10K limits the current until it is destroyed (the insect that is). The insect actually explodes, the 600 V cap discharges into it.
(From: (Abe Shultx) abe_shultz@hotmail.com).)
I grabbed a bug zapper from someone's garbage and opened it up. Instead of a voltage multiplier, there was a transformer. It had a capacitor across the output, and threw an approximately 3/4 inch loud blue arc. I don't know the cap values, because it was potted. :-(
(From: John Harvey (johnharvey@bigpond.com).)
Most DIY fence energizers use an automotive ignition coil and kits (generally minus coil) are available in Australia and probably elsewhere.
Commercial units operate on the capacitor discharge principle and are fired at a 1.2 second interval. Voltage O/P needs to be around 5 to 8 kV (which will drop under load). The energy O/P (pulse duration) is determined by the capacitor and 10 to 20 uF is about right for a small unit (up to 2km or so). They must use a pulse grade capacitor (which has a high dV/dt) to be reliable.
The most common problems relate to failure of the timing motor or gear train. With time, the oil and grease used inside the timing motor may gum up. Eventually, it gets so stiff that the motor stops - or more likely - doesn't start up after a power failure or the unit has been unplugged for a while.
The cheap plastic gears may also break, chip, or loose teeth.
Sometimes, disassembly, cleaning, and lubrication, will get the motor going - possibly for a long time. However, replacement parts are rarely worth the cost compared to a complete new timer.
These may fail in the same way as other electronic controls such as dimmers. Most likely problems are that they are either stuck off or stuck on. Aside from testing for bad connections or shorted or open components (with power OFF or disconnected!), repair is probably economical. Assuming it can be opened non-destructively at all, check the triac and other parts in its vicinity. The rest of the circuitry is probably in a proprietary chip - but these don't fail much.
Also see the section: Warnings about using compact fluorescent lamps on electronic timers.
There are two issues:
Where a solid state timer is used to replace a normal switch, there is usually no connection to the Neutral so it must derive all its operating power from current through the load (though at a very low current level).
The type of circuitry in a compact fluorescent with an electronic ballast (or other equipment with a switching power supply like a TV, some VCRs, computer, etc.) may result in this current being too low or erratic. The result will be that the timer doesn't work properly but damage isn't that likely (but no guarantees).
If it is installed with 3 wires (Hot, Neutral, Load), then this should not be a problem.
In addition, interference (e.g., spikes) from the CF ballast may feed back into the electronic timer and this may either confuse or actually result in failure.
The solid state switching device - usually a triac - in the timer unit may be blown by voltage spikes or current surges when the power goes on or off into an inductive or capacitive load like an electronic ballast (or normal magnetic ballast, for that matter.
Conventional thermostats usually use a bimetal strip or coil with a set of exposed contacts or a mercury switch. In general, these are quite reliable since the load (a relay) is small and wear due to electrical arcing is negligible. On those with exposed contacts, dirt or a sliver of something can prevent a proper connection so this is one thing to check if operation is erratic. The following description assumes a single use system - heating or cooling - using 24 VAC control which is not properly controlling the furnace or air conditioner.
(CAUTION: on an air conditioner, rapid cycling is bad and may result in tripped breakers or overload protectors so ideally, this should be done with the compressor breaker off).
Setback thermostats: These may be controlled electromechanically by a timer mechanism which alters the position of the contacts or selects an alternate set. Newer models are fully electronic and anything beyond obvious bad connections or wiring, or dead batteries is probably not easily repaired. However, eliminate external problems first - some of these may need an additional unswitched 24 VAC or 115 VAC to function and this might be missing.
Heat anticipators: In order to reduce the temperature swings of the heated space, there is usually a small heating element built into the thermostat which provides some more immediate feedback to the sensor than would be possible simply waiting for the furnace to heat the air or radiators. If this coil is defective or its setting is misadjusted, then erratic or much wider than normal temperature swings are possible. There will usually be instructions for properly setting the heat anticipator with the thermostat or furnace.
Fully open mechanisms (no enclosed switches) can be totally dunked in the water as long as they are dried thoroughly afterwards. This should be avoided where the bimetal activates an enclosed 'microswitch' since it is difficult to be sure of removing all the trapped water.
To test an air conditioner thermostat, for example, turn the knob to the highest (coldest) setting. The contacts should be closed. Then, cool the bimetal strip off with cold tap water. The contacts should open. The range can be determined with a thermometer and various combinations of hot and cold water.
Removing the thermostat (unplug AC line first!) and cleaning the contacts using contact cleaner NOT sandpaper or a file (except as a laser resor) - may help temporarily. Replacement is easy if the cold control is self contained using a bimetal strip. If it uses a liquid filled bulb, the tube may snake around inside the cabinet and may be more challenging. Still no big deal. An appliance part distributor or your appliance manufacturer should have a replacement.
Note that an exact replacement may not be needed as long as its electrical ratings (amps or HP) is at least as high, it is intended for the same application (e.g., freezer or space heater), the sensing element is similar, and it can be made to fit! This could come in handy if trying to repair a 30 year old air conditioner!
However, this does not mean that these are the most economical heating devices. Heat pumps based on refrigeration technology can be much less costly to run since they can have coefficients of performance - the ratio of heat output to energy input - of 3 or more to 1. Thus, they are in effect, 300% or more efficient. Note that this does not violate any conservation of energy principles as these simply move heat from one place to another - the outdoors is being cooled off at the same time.
Space heaters come in 3 common varieties:
Of course, first check that the outlet is live.
As with other heating appliances, the most likely problems are with burned out heating elements; defective on/off switches, thermostats, or safety interlock or tip-over switches, bad cord or plug, or bad wiring connections. Your continuity checker or ohmmeter will quickly be able to identify which of these are the problem.
Warning: do not be tempted to bypass any interlock or tip-over switches should they prove defective. They serve a very important fire and personal safety function. Never, ever cover the heater in any way as a serious fire hazard will result.
In addition to the problems covered in the section above: "Radiant space heaters", the fan can also become sluggish or seize up due to gummed up lubrication (as well as other fan-motor problems). Since it is running in a high temperature environment, disassembly, cleaning, and lubrication may be needed periodically despite what the manufacturer may say about permanently lubricated parts.
The typical unit consists of a pair of heating elements providing 600, 900, or 1500 Watts depending on which are switched on. A simple bimetal adjustable thermostat is used for temperature control. The heating elements are fully submerged and sealed inside an oil filled metal finned replica of an old style radiator. The whole affair is mounted on wheels as it is quite heavy.
Depending on design, there may be one or two thermostats (oil and air) in addition to thermal and electrical protection devices.
Common problems with these have been the pair of power switches which tend to fail resulting in no or erratic operation. Note: if your heater is a Delongi, there has been a free (well $5 S&H) upgrade to replace the failure prone power switches and air temperature thermostat on some common models.
The heating elements are replaceable (as a set). Since they are immersed in the oil, you MUST have the radiator on its end with the terminals straight up while changing them or else there will be a mess. Replacement will be worth the cost and effort only if you require the high settings as it is unlikely for both elements to fail. If testing reveals an open element, you will just not have the heat ranges that use it. If an element shorts to the case, it must be disconnected to prevent a shock hazard though the other one can still be safely used. Parts should be available.
It is a portable electric heater, using high-power thermisters as the heating elements. This technology was originally developed by TDK a few decades ago. The premise is that the power thermisters will automatically control the heating element temperature (the thermister), so that if the air flow is blocked, the heater won't cook. The manufacturers make efficiency claims, but these seem to be bogus. (All space heaters are nearly 100% efficient. See the section: Electric space heaters --- Sam.)
I have a bathroom version of this device, and it works.
Battery operated pencil sharpeners use a small DC motor for power. These tend to be whimpier than their AC counterparts but all other comments apply. Always try a fresh set of batteries first.
The motors are typically of the series wound universal type. These have carbon brushes which are prone to wear. However, given the relatively short total usage of a blender, this is not usually a problem.
Disconnecting (and labeling!) connections one at a time may permit the source of a problem to be localized. Diodes can be tested with a multimeter (they should read open in one and only one direction) and resistors checked as well. Shorts in a motor with multiple taps on its windings may be difficult to identify or locate. Shorted windings can result in overheating, incorrect speeds, or even a blender that runs with the power switch supposedly in the off position as the wiring is sometimes sort of strange!
Bad bearings will result in any number of mechanical problems including excessive or spine tingling noise, vibration, a seized rotor or very sluggish rotation. Sometimes, disassembly, cleaning, and oiling will be effective but since these rotate at high speed, don't count on it. Unfortunately, cheap bronze bushings are often used instead of ball bearings. However, substituting a set from another similar unit might work since it is usually the bronze bushing and not the motor shaft that fails.
The most sophisticated units will have a variable speed control - similar to a light dimmer. If this goes bad - the blender always runs at full speed - then the active element (triac) has probably blown. Replacement is possible and the part types should be readily available.
If there is no heating, check the element and thermal protector with an ohmmeter. If the element is open, it is probably time for a new coffee maker. The thermal protectors can be replaced but the underlying cause may be a defective, shorted overheating element so it may not be worth the trouble. Timers can develop bad contacts and bad connections are possible on electronic controller circuit board wiring.
I wish I had thought of this sooner rather than throwing out the first coffee maker and I had planned to throw this one out. For some reason I thought I would just look inside to see what was up.
Where I live the water is hard (well) and there is constant scaling and buildup of calcium. We heard that all you have to do is to run a mixture of vinegar through the coffee maker to rejuvenate.
A friend and the 2 of ours all started to leak very badly when the vinegar/water mixture when through. I though that the internal plumbing had corroded through the metal parts and the vinegar dissolved the calcium that was protecting the holes and therefore unrepairable. Who knows where these ideas come from.
Now for the technical solution.
The element that is used to boil the water and uses the bubbles to bring hot water to top of coffee maker is the same element that is used to keep the pot warm.
There is a metal tube attached to the metal warming element and this unit has a heating element embedded. There are 2 rubber hoses attached. One brings cold water to heater and the other brings boiling water to top. The cold water tube has a check valve that prevents the bubbling water from going to cold water reservoir.
When vinegar is added the calcium scales start to dissolve and in 3 of 3 so far, this blocked the metal tube. The water starts to boil and since the cold water inlet has a check valve the water pressure can only buildup to where the rubber tube is blown off the metal pipe. No damage to parts.
To fix:
AC operated clocks depend on the AC line frequency (60 Hz or 50 Hz depending on where you live) for time keeping. The accuracy of a line operated clock is better than almost any quartz clock since the long term precision of the power line frequency is a very carefully controlled parameter and ultimately based on an atomic clock time standard.
Therefore, most problems are related to a clock motor that does not run or will not start up following a power outage. Once running, these rarely fail.
The most common problems are either gummed up oil or grease inside the motor and gear train, broken gears, or broken parts of the clock mechanism itself. See the sections on "Synchronous timing motors" for repair info.
Battery operated quartz clocks usually operate on a 1.5 V Alkaline cell (do not replace with NiCds as they do not have a long absolute life between charges even if the current drain is small as it is with a clock).
First, test the battery. Use a multimeter - usually anything greater than 1 V or so will power the clock though if it is closer to 1 V than 1.5 V, the battery is near the end of its life. The clock may run slow or fast or erratically on a low battery.
With a good battery, failure to run properly is usually mechanical - one of the hands is hitting against the glass front or something like that. Don't forget to check any on/off switch - these are not expected but are often present presumably to permit you to start the clock at precisely the right time. I had one case where the fine wire to the solenoid that operates the once per second clock mechanism broke and had to be resoldered but this is exceedingly rare.
If the clock consistently runs slow or fast with a known good battery, there is usually a trimmer capacitor that can be adjusted with a fine jeweler's straight blade screwdriver. Without test equipment the best you can do is trial and error - mark its original position and turn it just a hair in one direction. Wait a day or week and see if further adjustment is needed (right, like you also won the lottery!) and fine tune it.
If the hands should fall off (what a thought!), they can usually be pressed back in place. Then, the only trick is to line up the alarm hand with the others so that the alarm will go off at the correct time. This can usually be done easily by turning the hour hand counterclockwise using the setting knob in the rear until it is not possible to turn it further. At this point, it is lined up with the alarm hand. Install all hands at the 12:00 position and you should be more or less all set.
AC powered carving knives include a momentary power switch, small motor (probably universal type), and some gearing. Congealed food goo as well as normal lubrication problems are common. The power switch is often cheaply made and prone to failure as well. The cord may be abused (hopefully not cut or damaged by careless use of the knife!) and result in an intermittent connection at one end or the other. For motor problems, see the appropriate sections on universal motors.
For battery powered knives, bad NiCds cells are a very likely possibility due to the occasional use of this type of appliance.
See the section: Small permanent magnet DC motors and the document: AC Adapters, Power Supplies, and Battery Packs for information on repair.
Sluggish operation may be due to cookie dough embedded in the gearing. Fine particles of flour often find their way into the gears - clean and lubricate. There may be a specific relationship that needs to be maintained between the two main beater gears - don't mess it up if you need to disassemble and remove these gears or else the beaters may not lock in without hitting one-another.
The speed control may be a (1) selector switch, (2) mechanical control on the motor itself (a governor/spring/switch arrangement), or (3) totally electronic. Parts may be replaceable although, for portables at least, a new mixer may make more sense.
For sluggish operation (non-mechanical), sparking, burnt smells, etc., see the section: Problems with universal motors.
As usual, cord and plug problems, bad bearings, burnt motor windings, and broken parts are all possibilities.
An iron consists of a sole plate with an integrated set of heating coils.
Steam irons will have a series of holes drilled in this plate along with a steam chamber where a small amount of water is boiled to create steam. A steam iron can be used dry by simply not filling its reservoir with water. Those with a spray or 'shot of steam' feature provide a bypass to allow hot water or steam to be applied directly to the article being ironed.
Over time, especially with hard water, mineral buildups will occur in the various passages. If these become thick enough, problems may develop. In addition, mineral particles can flake off and be deposited on the clothes.
A thermostat with a heat adjustment usually at the top front of the handle regulates the heating element. This is usually a simple bimetal type but access to the mechanism is often difficult.
Where an iron refuses to heat, check the cord, test the heating element for continuity with your ohmmeter, and verify that the thermostat is closed.
An iron that heats but where the steam or spray features are missing, weak, or erratic, probably has clogged passages. There are products available to clear these.
Newer irons have electronic timeout controllers to shut the iron off automatically if not used for certain amount of time as a safety feature. Failure of these is not likely and beyond the scope of this manual in any case.
When reassembling an iron, take particular care to avoid pinched or shorted wires as the case is metal and there is water involved - thus a potential shock hazard.
Since most of these are so inexpensive, anything more serious than a broken wire or plug is probably not worth repairing. The heating element may develop a broken spot - particularly if something like a fork is carelessly used to fish out an English muffin, for example. (At least unplug it if you try this stunt - the parts may be electrically live, your fork is metal, you are touching it!). They may just go bad on their own as well.
Being a high current appliance, the switch contacts take a beating and may deteriorate or melt down. The constant heat may weaken various springs in either the switch contact or pop-up mechanism as well. Sometimes, some careful 'adjustment' will help.
Controllers may be thermal, timer based, or totally electronic. Except for obvious problems like a bent bimetal element, repair is probably not worth it other then as a challenge.
The following applies directly to several Sunbeam models (and no doubt to many others as well).
(From: John Riley (jriley@calweb.com).)
I will assume that the toaster is either a model ATW or possibly an older model 20 or the like.
When you drop the bread in the toaster it trips a lever that is attached to the bread rack. This lever pushes in on the contacts inside of the thermostat (color control switch) which actually turns the toaster on. In "most cases" adjusting the screw on the bottom of the toaster will do the trick. The proper adjustment is to adjust the carriage tension so that the bread rack in the side where it marked for a single slice of bread comes just to the uppermost limit of its travel. Any more is overkill.
If you have adjusted it as mentioned above and it still won't go down, there is one more thing you can try. Take the toaster a sort of BUMP it down onto the table rather firmly. Sometimes a piece of crumb will get in between the thermostat contacts. A couple of good "bumps" on the table will usually dislodge the particle.
If all of the above doesn't work, and you know the cord isn't bad, them you may very well have a thermostat that has gone south. They are still available for replacement on most models. Suggest you check with your local SUNBEAM AUTHORIZED SERVICE for price and availability.
Modern toaster oven (broilers) use Calrod style elements - usually two above and two below the food rack. Depending on mode, either just the top (top brown/broil), just the bottom (oven), or both sets (toast) will be energized. Each pair may be wired in series meaning that a failure of one will result in both of the pair being dead. Very old units may use a coiled NiChrome element inside a quartz tube.
Thermostats are usually of the bimetal strip variety with an adjustment knob. A cam or two on the shaft may also control main power and select the broil function in the extreme clockwise position.
There may be a mode switch (bake-off-broil) which may develop bad contacts or may fuse into one position if it overheats. These are often standard types and easily replaceable. Just label where each wire goes on the switch before removing it to take to an appliance repair parts store.
Newer models may use an electronic timer for the toast function at least. I assume it is not much more than something like an IC timer (555) operating the trip solenoid. However, I have not had to deal with a broken one as yet.
Testing is relatively straightforward. Check the heating elements, thermostat, mode switch,, cord, and plug. While replacements for heating elements and thermostats are often available, removing the old one and wiring the new one may not be straightforward - rivets may be used for fastening and welds for the wire connections. You will have to drill the rivets with an electric drill and replace them with nuts, bolts, and lockwashers. Crimp splices or nuts and bolts can be used for the wiring. Take extra care in reassembly to avoid any bare wires touching the metal cabinet or other parts as well as insulation being cut by sharp sheetmetal parts. The high temperature fiberglas or asbestos insulation is not very robust. In the end, it may not be worth it with full featured toaster oven/broilers going for $20-30 on sale.
Some more details and comments are provided in the section: Troubleshooting a toaster oven.
Before doing this, there are basic things to check:
The broiler option is similar to top brown.
Thinking about which elements need to be powered for which mode, and whether the thermostat is involved (not for toasting), will help to narrow down the area of attack.
If a heating element is found to be bad either by inspection or the ohmmeter check, it can be replaced though this may only make sense from a cost perspective if you have one that can be salvaged from another appliance. If the length and resistance are similar, it should work. Attaching the cut wires may be a challenge unless you are into welding. However, a mechanical connection with a screw and nut will work though for how long is anyone's guess. Also see below. Solder can't be used.
Visually inspect the heating elements. Failure of a Calrod(tm) type often results in an external wart of blemish where the internal coil shorted and melted the cladding. Nichrome (wire) elements fail by breaking somewhere along their length.
And/or measure the resistance of each of the elements. Typical values are 10 to 12 ohms for a single Calrod type or 20 to 25 ohms for a complete Nichrome coil. (Your measurements will vary depending on the actual wattage of the oven. These values are typical in the U.S.A. for operation on 115 VAC.)
(From: Terry (tsanford@nf.sympatico.ca).)
Get a 'wire-nut' connector. Not one of the usual ones with a wire spiral inside it; but one of the ones that has a brass insert with a screw to secure the wires. See 'Note' re set screw. Throw away the plastic outer shell. Put end of the element heating wire and the end of a short piece of heat resistant wire into the wire nut brass insert and tighten the screw; real tight cos it's going to get somewhat hot! Dress the wire and/or suspend what is now your brass connector so that it is clear of everything or use some woven 'glass' heat resistant tubing to cover the connection. Repeat at other end as necessary. Probably last for quite a while. Note: Look for one that has a set-screw that can be tightened with a hexagonal 'Allen' wrench rather than a straight edge screwdriver. With these it would seem you can get the screw and therefore contact with the wires much tighter! Another connection that might work, but have not used for this is to clip the screw terminals off the end of a duff oven element and use those as screw terminals to secure a connection to the toaster heating element wire? Those oven element terminals do get hot in normal use anyway!
Apparently, the only real difference between a "toaster oven" and a "toaster oven/broiler" is that the latter has a means of disabling the bottom heating element while in oven (non-timed) mode - and, of course, the price!
+- - - - - - + - - - - - - - + All part of Oven Control
: : :
S1A S1B _:_ : R1 R2
AC H o--+------/ -----------o o------+---+---:-----/\/\/\/\----/\/\/\/\---+
| Oven Power Thermostat | | : Top Element |
| | | : |
| S2 ___ Toast On | | S1C R3 R4 |
+------------o:o-------------+ +---/ ----/\/\/\/\----/\/\/\/\---+
: | Broil Bottom Element |
+-------+ : R5 / Top Brown |
+-->| Timer |--+ : Toast 47K \ (Full CW) R1-R4: 8-12 ohms |
| +-------+ )|| Release / |
Light/Dark )|| Solenoid | +--+ IL1 Power |
Temp. Sensor + +---|oo|---+ Indicator |
| NE2 +--+ | |
AC N o--------------+---------------------------+-------------------------+
Aside from the CMOS IC based toast timer, this is a fairly basic design:
The toast function and oven/broiler are controlled separately. A single Power/Temperature/Broil knob controls the oven/broiler. This is entirely electro-mechanical with a conventional bimetal thermostat. Toast darkness is based only on time using CD4541B timer chip to release a manually activated Toast lever. Older 'dumber' toasters often were more sophisticated in their operation using a combination of time and temperature. Not this one.Its conventional counterpart would be identical except using a mechanical and/or toast temperature sensor in place of the IC timer. Despite what you might think, the most likely failures are NOT in the 'high-tech' electronics but the usual burnt out heating element(s), bad cord or plug, broken wires, and tired switches.
If you notice an increase in motor noise (whining or squealing, grinding, knocking) then the motor and fan should be inspected and parts replaced if necessary. Sudden failure is unlikely but if it were to happen - seized bearings, for example - an overtemperature thermal protector should shut down the heating element or entire oven. Some of these may not be self resetting (thermal fuse).
Where a NiChrome coil type heating element is used, a break will be obvious. If it is very near one end, then removing the short section and connecting the remainder directly to the terminal will probably be fine. See the section: Repair of broken heating elements.
For appliances like waffle irons, burger makers, and similar types with two hinged parts, a broken wire in or at the hinge is very common.
Note that since these operate at high temperatures, special fiberglass (it used to be asbestos) insulated wiring is used. Replace with similar types. Take extra care in reassembly to avoid shorted wires and minimize the handling and movement of the asbestos or fiberglas insulated high temperature wiring.
As always, check for bad connections if the popper is dead or operation is erratic.
Problems with heating can arise in the heating element, thermostat, and thermal protector.
If the stirrer doesn't turn, a gummed up motor or stirrer shaft (since these are only used occasionally) may be the problem. See the chapter: Motors 101.
As always, check for bad connections if the popper is dead or operation is erratic.
Problems with heating can arise in the heating element, thermostat, and thermal protector.
The motor is probably a small PM DC type and there will then be a set of diodes or a bridge rectifier to turn the AC into DC. Check these and for bad bearings, gummed up lubrication, or other mechanical problems if the motor does not work or is sluggish. See the chapter: Motors 101.
Obviously, if you can disassemble the unit to the point of access to the connections to the heating element, a simple continuity check of each component (heating element, thermostat/switch, fuse if any, line cord, etc.) will identify whether there is a bad part. Similarly, if there is no switch, thermostat, or any other accessible parts - the entire thing is a sealed glob with a line cord - if there is no continuity, it is bad.
However, for the more general case, there are two ways to test a heat tape if whether it is alive or not isn't obvious by feel and you can't get inside. If you cannot get to the connection to the actual heating element, then the tests need to be performed with any power switch or thermostat in the 'on' position. However, it may not be possible to get a thermostat to go on if you are inside a nice heated house. It may need to be bypassed or the tests run where it is cold!
The basic components of a bread machine are:
Common problems: Blown thermal fuse (screwed to outside of chamber in series with everything, open heating element, leaking stirrer seal, bad or stuck release solenoid.
Common problems: Bad belt or one that has popped loose, bad motor or motor in need of lubrication.
Common problems: Blown triacs, contamination in touchpad due to overzealous cleaning, faulty microprocessor, surge or lightning damage.
Like any other electronic device, a power surge or lightning strike can wipe out the controller rendering the bread machine dead as, well, a loaf of bread. Unless there are obviously blown parts AND you get very lucky, the only solution with any likelihood of success is a total brain transplant (controller board replacement) - which is probably more expensive than a new bread machine.
I have a 1903 Singer foot-pumped sewing machine which we have since electrified and still runs fine. A couple of drops of sewing machine or electric motor oil every so often is all that is needed. They were really built well back then.
Although the appearance of the internal mechanism may appear intimidating at first, there really is not that much to it - a large pulley drives a shaft that (probably) runs the length of the machine. A few gears and cams operate the above (needle and thread) and below (feet and bobbin) deck mechanisms. Under normal conditions, these should be pretty robust. (Getting the adjustments right may be another story - refer to your users manual). Sometimes if neglected, the oil may seriously gum up and require the sparing use of a degreaser to loosen it up and remove before relubing.
If the motor spins but does not turn the main large pulley, the belt is likely loose or worn. The motor will generally be mounted on a bracket which will permit adjustment of the belt tension. The belt should be tight but some deflection should still occur if you press it gently in the middle.
If the motor hums but nothing turns, confirm that the belt is not too tight and/or that the main mechanisms isn't seized or overly stiff - if so, it will need to be cleaned and lubrication (possibly requiring partial disassembly).
The electric motor is normally a small universal type on a variable speed foot pedal (see the section: Wiring a sewing machine speed control).
If the motor does not work at all, bypass the foot pedal control to confirm that it is a motor problem (it is often possibly to just plug the motor directly into the AC outlet). Confirm that its shaft spins freely. All normal motor problems apply - bad wiring, worn brushes, open or shorted windings, dirty commutator. See the section: Problems with universal motors.
The common foot pedals are simply wirewound rheostats (variable resistors) which have an 'off' position when the pedal is released. They are simply wired in series with the universal motor of the sewing machine (but not the light) and can be left plugged in all the time (though my general recommendation as with other appliances is to unplug when not in use.
While not as effective as a thyristor type speed controller, these simple foot pedals are perfectly adequate for a sewing machine. There are also fancier speed controls and using a standard light dimmer might work in some cases. However, there are two problems that may prevent this: the sewing machine motor is a very light load and it is a motor, which is not the same as a light bulb - it has inductance. The dimmer may not work, may get stuck at full speed, or may burn out.
If dead, check for continuity of the plug, cord, switch, and coil. IF sluggish, clean thoroughly - hair dust is not a good lubricant. Sliding parts probably do not require lubrication but a drop of light oil should be used on any rotating bearing points.
Note that since a resonance is involved, these types of shavers may not work well or at all on foreign power - 50 Hz instead of 60 Hz or vice versa - even if the voltage is compatible.
A shaver that runs sluggishly may have a dead NiCd cell - put it on charge for the recommended time and then test each cell - you should measure at least 1.2 V. If a NiCd cell reads 0, it is shorted and should be replaced (though the usual recommendation is to replace all cells at the same time to avoid problems in the future).
Note that in terms of rechargeable battery life, shavers are just about optimal as the battery is used until it is nearly drained and then immediately put on charge. The theoretical 500 to 1000 cycle NiCd life is usually achieved in shaver applications.
(Merged comments from: Jerry Greenberg (jerryg50@hotmail.com) and Paul Grohe (grohe@galaxy.nsc.com).)
I used to service some of the Philips models of shavers. These are the same as the Norelco. When the batteries are dead the shaver will not run. The shaver has a sophisticated uPC (for what it does) that manages its operation. When it sees the batteries as dead, it will inhibit the shaver from being able to run. If the batteries are shorted, nothing will even light up at all.
The little "power supply" does not have enough "juice" to run the motor. The motor runs off the cells. If the cells are *dead* (shorted), nothing will work.
You can "test" the power supply by either listening carefully, or, holding it up to an AM (MW) radio tuned off to the end (no station) while plugging the razor in.
If the charger is okay, but the cells are shorted or weak, you will hear a quick "ping" followed by a stretched-out, "constipated" squeal. This is the little switching power supply quitting under the "dead weight" of the cells.
A "good" razor will have a nice, steady squeal (or "hiss" on the radio).
Once the shaver is opened, if you are mechanically skilled, it is worth the effort to disassemble the top head assembly where the motor goes in to, and do a thorough cleaning. You can lubricate the gears and shafts with a very light silicon lubricant. The motor is held in position with two spring clips. Care must be taken to not break the plastic pieces.
Everything snaps together. Opening the case is usually the toughest part.
And take it apart over a paper towel. Powdered hair will fall out all over the place as you take it apart. Keep a dust-buster or vacuum near by to suck up any escaping "dust". The stuff is worse than wallboard dust!
If you do any soldering, do it in a well ventilated place.
Burning hair is not a pleasant smell!
I'm on my third set of cells after 12 years. Last month I
installed new 1200 mA/H NiMh cells.
Also: While you have the motor removed - it is a good idea to
"clean" the motor brushes by connecting it to an adjustable power
supply and slightly over-voltaging it to make it run faster than
normal (with no load). Run it full-out for about 5 minutes (or
until it runs smoothly). Run it in both directions, too. This
will eliminate any "chugging", stalling or rough starts you may
be experiencing with older units.
As for original parts, Norelco will supply them if the shaver model is
less than about 5 to 7 years old. Usually the replacement parts are not
expensive in relation to replacing the shaver. As for replacement
parts, they would only supply the complete circuit boards, batteries,
and any mechanical parts if they are defective.
Mine is as good as new now!
Problems can occur in the following areas:
Of course, getting inside may prove quite a challenge and in general one must
consider the hand unit to be a throw-away item since it is generally glued
together - permanently. While it is possible to use a hacksaw to carefully
cut around the case, the resulting repair once the thing is put back together
will be decidedly of the 'Jerry-rigged' type and sealing will be difficult
and long term reliability and safety would be questionable.
(From: Jeff & Sandy Hutchinson (sandy2@flatoday.infi.net).)
It's darned near impossible to replace the batteries on the Interplak
toothbrush without destroying the recharging circuit. The base of the hand
unit has a little pickup coil in it, and when you unscrew the cap to get at
the batteries, you break the connections to the pickup coil. Best to do an
exchange with the factory.
(From: Bill Finch (alioth@ix.netcom.com).)
I've done this twice. Use a tubing (or pipe) cutter at the seam. Rotate and
tighten the cutter slowly until the thing falls apart. Fish out the guts and
resolder a new battery in place. Slip everything back into the lower tube.
Glue the top back on with PVC pipe sealant. It helps to make a simple jig to
hold the top steady while the PVC cement sets. Try not to get excess cement
on the external plastic or you wife will complain. A good trick here is to
mask with drafting tape or whatever.
If this fails just buy a new toothbrush.
(From: Chip Curtis (ccurtis@zilog.com).)
I had a problem with my Braun and found that the unit's PCB was rather
wet. After drying it out and coating it the unit still turned on from
time to time and I noticed that during the false runs the transistor was
not saturating. It didn't take long to see that the problem is caused by
the transistor's base being left wide open. Any noise on the base or
small current flow from PCB leakage will cause the transistor to fire and
the brush noise is enough to keep it triggering and running on.
The fix; tack a 1M or whatever (no smaller than 47K) resistor from the
base of the transistor to ground. The pull-down won't hurt current
consumption when the unit is off because the reed switch is open, and the
small bias won't make much of a difference when the unit is running.
A coil in the charging base (always plugged in and on) couples to a mating
coil in the hand unit to form a step down transformer. The transistor, Q1,
is used as an oscillator at about 60 kHz which results in much more efficient
energy transfer via the air core coupling than if the system were run at 60
Hz. The amplitude of the oscillations varies with the full wave rectifier 120
Hz unfiltered DC power but the frequency is relatively constant.
For the toothbrush, a 4 position switch selects between Off, Low, Medium, and
High (S1B) and another set of contacts (S1A) also is activated by the same
slide mechanism. The motor is a medium size permanent magnet type with carbon
brushes.
This Braun electric toothbrush (original model) would turn itself on and keep
running until its batteries were discharged.
The toothbrush can be disassembled by pulling the base off with slip joint
pliers (do not pull too hard because there is only about 1" of slack in
the charging coil wires). With the base off, the mechanism slides out of
the case.
There is a simple charging circuit, charging LED, 2 NiCd cells, and a reed
switch driving the base of an NPN transistor. The transistor collector
drives the motor.
I charged the battery, but the problem of the motor running with the reed
switch open didn't recur until I held my finger on the transistor for
about 10 seconds seconds. Grounding the transistor base turned it off
again, and I could repeat this cycle. Since there wasn't anything else to
go wrong I decided to replace the transistor. I couldn't read the
marking, but it's in a SOT89 package and the motor current is 400-700 mA so
it must be something like a BC868. However, I didn't have any surface
mount or TO92 transistors that could handle the current, so I used a
2SD882 (small power tab package), which I was able to squeeze into some
extra space in the center of the charging coil.
Some have built in infra-red heat which may just be a set of small light
bulbs run at low voltage to provide mostly heat and little light (a filter
may screen out most of the light as well). Obviously, individual light
bulbs can go bad - if they are wired in series, this will render all of
them inert.
At least one brand - Conair - has had problems with bad bearings. Actually,
poorly designed sleeve bearings which fail due to the eccentric load. If you
have one of these and it becomes noisy and/or fails, Conair will repair
(actually replace) it for $5 if you complain in writing and send it back to
them. They would like a sales receipt but this apparently is not essential.
First determine if the problem is with the heat, air, or both.
For heat problems, check the element for breaks, the thermal protector
or overtemperature thermostat (usually mounted in the air discharge), the
connections to the selector switch, and associated wiring.
Newer models may have a device in the plug to kill power to the unit should it
get wet. See the sections: "What is a GFCI?" and "The Ground Fault Circuit
Killer (GFCK)".
For air problems where the element glows but the fan does not run, check the
fan motor/bearings, connections to selector switch, and associated wiring.
Confirm that the blower wheel turns freely and is firmly attached to the
motor shaft. Check for anything that may be blocking free rotation if the
blower wheel does not turn freely. The motor may be of the induction,
universal, or PM DC type. For the last of these, a diode will be present
to convert the AC to DC and this might have failed. See the appropriate
section for problems with the type of motor you have.
This safety 'enhancement' must have been designed by engineers with too much
time on their hands (or the wrong sort of incentive bonus plan). Get a few
drops of water on one of these appliances and it goes in the garbage.
The irony is that once the GFCK blows, the owner is likely to just cut off the
GFCK plug and replace it with a normal plug (rather than throwing the
appliance away or having it properly repaired, as was no doubt the intent),
thus eliminating the protection altogether!
The GFCK (my designation) is a device contained in an oversize plug which is
part of the cordset of some newer hand-held (at least) appliances that may be
used in wet areas like kitchens and baths but where there may be no GFCI
protection (see the section: What is a GFCI?. I
first ran across one of these on a late model Conair blow dryer (which is why
this section on GFCKs is here rather than with the GFCI information).
In a nutshell, the GFCK permanently disconnects power to the appliance - at
the plug - should electrical leakage of more than a few milliamps be present
within the appliance. Unlike a GFCI, ther is NO reset button and no way to
get inside short of drilling out the rivets holding the plug together! In
fact, the unit I dissected uses an SCR to grossly overdrive and blow out a
normal resistor which by its placement holds a mechanical latch in place for a
pair of contact releases that disconnect the plugs prongs from the wires of
the cord. With the resistor gone, the prongs of the plug go nowhere so
everything beyond them becomes totally dead, electrically - forever. Thus,
even if dropped into a bathtub, the appliance will not cause electrocution.
Sorry, these can't be used as part of murder mystery plots!
Admittedly, the GFCK works regardless of whether the outlet the appliance is
plugged into is 2-prong, 3-prong, correct or reverse polarity, or GFCI
protected, and thus provides a high level of safety. But, this may be taking
cost reduction to an extreme rather than providing a resettable basic GFCI
(just H-G faults). Having said that, there is merit to disabling the
appliance permanently since there is no way to know how much damage may have
been done internally by the water (or whatever caused the GFCK to trip) and
it's safety may always be suspect.
All this is mounted inside the plug:
The Ground wire in the cord (G) goes from the circuit in the plug back to the
metal parts of the dryer (though as usual with a modern appliance, it is
mostly made of plastic). Note that there is no Ground wire to the outlet -
just to the appliance. The theory goes that should the device get wet,
current is more likely to flow to the nearby metal parts and via the cord's
Ground wire to the GFCK than to some other earth ground (including a person
touching an earth ground). In fact, this device does NOT sense a current
imbalance like a true GFCI - just leakage to its internal Ground wire, but
under realistic circumstances, this should be a reliable indication of a
fault.
A fault condition would result in current flowing between H and G in the cord.
When this exceeds about 3 mA, the SCR (Q1) triggers putting R1 essentially
across the line (maybe limited a bit by L1). R1, which was physically holding
the latch for the plug circuit breakers CB1 and CB2, now explodes releasing
both these contacts. Power is shut off to the appliance - permanently!
Hopefully, the plug doesn't catch fire in the process! :)
As noted, cutting off this fancy plug and replacing it or the entire cordset
with a conventional one provides the same level of safety IF AND ONLY IF the
appliance is used ONLY in a GFCI protected outlet (the cord Ground wire is
left disconnected in this case or can be attached to the third prong of a
three prong plug). The alternative of installing a 3-prong plug on
the appliance and then only using it in a properly grounded 3-prong outlet
doesn't provide the same protection as there can still be enough leakage to be
lethal without blowing a fuse or tripping a breaker (and the ground wire in
the sample I have wouldn't be adequate to carry a major fault current anyhow).
And, guess what? This Conair blow dryer died not because the GFCK had been
activated, but because the soldering to the R1 was defective and it pulled
loose!
Note that some designs are very hard on cassettes - yanking at the tape
since only increased tension is used to detect when the tape is at the end.
These may eventually stretch the tape or rip it from the reel. I don't
really care much for the use of tape rewinders as normal use of rewind and
fast forward is not a major cause of VCR problems. Sluggish or aborted
REW and FF may simply indicate an impending failure of the idler tire or
idler clutch which should be addressed before the VCR gets really hungry
and eats your most valuable and irreplaceable tape.
Problems with tape rewinders are usually related to a broken or stretched
belt or other broken parts. These units are built about as cheaply as
possible so failures should not be at all surprising. The drive motor can
suffer from any of the afflictions of similar inexpensive permanent magnet
motors found in consumer electronic equipment. See the section:
Small permanent magnet DC motors. A broken belt is
very common since increased belt (and tape) tension is used to switch the unit
off (hopefully). Parts can pop off of their mountings. Flimsy plastic parts
can break.
Opening the case is usually the biggest challenge - screws or snaps may
be used. Test the motor and its power supply, inspect for broken or
dislocated parts, test the power switch, check and replace the belt if
needed. That is about it.
A vacuum cleaner consists of:
I have always been able to remove the bad section and then graft what is
left back on to the connector. Without seeing your vacuum, there is no way
to provide specific instructions but that is what creativity is for! :-)
It might take some screws, tape, sealer, etc.
$100 for a plastic hose is obviously one approach manufacturers have of
getting you to buy a new vacuum - most likely from some other manufacturer!
Note: Some vacuum cleaners with power nozzles use the coiled springs of the
hose as the electrical conductors for the power nozzle. If you end up cutting
the hose to remove a bad section, you will render the power nozzle useless.
I suppose there will be degree-credit university courses in the operation
of these space age vacuums as well! --- sam
A NiCd battery pack powers a small DC permanent magnet motor and centrifugal
blower. A simple momentary pushbutton power switch provides convenient
on/off control.
Aside from obvious dirt or liquid getting inside, the most common problems
occur with respect to the battery pack. If left unused and unplugged for
a long time, individual NiCd cells may fail shorted and not take or hold
a charge when the adapter is not plugged back into the wall socket. Sluggish
operation is often due to a single NiCd cell failing in this way.
See the appropriate sections on "Batteries" and "Motors" for more information.
While replacing only selected cells in any battery operated appliance is
generally not recommended for best reliability, it will almost certainly
be much cheaper to find another identical unit at a garage sale and make
one good unit out of the batteries that will still hold a charge. It is
better to replace them all but this would cost you as much as a new
Dustbuster.
The NiCd cells are soldered in (at least in all those I have seen) so
replacement is not as easy as changing the batteries in a flashlight but
it can be done. If swapping cells in from another similar unit, cut the
solder tabs halfway between the cells and then solder the tabs rather than
to the cells themselves if at all possible. Don't mess up the polarities!
In the case of genuine Dustbusters, where a new battery is needed and you
don't have a source of transplant organs, it may be better to buy the
replacement cells directly from Black and Decker. They don't gouge you on NiCd
replacements. B&D is actually cheaper than Radio Shack, you know they are the
correct size and capacity, and the cells come with tabs ready to install.
They'll even take your old NiCds for proper re-cycling.
There are no serviceable parts inside the sealed cover - forget it as any
repair would represent a safety hazard. The control unit may develop bad
or worn switches but even this is somewhat unlikely. It is possible to
disassemble the control to check for these. You may find a resistor or diode
in the control - check these also. With the control open, test the wiring to
the pad itself for low resistance (a few hundred ohms) between any pair of
wires). If these test open, it is time for a new heating pad. Otherwise,
check the plug, cord, and control switches.
Extended operationg especially at HIGH, or with no way for the heat to escape,
may accelerate deterioration inside the sealed rubber cover. One-time thermal
fuses may blow as well resulting in a dead heating pad. One interesting note:
Despite being very well sealed, my post mortems on broken heating pads have
shown one possible failure to be caused by corrosion of the internal wiring
connections after many years of use.
Older style controllers used a bimetal thermostat which actually sensed
air temperature, not under-cover conditions. This, it turns out, is a
decent measurement and does a reasonable job of maintaining a comfortable
heat setting. Such controllers produced those annoying clicks every couple
of minutes as the thermostat cycled. Problems with the plug, cord, power
switch, and thermostat contacts are possible. The entire controller usually
unplugs and can be replaced as a unit as well.
Newer designs use solid state controls and do away with the switch
contacts - and the noise. Aside from the plug and cord, troubleshooting
of a faulty or erratic temperature control is beyond the scope of this
manual.
The components of the typical $45 unit are:
The piezo transducer sets up a standing wave on the surface of the water pool.
The level is sensed with a float-switch to ensure no dry-running (kills the
piezo) and the blower/fan propels the tiny water droplets out of the cavity.
A few manufacturers are nice enough to include a silly air filter to keep any
major dust out of the 'output' - do clean/check that once in a while.
Common problems:
CAUTION: Unless you know what you are doing (and have gotten shocked a
few times in your life) DO NOT play with the piezo driver module. Most
run at line voltage with sometimes 100+V on heatsinks - which are live.
Note: piezo's in general are driven with voltage, as opposed to current. This
explains why you can expect high voltages - even in otherwise low-voltage
circuits. Case in point: the Polaroid ultrasonic sonar modules.
(From: Dave VanHorn" (dvanhorn@cedar.net).)
The Devilbiss units I used to repair, used about 1 W at 1 MHz (if I recall
correctly into a thick barium titanate transducer. Their most common problem
was cracked transducers.
There was a shaped cavity above the transducer, I would guess some sort of
Helmholtz resonator. You had to tune the operating frequency around to maximize
the plume, and then trim for a certain plume height with the output drive.
Don't stick your finger in the plume. Although the water is not hot, you
will discover that your finger is mostly water. It's kind of like slamming
your finger in a car door.
(From: Daniel Cilevitz (rpf.20.foobar0@antichef.com).)
Thinking about the above info on ultrasonic humidifiers and
their power output, I decided to experiment with an ultra-cheap
ultrasonic humidifier (useless for its intended application) and the
clear polystyrene front cover of a CD jewel case. With the water level
correctly set, placing the plastic sheet at the tip of the plume (cone
shaped tip of the water) just above the transducer resulted in a
cone-shaped section of material deforming outwards from the center
of the wave. In normal operation, a mist of water is ejected from this
location. The bottom of the sheet intersects the cone, and the
truncated part of the wave doesn't like this and melts its way
through. With the sheet in motion, a cut/trough about 3 mm wide
appears. Moving slowly results in a slightly larger amount of material
being displaced, up to about 5 mm. It doesn't go all
the way through the plastic for some reason. The effect
is the same as pressing a hot piece of metal against the plastic. The
process is continuous and you can draw patterns by moving the material
around on top of the standing wave. The deformed plastic was only
warm, not hot, though it may have been cooled by contact with the
water.
After seeing this firsthand, you will never feel the urge to stick
your finger in the plume again! I would not want to discover the
effects of a larger humidifier or ultrasonic cleaner on parts of your
body. This was with a $25 unit from a store closing special, so imagine what
a larger, more powerful one could do!
As an aside: Jewel cases are made from two kinds of polystyrene:
General Purpose Polystyrene (GPPS) and High-Impact Polystyrene
(HIPS). GPPS is crystal- clear but very brittle, and is used to mold
the front and back covers. HIPS is translucent to opaque but more
flexible, and is used to mold the tray. The tray needs to be flexible
so that the tray hub can grab the disc hub without breaking off. It's
unfortunate that the hinged part of the jewel case is made of such a
brittle material, as it's always the first thing to break ;)
(From: Roger Vaught (vaurw@onramp.net).)
At a local shop they sell small water fall displays made from limestone in a
marble catch basin. These are made in China. They use a small water pump for
the flow.
When I first saw one I thought the store had placed dry ice in the cavity
where the water emerged as there was a constant stream of cloud flowing from
it. Very impressive. It turns out they use the ultrasonic piezo gizmo to make
the cloud. The driver is a small 3 X 5 X 3 inch box with a control knob on
top. If you look into the cavity you can see the piezo plate and a small red
LED. The water periodically erupts into vapor. I haven't been able to get a
close look at the driver so I can't tell where it is made or if there is a
product name or manufacturer. They will sell that part of it for $150!
An ultrasonic cleaner contains a power oscillator driving a large piezoelectric
transducer under the cleaning tank. Depending on capacity, these can be quite
massive.
A typical circuit is shown below. This is from a Branson Model 41-4000 which
is typical of a small consumer grade unit.
Two windings on the transformer (T1, which is wound on a toroidal ferrite
core) provide drive (D) and feedback (F) respectively. L1 along with the
inherent capacitance of PT1 tunes the output circuit for maximum amplitude.
The output of this (and similar units) are bursts of high frequency (10s to
100s of kHz) acoustic waves at a 60 Hz repetition rate. The characteristic
sound these ultrasonic cleaners make during operation is due to the effects
of the bursts occuring at 60 Hz since you cannot actually hear the ultrasonic
frequencies they use.
The frequency of the ultrasound is approximately 80 kHz for this unit with a
maximum amplitude of about 460 VAC RMS (1,300 V p-p) for a 115 VAC input.
WARNING: Do not run the device with an empty tank since it expects to have
a proper load. Do not touch the bottom of the tank and avoid putting your
paws into the cleaning solution while the power is on. I don't know what,
if any, long term effects there may be but it isn't worth taking chances.
The effects definitely feel strange.
Where the device doesn't oscillate (it appears as dead as a door-nail), first
check for obvious failures such as bad connections and cracked, scorched, or
obliterated parts.
To get inside probably requires removing the bottom cover (after pulling the
plug and disposing of the cleaning solution!).
CAUTION: Confirm that all large capacitors are discharged before touching
anything inside!
The semiconductors (Q1, D1, D2, D3) can be tested for shorts with a multimeter
(see the document: Basic Testing of Semiconductor
Devices.
The transformer (T1) or inductor (L1) could have internal short circuits
preventing proper operation and/or blowing other parts due to excessive load
but this isn't kind of failure likely as you might think. However, where all
the other parts test good but the cleaning action appears weak without any
overheating, a L1 could be defective (open or other bad connections) detuning
the output circuit.
Where the transistor and/or fuse has blown, look for a visible burn mark on
the transducer and/or test it (after disconnecting) with a multimeter. If
there is a mark or your test shows anything less than infinite resistance,
there may have been punch-through of the dielectric between the two plates.
I don't know whether this could be caused by running the unit with nothing in
the tank but it might be possible. If the damage is localized, you may be able
to isolate the area of the hole by removing the metal electrode layer
surrounding it to provide an insulating region 1/4 inch in diameter. This
will change the resonant frequency of the output circuit a small amount but
hopefully not enough to matter. You have nothing to lose since replacing the
transducer is likely not worth it (and perhaps not even possible since it is
probably solidly bonded to the bottom of the tank).
When testing, use a series light bulb to prevent the power transistor from
blowing should there be a short circuit somewhere (see the document:
Troubleshooting and Repair of Consumer Electronic
Equipment) AND do not run the unit with and empty tank.
Here are some comments on ultrasonic cleaner repair. These would appear to be
more for larger units but some of the info should apply to the small ones
as well:
(From: B. Clark (bclarkson@primary.net).)
I spend a great deal of time repairing ultrasonic generators from sinks in
medical use. I can tell you this. While different manufacturers use
different circuits, the basic design is the same everywhere. The most
common failure mode is that the switching transistor(s) are shorted. When
this happens, does the fuse blow in your case? If this is true, replace
the rectifier bridge. If the circuit contains extra diodes, check those
for shorts as well. Always replace both transistors at the same time.
You can use ECG/NTE equivalents, so long as both are the same - don't
count on a new 2N6308 and an ECG283 working together in this case.
Assuming the fuse never blows and the output frequency is around 40 to 50 khz,
that rules out most of the small caps and resistors. Most generators that I
have worked on produce a wave around 45 khz. A bad cap or resistor would
cause it to be off frequency. The transducers should test as open. If they
test as anything other than open on an multimeter (after allowing for settling
as they are sensitive to vibration), then they could be bad. Transducer
failure in my experience is not that common. It may suggest that your
customer has been running the unit with the tank empty or only partially full.
The circuit is tuned. 100% of all generators sent to me have one or
more shorted transistors. The customer complaint is usually "No
ultrasonic action" or "Weak ultrasonic action". 99.999% of the time,
using an ohmmeter and replacing shorted semiconductors corrects the
problem. I have had one unit where a precision cap was out of tolerance
and detuned the circuit. One nearby hospital has sent in three 500 watt
units that were ran without the transducers connected. In all cases, the
fuse didn't blow, however each of the three caught on fire. One of these
has a 1/8 in hole through a coil in the transformer.
If any part drifts out of tolerance, the transistor will short. I have
seen perfectly fine circuits short switching transistors when the unit is
ran with no water in the tank. Do not attempt to run with one
transducer. You will meet with failure. You should attempt to replace
with the exact oem part when available. If you cannot find the original
and have determined a adequate substitute, replace both of them.
I keep mentioning transistors realizing that small units have only one. The
units I work on have 4 to help generate 500 watts of power.
(From: Lance Edmonds (lanceedmonds@xtra.co.nz).)
Essentially, a fog machine consists of a heater unit and a pump, plus
electronics to control the heater temperature, and control how much fog juice
is pumped through the heater.
Most common failures are severed remote control leads, burned out pumps, or
heating unit blockages.
I've never seen one with a fan, but many folks use a fan to disperse the fog
to the desired locations across a stage, etc.
Unlike dry-ice, fog from a "fogger" rises and disperses quite quickly unless
there is no ventilation... you can add some perfume (a few drops to the large
tank) to reduce the "flavor" of the fog... when it's thick it tastes and
smells horrid!
(From: krbjmpr@hotmail.com)
I have examined a couple machines just out of personal curiosity. what I
found was, and keep in kind that these were the lower end series, was
basically a high power heater and a small fluid pump.
From what I have seen , and can deduce, is that a high wattage heater block
constantly is heating a 'transition' tube. Temperature is unknown, but it
is damn hot. Temperature was controlled by a simple bimetal strip that looks
like it activated a triac or similar device. Heater power was supplied by
the triac. The fog fluid was pumped from the reservoir by a small fluid pump
that ran on 6 to 12 VDC. The amount of fog produced was controlled by a large
rheostat that had 12 volts applied to it, thereby creating a variable voltage
divider. Activation of the 12 volts to the pump for fog was through a small
relay that was able to be activated either through a switch added to the fog
machine that completed a circuit, or the machine was set on a timer
(internal) for fixed interval. Switch voltage was also 12 volts. Fog fluid
was injected into the transition tube, and the output nozzle was
significantly larger than the input. Estimated age of the machines was about
14 years or so.
After I saw the insides of these things, I am amazed that they are able to
demand $300 to $400 price tags. I am thinking about making one of these out of
a water-cooled resistor and gravity feeding a gallon jug of the juice through
an older 24 VAC sprinkler valve. One of those rainy day projects.
From: don@Misty.com (Don Klipstein)
I once fixed a "Ness" brand "Mini-Fogger". Turned out there was a
broken solder joint where the jack for the plug-in "remote" button went
into a circuit board.
Also sometimes, the pump sticks. Tapping the pump with a screwdriver
while attempting to run it may unstick it.
This thing is simple enough and made of parts that are reliable enough,
with the possible exception of the pump. I would mostly look for broken
connections or bad solder joints or clogs.
There is supposed to be a cutoff (float) switch to stop the dehumidifier
when the container is full. Hopefully, it works (and you didn't neglect
to install it when the unit was new!)
Common problems with these units are often related to the fan, humidistat,
or just plain dirt - which tends to collect on the cooling coils. The
sealed refrigeration system is generally quite reliable and will never need
attention.
An annual cleaning of the coils with a soft brush and a damp cloth is a good
idea. If the fan has lubrication holes, a couple of drops (but no more) of
electric motor oil should be added at the same time.
The fan uses an induction motor - shaded pole probably - and may require
cleaning and lubrication. See the section: Problems
with induction motors.
The humidistat may develop dirty or worn contacts or the humidity sensing
material - sort of like a hot dog wrapper - may break. If you don't hear
a click while rotating the control through its entire range, this may have
happened. If you hear the click - and the dehumidifier is plugged into
a live outlet - but nothing happens, then there is probably a problem in
the wiring. If just the fan turns on but not the compressor, (and you have
waited at least 5 minutes for the internal pressures to equalize after
stopping the unit) then there may be a problem with the compressor or its
starting relay (especially if the lights dim indicating a high current).
A very low line voltage condition could also prevent a refrigeration system
from starting or result in overheating and cycling. A sluggish slow rotating
or seized fan, or excessive dirt buildup may also lead to overheating and
short cycling.
A unit that ices up may simply be running when it is too cold (and you don't
really need it anyway). Dehumidifiers may include sensors to detect ice
buildup and/or shut off if the temperature drops below about 60 degrees F.
Common problems with garbage disposals relate to three areas:
The red reset button is a circuit breaker. Either the motor is drawing
too much current due to a shorted winding or a tight bearing or the breaker
is faulty. Without an ammeter, it will be tough to determine which it
is unless the rotor is obviously too tight.
If you have a clamp-on ammeter, the current while the motor is running
should be less than the nameplate value (startup will be higher). If
it is too high, than there is likely a problem with the motor. As an
alternate you could try bypassing the circuit breaker with a slow blow
fuse of the same rating as the breaker (it hopefully will be marked) or
a replacement breaker (from another dead garbage disposal!. If this
allows the disposer to run continuously your original little circuit
breaker is bad. These should be replaceable.
If the bearings are tight, it is probably not worth fixing unless it is
due to something stuck between the grinding disk and the base. Attempting
to disassemble the entire unit is likely to result in a leak at the top
bearing though with care, it is possible to do this successfully.
"I have an ISE In-Sink-Erator (tm), Badger I model. I tried turning mine on a
few minutes ago, the motor started then stopped and now nothing happens when I
flip the wall switch, not even a click."
Of course, first make sure there is nothing jamming it - use a flashlight
to inspect for bits of bone, peach pits, china, glass, metal, etc. Even a
tiny piece - pea size - can get stuck between the rotating disk and the
shredder ring. WITH THE DISPOSAL UNPLUGGED OR THE BREAKER OFF, work the
the rotor back and forth using the hex wrench that came with the unit or
a replacement (if your unit is of the type that accepts a wrench from below.
If it is not of this type, use the infamous broom handle from above.)
The internal circuit breaker will trip to protect the motor if the rotor
doesn't turn. Turn off the wall switch, wait a few minutes for the circuit
breaker and motor to cool, and then press the red reset button underneath
the disposal. If it does not stay in, then you didn't wait long enough or
the circuit breaker itself is defective. Then, turn on the water and try
the wall switch again (in-sink switch if it is a batch feed model).
Assuming it is still tight with nothing stuck inside and/or jams repeatedly:
(From: Rob-L (rob-l@superlink.net).)
That's about how long it takes for the nut to rust away on the shredder
disc of Insinkerator/Sears units. My comments will address ISE/Sears
deluxe models with the stainless disc, for those who might have one.
When the nut/washer rusts away, the disc will wobble and get jammed. With
the power off, try to rock the disc inside the unit. You might need to
wiggle the motor shaft with a 1/4" hex wrench under the unit.
If you can free things up, and the disc can be rocked, it's the
nut/washer. When that goes, so does the gasket, and unfortunately it
requires total disassembly of the grinding chamber to replace the little
gasket, because the disc will not come out otherwise. And if you don't
replace the gasket, water/gunk will run down the motor shaft and into the
motor. When those units go, you're better off to get a new disposer.
I think they intentionally use a non-stainless steel nut, because
otherwise the units would last a long time. Even the replacement nuts
will corrode. The motor shaft will also corrode, but not as fast as the
nut. With a stainless shaft and nut/washer, the disposer would give many
more years of service. And that's why they don't make 'em that way. :)
One part that is worth replacing is the mounting gasket. It's the part
with the flaps that you feed things through. It gets cut-up and damaged
by chlorine from sink cleaning or dishwasher discharge. (brittle, rough)
It's a $4 part, usually available at Home Depot next to the new disposers,
and it slips on in a matter of minutes -- you just disconnect the trap,
then drop the disposer down by undoing the retaining ring. Swap the
gasket, re-attach things, and your sink drain looks brand new.
By the time the leak is detected, it is probably too late to save the
disposal as corrosion of the steel shaft, excessive wear of the bronze
bushing, as well as possible electrical damage has already occurred.
Realistically, there is nothing that could have likely been done in any
case. It is virtually impossible to repack such a bearing in such a way
to assure that a leak will not develop in the near future.
If your previous garbage disposal was an ISE In-Sinkerator or Sears, then
replacement is usually a 10 minute job if the under-sink plumbing is in
reasonably good condition (doesn't crumble to dust when you touch it).
If the part that mounts to the sink is not corroded and not leaking, I
just leave it alone. The only tools required are a screwdriver and wire
strippers (possibly) to move the power cord or cable to the new unit and
a screwdriver or socket driver and a large adjustable wrench or pliers to
unscrew the drain pipe and dishwasher connection (if used). Complete
instructions should be provided with the replacement unit.
These motors are quite reliable but the bearing can rot/rust/sieze at
the base where it may be under water or at least in a humid environment.
The casing may leak at the bearing (if not magnetically coupled) or at the
wire connections. Repair of these motors is probably not worth the effort.
Three types of automatic switches are commonly used:
(From: Pete Peterson (peterson@usaor.net).)
I've repaired a couple with the same problem and its been the motor driver
transistors each time. There are two or three direct coupled transistors
from each side of the motor (probably equates to an H bridge) and one or
all of these go open. Probably under designed for the current they carry.
Just trace the wires from the motor out through the circuit and check the
first several transistors you come to.
Parts of a typical garage door operator (chain drive). Details may differ
on operators with worm screw or other drive schemes.
On units with DIP switches, both transmitter and receiver settings must
match exactly. In addition, for older units in particular, the contacts
on the switches may be dirty and/or oxidized so flipping each switch back
and forth a few times may be needed to make a reliable connection. I have
also seen a situation where one bit wouldn't work in one position - the
other position was fine.
Are there such things as IR remote controls for garage door openers
instead of the usual radio frequency variety?
For many types (Sears, Genie, etc.), there is a thermally operated
time delay consisting of a coil of resistance wire, a bimetal strip,
and a set of contacts. When the operator is activated, power is applied
to the heater which causes the bimetal strip to bend and close the
contacts turning on the light. Due to the mass of the bimetal strip,
it takes a couple of minutes to cool down and this keeps the light on.
The most common failure is for the fine wire in the heater to break at
some point. If you can locate the break, it may be repairable at least
as a temporary solution. You cannot solder it, however, so a tiny
nut and bolt or crimp will be needed. However, sticking contacts resulting
in a light that does not always go off are also possible. Cleaning the
contacts may help.
This part is very easily accessed once the sheetmetal cover is removed.
It is probably somewhere in the middle of the unit fastened with three
screws. Just remember to unplug the operator first!
Depending on the manufacturer, the original part may be available. I
know that it is for Sears models.
You could also use a time delay relay or a solid state circuit (RC delay
controlling a triac, for example) but an exact replacement should be just
a whole lot less hassle.
When it gets to the end of the track - be it at the top or bottom, there
must be something that it trips to shut down the motor. At the same time,
this is supposed to set things up so that the next activation will reverse
the door.
Does the door stop and shut off when it reaches the end or does it eventually
just give up and trip on the safety?
When it trips the switch to stop at the end of its travel, some mechanism
is toggled to change the 'state' of the door logic so that it knows to
go up the next time it is activated. It is probably this device - be it a
latching relay, mechanical two position switch, or a logic flip flop - that
is not being properly toggled.
I would recommend attempting to determine what device that switch is actually
supposed to toggle - it probably is in the operator unit itself (not the
control box).
First compare the antennas on the two remotes. If they are the same and
there are no broken connections, your problem lies elsewhere. The chance
of the wire itself being bad is pretty slim.
It could also be that the receiver and transmitter frequencies are not quite
identical. If the remote units have been abused, this is more likely. I
don't know about Genie but my (old) Sears has trimmers and I was able to
adjust it *very* slightly to match that of the receiver and boost sensitivity.
CAUTION: If you try this (1) mark the exact position where it was
originally and (2) do it only on the transmitter that has the problem. This
will minimize the possibility of shifting the frequency to where it might
interfere with other devices. See the section: Adjusting
garage door operator remote unit for more information.
It should not work at all if the switches are set improperly. In such a
case, first test and/or replace the battery. If this does not help, check
the switch settings.
The tuning is done via a variable capacitor trimmer (probably).
There will probably be a trimmer inside the hand unit (don't touch the one
in the receiver). Position yourself at a reasonable distance and use a
plastic tool to adjust it until the door operates while holding the button
down. The door will respond at increasing distances as you approach the
optimal setting.
Note: mark the original position first in case this has no effect!
This assumes there is an adjustment - if there is none, you may have an
actual electronic failure, bad connections, etc.
(From: Kirk Kerekes (redgate@tulsa.oklahoma.net).)
Go to a home center, and wander over to the garage door openers. Nearby,
you will find GDO accessories, and among the accessories will be a universal
replacement remote kit that includes a receiver, a transmitter and possibly
a power supply. For about $40, you can by and install the receiver in place of
the existing receiver. If your home center carries Genie openers, you can even
get an Intellicode add-on unit that uses Genie's scanner-proof code-hopping
technology.
Increasing the safety override force settings may help but are not a wise
solution as the door will then be more of a hazard to any legitimate
obstructions like people and pets.
Another possibility is that the motor start/run capacitor has weakened
and is not permitting the motor to provide the proper torque. You can
test the capacitor if you have a DMM with a capacitance scale or LCR meter.
Better yet, just replace it.
Chamberlain tech support told me they suggest I buy a whole new unit. Is
there any other way to make my door usable with a different remote, or
some other arrangement?"
(From: Panayiotis Panayi (panikos@mishka.win-uk.net).)
Which Chamberlain operator is it, i.e., which model number. You can
buy the handsets for Chamberlain operators up to 5 years old. If it
is older you will have to buy a new Rx & Tx for it. Most operators
have three screw terminals on the back for the attachment of Rxs.
The old Chamberlain operators conformed to this. The new ones have
the Rx built onto the main PCB inside the operator and have 4
screws externally for pushbuttons and infra red safety beams. If
yours has 4 screws you will have to provide a separate PSU for the
new Rx or solder two pieces of wire after the step down
transformer on the PCB. You must do it before the rectifiers.
Otherwise the current drain from the Rx will be too big for them.
Besides almost all modern separate Rxs take 24 VAC.
If there is access to your house from the garage, this security is even more
critical. Once inside the garage, a burglar can work in privacy at their
leisure - and a nice set of tools is probably there for their convenience
in getting through your inside door! Filling up a good sized car or truck
with loot - again in complete privacy - drive out and close the door behind.
No one will be the wiser until you get back.
All of the switches for a given location (i.e., inside and outside the storm
door) are wired in parallel. There will be three terminals on the chimes
unit - Common (C), Front (F), and Back or Rear (B or R). This notation may
differ slightly for your unit. Typical wiring is shown below. An optional
second chimes unit is shown (e.g., in the basement or master bedroom - more
can be added in parallel as long as the bell transformer had an adequate VA
rating.)
Most 'not-chiming' problems are due to the one or more of the following:
Note: where multiple switches operate the chimes from similar locations,
multiple wires may be connected to each switch terminal. Don' mix these up
or lose them inside the wall!
If just a single location doesn't work, that should narrows down the problem.
If only one switch does not work, first test the switch. If disconnecting
the wires from the switch does not result in full transformer voltage across
the wires, then there is a bad connection between you and the transformer,
the transformer has no power, is defective, or there is a short circuit
somewhere.
Note: due to coupling between the wires, there may be some voltage across
all combinations. The most will be across the relevant one (and this will
be the only combination that will sound the chimes if you are using them
as a voltage indicator).
A quick test to determine if the transformer is being powered is to
feel it! The transformer should be warm but not hot to the touch. If
it is stone cold, either there is no power or a bad connection in the
input line) circuit.
Test for voltage between the Common and Front or Back terminals when the
appropriate button is pressed.
The only concern is whether the existing transformer that operates the
chimes has enough capacity - you may need to replace it with one with a
higher 'VA' rating (the voltage rating should be the same). These are
readily available at hardware and electrical supply stores and home
centers.
Some people might suggest just paralleling an additional transformer across
the original one (which may be possible if the output phases match). I
would really recommend simply replacing it. (This is probably easier
mechanically in any case.) Unless the transformers output voltages as
designed are identical, there will be some current flowing around the
secondaries at all the times. At the very least, this will waste power
($$) though overheating is a possibility as well.
However, since the 'Y' outputs of the transformers are connected at all
times to the 'C' terminals of the of the chimes units AND the 'X' outputs
are tied together, any voltage difference between the 'Y' outputs will
result in current flow through the chimes coils even if no button is
pressed. Thus, the transformers must be phased such that there is no (or
very little) voltage between 'Y' outputs. Test between 'Y' outputs with a
multimeter set on AC Volts after you have the transformers powered: if you
measure about double the transformer voltage rating (e.g., 32 VAC), swap
ONE set of transformer leads (input or output but not both) and test again.
If it is still more than a couple volts, your transformers are not matched
well enough and you should purchase identical transformers or use the
approach in (1), above.
Another button can be added in parallel with any of the existing ones (i.e.,
between points X and F or X and B in the diagram). The only restriction is
that you may not be able to have more than one lighted button in each group
as the current passing through the lighted bulbs may be enough to sound the
chimes - at least weakly.
If you cannot trace the wiring (it is buried inside the wall or ceiling)
the only unknown is which side of the transformer to use. If you pick the
wrong one, nothing will happen when you press the button.
The bell or chimes portion may be either an electromechanical type - a coil
forming an electromagnet which pulls in a plunger to strike a gong or bell.
See the section: Electromechanical doorbells and chimes.
Others are fully electronic synthesizing an appropriate tone, series of tones,
or even a complete tune on demand. Repair of the electronics is beyond the
scope of this document. However, there are several simple things that can
be done:
First, remove the batteries or kill power to all transmitters and wait see if
the problem still occurs.
A common type of motor that may be used in these is a small AC split phase or
capacitor run induction motor. The relative phase of the main and phase coils
determines the direction. These probably run on 115 VAC. A capacitor may
also be required in series with one of the windings. If the antenna does not
turn, a bad capacitor or open winding on the motor is possible. See the
chapter: Motors 101 for more info on repair of these
types of motors.
The base unit is linked to the motor unit in such a way that the motor
windings are powered with the appropriate phase relationship to turn the
antenna based on the position of the direction control knob. This may
be mechanical - just a set of switch contacts - or electronic - IR detectors,
simple optical encoder, etc.
Here is some info on connections for some types:
(From: Will Shears (wshearsN@wyzz.sbgnet.com).)
The rotor is operated on 24 volts AC. The wires are used like this:
OR, the third lead was a meter lead, and the rotor turned a pot that changed
the meter reading according to the position of the pots' turning. The rest is
the same.
Inside the box was a 70 uF, 50 V or so NON POLARISED capacitor, or an AC
capacitor. Usually the capacitor was connected across the #2 and #3 lead. It
provided a phase shift for the motor, and you put 24 volts from #1 to #2 for
forward, and to #1 and #3 for reverse. The other lead will either pulse as the
rotor turns, or the voltage will change between the #1 & #4 lead, assuming
there is a load resistor across the terminals. I would try a 470 ohm 1 watt
resistor to start, and probably a 100 to 200 will be right. If you have a
VOM, check for resistance across 1 and 4, if you get some, not a short, it is
the second type, if you get a short or open, it is a pulse type.
(From: Al Cunniff (acunniff@erols.com).)
Here is one place that is devoted to antenna rotors if you give up:
Note: They don't have email built into their site, but the site tells you just
about everything else you need to know about their business and service. It
has a good rotor FAQ section too.
I'm not connected in any way with Norm's,
See the sections on these types of motors for more details than the following
summaries provide.
A single or multiple stage gear reducer drops the relatively high speed
at which these motors are most efficient to whatever the tool actually
requires, increasing the torque as well.
Universal motors can also be speed controlled relatively easily using a
variant of a simple light dimmer type circuit. Excellent torque is
maintained over a very wide range extending to nearly 0 RPM.
Speed control is easily accomplished by low cost electronic circuits which
chop the power (pulse width modulation) rather than simply using a rheostat.
This is much more efficient - extremely important with any battery operated
device.
For example, a typical drill press may have one or two sets of stepped
pulleys providing 3 to 15 or more speeds by changing belt positions. A
continuously variable cone drive is also available as an option on some
models. This is extremely convenient but does add cost and is usually not
found on less expensive models.
An internal thermal overload protector may be incorporated into larger
motors. WARNING: this may be self resetting. If the tool stops on its own,
switch off and unplug it before attempting to determine the cause.
Generally, these induction motors are virtually maintenance-free though
cleaning, tensioning, and lubrication may be required of the drive system.
However, electronic speed control of induction motors, while possible,
is relatively complex and expensive requiring a variable frequency
variable voltage power supply. Therefore, universal motors may be used
on stationary tools like scroll saws with continuously variable electronic
speed control.
As technology marches on, there will be increasing use of electronically
controlled motors in all sorts of appliances and power tools. Greatly
increased efficiency and finer control are possible by using 3 phase
permanent magnet motors - similar to larger versions of brushless DC fan
motors - with integrated power control electronics. But, for these
applications, that is largely in the future (currently: Spring 2000).
As with over-the-counter drugs, extra strength does not necessarily translate
into faster relief, higher current does not always mean better performance,
and horsepower ratings much above what you would compute from V x A may be
more of a marketing gimmick than anything really beneficial.
Newer ones have the grounded cordset while the newest 'double insulated
tools' are of mostly plastic construction and are back to a 2 wire ungrounded
cord.
As with any electrical appliances, inspect cords regularly and repair or
replace any that are seriously damaged - if the inner wiring is showing,
nicked, or cut; if the plug is broken or gets hot during use, or where
the cord is pulled from or broken at the strain relief.
Typical problems include:
Electric toothbrushes
These are basically similar to any other small battery operated appliance or
tool such as a screwdriver or drill. The permanent magnet motor runs off of
rechargeable NiCd batteries and cause the bristles or whatever to oscillate,
rotate, or vibrate. Interchangeable 'brush' units allow each member of the
family to have their own. Coupling to the internal battery is often via a
'contactless' mechanism using a pair of coils to transfer AC inductively.
Inside the hand unit, this is rectified to charge the NiCd (usually) battery.
See the section: Inductively coupled charging circuit
for an example of one such design.
Inductively coupled charging circuit
This was found in an Interplak Model PB-12 electric toothbrush but similar
designs are used in other appliances that need to be as tightly sealed as
possible.
E1 CR2 R1 E3
AC o----+----+--|>|-----+---/\/\---+----+----------------+-------+ Coupling
| ~| CR1 |+ 1K | | | ) Coil
+-+-+ +--|<|--+ | | / R2 | ) 200T
RU1 |MOV| CR3 | | C1 _|_ \ 390K | ) #30
+-+-+ +--|>|--|--+ .01uF --- / CR5 | E4 ) 1-1/2"
E2 | | CR4 | 250V | \ MPSA +---|<|---|----+--+
AC o----+----+--|<|--+ | | 44 | | |
~ |- R3 | | Q1 |/ C C3 _|_ _|_ C2
+-----/\/\----+----+----| .1uF --- --- .0033uF
CR1-CR4: 1N4005 | 15K |\ E 250V | | 250V
| R4 | | |
+---------------/\/\------+---------+----+
1K
The battery charger is nothing more than a diode to rectifier the signal
coupled from the charging base. Thus, the battery is on constant trickle
charge as long as the hand unit is set in the base. The battery pack is a
pair of AA NiCd cells, probably about 500 mA-h.
S1B
S1A +--o->o
D1 _|_ | R1,15,2W
+---|>|---+------o o--+ L o---/\/\---+
Coupling | | R2,10,2W |
Coil + _|_ BT1 M o---/\/\---+
120T ( _ 2.4V |
#30 ( ___ .5A-h H o----------+
13/16" + _ |
| | +-------+ |
+---------+--------| Motor |-----------+
+-------+
Braun electric toothbrush repair
(From: David DiGiacomo (dd@Adobe.com).)
Hand massagers
These are simply motors with an off-axis (eccentric) weight or electromagnetic
vibrators. If the unit appears dead, check the plug, cord, on/off switch,
internal wiring, and motor for continuity. Confirm that the mechanical parts
turn or move freely.
Hair dryers and blow dryers
A heating element - usually of the NiChrome coil variety - is combined with
a multispeed centrifugal blower.
The Ground Fault Circuit Killer (GFCK)
Note: I have heard that the official name for these disasters is: Appliance
Leakage Circuit Interrupter (ALCI). I like mine better. :)
<------------------------ Plug ---------------------->|<- Cord ->
___ :
Plug (H) <---o o---+-----------------------------------------------o H
CB1* | ===== R1* :
+-----^^^^^-------/\/\-------------+-------+ :
| L1 | | :
| 120 T, #26, 3 layers Q1 __|__ | :
| .1"x1" ferrite core T34557 _\_/_ | :
| / | | :
MDC +--+--+ +-----+------+------+----' | C2 _|_ :
Z251 | MOV | | | | | | .1uF --- :
+--+--+ | / | | | 250V | :
| | R2 \ C1 _|_ D1 _|_ | | :
| | 300 / .22 --- /_\ | | :
| | \ uF | | | | :
| | | | | | | :
+------|-----+------+------+-------+-------+ :
___ | | 1N4004 :
Plug (N) <---o o---+---------------------------------------------------o N
CB2* | R3 1K :
+--------------/\/\-------------------------o G
:
* R1 is positioned to hold the latch for CB1 and CB2 in place until it
vanishes in a puff of smoke. It is interesting to note that R1 is NOT
a flameproof resistor - it looks like an ordinary 1/8 W carbon composition
type.
Curling irons
These are just a sealed heating element, switch, and thermal protector
(probably). Check for bad connections or a bad cord or plug if there is
not heat. A failed thermal protector may mean other problems. While
these are heating appliances, the power is small so failures due to
high current usually do not occur.
VCR cassette rewinders
Cassette rewinders typically consist of a low voltage motor powered from
a built in transformer or wall adapter, a belt, a couple of reels, and some
means of stopping the motor and popping the lid when the tape is fully
rewound.
Vacuum cleaners, electric brooms. and line powered hand vacs
Despite all the hype surrounding vacuum cleaner sales, there isn't much
difference in the basic principles of operation between a $50 and $1,500
model - and the cheaper one may actually work better.
Vacuum cleaner mechanical problems
Vacuum cleaner electrical problems
>
Vacuum cleaner hose damage
"We have been quoted a price of $100 to replace the hose on our Panasonic
(Mc-9537) vacuum cleaner. It has a rip in it; next to the plastic housing
where the metal tubing starts. Does anyone know if there is a more
economical way to solve this problem?"
High tech vacuum cleaners?
Excerpt from a recent NASA Tech Brief:
"The Kirby Company of Cleveland, OH is working to apply NASA technology to
its line of vacuum cleaners. Kirby is researching advanced operational
concepts such as particle flow behavior and vibration, which are critical
to vacuum cleaner performance. Nozzle tests using what is called Stereo
Imaging Velocity will allow researchers to accurately characterize fluid
and air experiments. Kirby is also using holography equipment to study
vibration modes of jet engine fans."
Dustbusters(tm) and other battery powered hand vacs
These relatively low suction battery powered hand vacuums have caught on
due to their convenience - certainly not their stellar cleaning ability!
Dustbusters left on continuous charge and battery problems
The low current trickle charger supplied with these battery operated hand-vacs
allow Dustbusters and similar products to be be left on continuous charge so
long as they are then not allowed to self discharge totally (left on a shelf
unplugged for a long time). Older ones, in particular, may develop shorted
cells if allowed to totally discharge. I have one which I picked up at a
garage sale where I had to zap cells to clear a shorts. However, it has been
fine for several years now being on continuous charge - only removed when used.
Floor polishers
A relatively large universal motor powers a set of counter-rotating
padded wheels. Only electrical parts to fail: plug, cord, power switch,
motor. Gears, shafts, and other mechanical parts may break.
Heating pads
Heating pads are simply a very fine wire heating element covered in thick
insulation and then sealed inside a waterproof flexible plastic cover.
Internal thermostats prevent overheating and regulate the temperature.
The hand control usually provides 3 heat settings by switching in different
sections of the heating element and/or just selecting which thermostat is used.
Electric blankets
As with heating pads, the only serviceable parts are the controller and
cordset. The blanket itself is effectively sealed against any repair
so that any damage that might impact safety will necessitate replacement.
Humidifiers
There are three common types:
Ultrasonic humidifiers
(From: Filip "I'll buy a vowel" Gieszczykiewicz (filipg@repairfaq.org).)
Ultrasonic waterfalls?
I don't suppose you are likely to encounter these but if you do, servicing
procedures will be similar to those described in the section:
Ultrasonic humidifiers.
Ultrasonic cleaners
Ultrasonic cleaning is a means of removing dirt and surface contamination from
intricate and/or delicate parts using powerful high frequency sound waves in
a liquid (water/detergent/solvent) bath.
R1 D1
H o------/\/\-------|>|----------+
1, 1/2 W EDA456 |
C1 D2 |
+----||----+----|>|-----+
| .1 uF | EDA456 | 2
| 200 V | +-----+---+ T1 +---+------->>------+
| R2 | _|_ C2 ):: o 4 | | |
+---/\/\---+ --- .8 uF D ):: +----+ | |
| 22K _|_ 200 V )::( + |
| 1 W - 1 o )::( ):: _|_
+-----------------+---------+ ::( O ):: L1 _x_ PT1
| R3 | 7 ::( ):: |
| +---/\/\---+ +-----+ ::( 5 + |
C \| | 10K, 1 W | F ):: +---+ | |
Q1 |--+-+--------------+ 6 o ):: | | |
E /| | D3 R4 +---+ +----+------->>------+
| +--|<|---/\/\--+ _|_
| 47, 1 W | --- Input: 115 VAC, 50/60 Hz
| | | Output: 460 VAC, pulsed 80 kHz
N o------+-------------------+---+
The power transistor (Q1) and its associated components form an self excited
driver for the piezo-transducer (PT1). I do not have specs on Q1 but based on
the circuit, it probably has a Vceo rating of at least 500 V and power rating
of at least 50 W.
Fog machines
If you don't know what a fog machine does, you probably don't need to read
this section!
Dehumidifiers
Electric dehumidifiers use a refrigeration system to cool a set of coils
which condenses water vapor. The heat is then returned to the air and
it is returned back to the room. On the surface, this seems like an
incredible waste of energy - cooling the air and heating it back up -
but it is very effective at removing moisture. A typical large dehumidifier
will condense something like 30 pints in 24 hours - which, unless you have
it located over a drain - then needs to be dumped by hand.
Garbage disposals
A garbage disposal is just an AC induction motor driving a set of centrifugal
hammers (they use to use sharp cutters but these were even more dangerous).
The cutters throw the food against an outer ring with relatively sharp slots
which break up the food into particles that can be handled (hopefully) by
the waste system. However, always use generous amounts of cold water (which
helps to cool the motor as well) and let it run for a while after there is
nothing left in the disposal and it has quieted down. This will assure a
trouble free drain. Otherwise, you may be inviting your friendly plumber
over for a visit!
Unless you are the truly die-hard doit-yourselfer, repair of disposals is
probably not a good use of your time. The ultimate reliability of all
but the most obvious and simple repairs is usually unknown and could be
very short. However, other than time, there is nothing to be lost by
at least investigating the source of the problem.
Garbage disposal pops reset button but nothing blocked
Even if nothing is stuck in it, is the rotor free - not too tight? If you
have that little wrench that comes with many disposers, you should be able
to turn the rotor relatively easily (I would say about 1 foot-pound of
torque or less if your arm is calibrated). A tight bearing may be the
result of a shaft seal leak - see the next section:
Garbage disposal seizes repeatedly.
Garbage disposal is stuck - hums but does not turn
Here are typical problems:
"I need help. Our garbage disposal is stuck. It hums but doesn't turn. If I
leave it on for more than a few seconds it trips the circuit breaker on the
unit. Any tips on how to solve this shy of buying a new unit? The unit is 7
years old."
Garbage disposal seizes repeatedly
A garbage disposal that doesn't have anything stuck in the cutting chamber
but seems to be hard to turn or will work with effort until left alone for
a day or two probably has a bad bearing caused by a leak at the shaft seal.
Of course, water gushing out of the lower part of the disposal (or *any*
amount of water dripping from inside the motor housing) is one indication
that there is a leak! This also represents a safety hazard so the disposal
should be left unplugged and not be used even if it still runs.
Garbage disposal replacement (or upgrade)
My general recommendation is to get the approximately $100 1/2-3/4 Hp Sears
(ISE In-Sinkerator(tm) manufactured) unit when it is on sale (which is about
every week). These now have at least a 4 year warranty.
Sump pumps and utility pumps
Sump pumps come in two major varieties:
Utility pumps are often of the submersible variety.
Most common problems are with switches that are no longer reliable or totally
broken. Universal replacements are generally available since the switch is
not usually an integral part of the motor/pump unit.
Toys
Since there are a semiinfinite number of variations on electrically powered
toys, the only comment I have is that these are almost always combinations
of small PM motors, switches, batteries, light bulbs - and totally impossible
to identify electronic components. With small kids, physical destruction is
probably a much more common occurrence than a part failure!
Incorrect response for remote control toys
The following may apply when there is no response or an uncontrolled response
for certain commands like turn left or move backwards:
Garage door operators
Typical garage door operators use a 1/3 to 3/4 horsepower induction motor
with a belt drive chain or screw mechanism to move the 'trolley' that actually
grabs the door. A switch or pair of switches activated at each end of travel
stops the motor and toggles the state (up or down) of the controller. Door
blockage sensors detect obstructions and stop or reverse travel. A light
turns on with motor start and stays on for 3-5 minutes thereafter, controlled
by a simple timer.
General garage door operator problems
Garage door operator light does not work correctly
Assuming the unit otherwise operates normally and you have tried replacing
the light bulb(s):
Garage door operator loses track of where it is
You press the button to close the door and it works fine. However, next
time you press the button to make the door go up and it tries to go down into
the ground.
Garage door remotes behave differently
"I've got 2 Genie garage door remotes. One of them works from about 100 yards
away; the other I almost have to be right next to receiver. I suspect that
the antenna is the problem; either too short, or blocked by something."
Adjusting garage door operator remote unit
This situation may arise if one hand unit operates normally but the other
has a very short range. If you have only one hand unit, it might also be
the problem though not likely to have just happened on its own - either
it was improperly set up at the factory (if new) or hand unit was dropped
once too often.
Improving sensitivity of garage door openers receivers
Where a garage is constructed with aluminum siding, the remote signal may
be significantly attenuated and of insufficient strength to activate the
receiver module (inside the garage) of the opener at any useful distance
or at all. Assuming the system operates normally otherwise (i.e., activation
is normal with the door open), two approaches (either or both together) can
be taken to solve this problem:
Universal remote/receiver units for garage door operators
So you lost your garage door remote or it got run over by your 4x4 :-). Or,
it just expired due to age. There are alternatives other than an entire new
operator if the remote is no longer available:
Garage door operator doesn't work reliably in cold weather
First, check the lubrication. The most common problem is likely to be
gummed up grease in the chain drive (if used) or the bearings of the
rollers. Note: the track itself generally doesn't require lubrication.
Chamberland garage door opener repair?
"My remote broke for my very old (defunct) chamberlain automatic garage
door opener.
Garage door operator security
While manufacturers of garage door operators make excellent claims of
security, this is of no value if you don't take advantage of whatever
features are included in your unit.
Identifying unknown transformer ratings in garage door operator
In a garage door operator, the transformer likely powers the controller
and receiver. If you can look at where its outputs go, you may be able to
infer something about the voltage even if the transformer is a charred mass.
Electromechanical doorbells and chimes
Most of these consist of a low voltage transformer powered directly from
the house wiring providing 10 to 20 VAC at its output, one or more switches
for the front door(s), one or more switches for the back door(s), and an
electromagnetic chimes unit.
Bell Transformer Chimes
H o----+ Unit
)|| X _|_ Front door F
)|| +-----+------- --------------------o
)||( |
115 VAC )||( | _|_ Back door B
(Junction box) )||( +------- --------------------o
)||(
)||( Y C
)|| +----------------------------------o
)||
N o----+
Where the pushbuttons are lighted, a small incandescent bulb is wired across
the switch contacts and mounted inside the button unit. It is unlikely that
this bulb will ever burn out since it is run at greatly reduced voltage.
However, if the button does not light but the bell works, this has happened.
Replace the pushbutton/light combination - locating a replacement bulb may
not worth the effort though Radio Shack is supposed to have something that
will work.
Weak or erratic mechanical chimes
This can be due to several things:
Adding an additional set of chimes
There are at least two ways of doing this (though the first one is more
straightforward and intuitive and therefore generally preferred).
Note: For either of these schemes, beyond some number of chimes units, the
current rating of the pushbutton switches will be exceeded resulting in early
failure. However, this should not happen unless your house is similar in size
to Bill Gates' mansion.
Bell Transformer Chimes Chimes
H o----+ Unit 1 Unit 2
)|| X _|_ Front door F F
)|| +-----+------- --------------------o---------o
)||( |
115 VAC )||( | _|_ Back door B B
(Junction box) )||( +------- --------------------o---------o
)||(
)||( Y C C
)|| +----------------------------------o---------o
)||
N o----+
Bell Transformer Chimes Chimes
H o----+ Unit 1 Unit 2
)|| X _|_ Front door F F
)|| +-----+------- --------------------o---------o
)||( |
115 VAC )||( | _|_ Back door B B
(Junction box) )||( +------- --------------------o---------o
)||(
)||( Y C C
)|| +----------------------------------o +----o
)|| |
N o----+ From output Y of identical o--------+
second bell transformer
(H, N, X, wired in parallel)
How to add an addition button to a door bell
Refer to the diagram in the section: Electromechanical
doorbells and chimes.
Wireless doorbells or chimes
The transmitter and receiver portion of these units are virtually identical
to those of garage door operators. See the relevant sections on those units
for problems with activation.
Doorbell rings on its own
Old garage door operator guts for wireless chime
Don't toss the electronic remains of that old garage door operator. It would
probably be possible to use it as the basis for a wireless doorbell. Instead
of starting the motor, use its output to enable an electronic chime or buzzer.
The RF transmitter and receiver for a wireless chime is virtually identical
to that of a typical garage door operator.
TV antenna rotators
These consist of a base unit with some sort of direction display and knob
and a motor unit to which the TV antenna is mounted. Of course, the
troubleshooting of these installations is complicated by the
remote and somewhat inaccessible location of the motor unit. :-( Before
climbing up on the third story roof, confirm that you haven't lost power
to the motor unit and/or base station and that the connections between
them are secure.
This was connected to a knob switch, which also turned. Scenario is: the unit
is pointed halfway through the circle. turn the knob left, the rotor turns
and the indicator turns with it. when the rotor turns the same number of
"clicks" as you turned the knob, it stops. same for reverse.
5263 Agro Drive
Frederick, MD 21703
Phone 301-874-5885
Web: http://www.rotorservice.com/
Power Tools
Types of motors found in power tools
A variety of motor types are used depending on the type of tool. AC powered
portable tools usually use a universal motor due to it high power/weight
ratio and ease of electronic speed control. Cordless tools usually use a
high performance permanent magnet DC motor. Stationary power tools almost
always use some form of AC induction motor except where variable speed
is required.
Motors in AC line operated portable tools
Line operated portable (corded) power tools usually use a universal type
AC motor providing 3,000 to 30,000 RPM at the motor shaft. For the same
power rating, these will be significantly lighter than an induction motor.
Motors in cordless power tools
These are usually high performance permanent magnet DC motors using advanced
high strength and exotic magnetic materials. They are very compact and light
weight for their power output. As with all DC (brush type) motors, brush
wear is a common problem.
Motors in stationary power tools
Stationary power tools which do not require continuous speed control will
generally use some type of AC induction motor - split phase or capacitor
start/run. The motors generally operate at a fixed speed of around either
1725 or 3450 RPM (U.S., 60 Hz power). Stepped pulleys or continuous mechanical
speed/torque changers are used to obtain (usually) lower work piece speeds.
About horsepower ratings
One horsepower is equal to 746 watts of electrical power (100% efficiency).
Therefore, the most you can get continuously from a normal 115 V 15 A outlet
is about 2 HP. Any claims (for air compressors, for example) of higher
ratings on a normal outlet are totally bogus. Companies such as Sears
(Craftsman) like to specify 'Reserve Power' for their power tools which
as best as I can determine refers to the power available for a short time
and may relate to the mass - and inertia - of the rotating parts but not
the continuous power available. This may be useful to help saw through
a tough knot in a piece of hardwood but may not be terribly meaningful for
a wet/dry vacuum! Therefore, pay most attention to the continuous power
ratings if they can be found anywhere. A good indication is probably the
maximum amps required for the electrical service.
Cords for AC line operated portable power tools
Really old power tools had two wire cord plugs and no safety ground yet were
of all metal (solid and heavy!) construction. I would recommend that as
a matter of policy, these be retrofitted with a 3 wire grounded cordset.
Portable drills
The portable electric drill (now the rage is cordless) is probably one of
the two first tools that any handyman should own (the other being a saber
saw). It is used for many things in addition to drilling little holes -
drilling large holes, sanding, polishing, driving screws, etc. Therefore,
these tools get a lot of use - and abuse.
AC line powered drills
An AC line powered electric drill is just a universal motor with a two stage
(typical) gear reduced powering a chuck to hold the drill bit or attachment.
A continuous range speed control with a reversing switch is now standard
on most AC line powered drills.
