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Typical symptoms are: everything works fine except erratic or no dialing. For some buttons, dial tone would not go away. For others, tones would be accepted but will be erratic and result in incorrect digits. Certain digits may sound weak, wavery, or single frequency (rather than the proper DTMF dual tones). (Note that this is not the same as the situation where the phone does not dial at all - there are no tones of any kind generated. In this case, the wires to the phone may simply be reversed - old ATT touch tone phones will not dial out if they are but will work in all other respects. Modern phones generally don't care about phone line polarity.) While the internal wiring of these old phones is intimidating, the basic tone dialing circuitry is an amazing example of simplicity. About the only things that fail yet still permit some tone generation are the pot core coils that determine tone frequency. Therefore, this is the first thing to check. There are two cores which each consist of two halves glued together. Breaks seem to be a common problem due to both the age and the brittle cement used on some revs of this model phone, and probably, as a result of rough treatment when hanging up the handset, or dropping or throwing of the desk phone. These cores must be aligned before being glued back together. In addition, there is an adjustment plug which may need to be tweaked. I align by ear as follows: Put a known good tone dialing phone and the bad phone on the same phone line. Momentarily depress the hook switches to silence the dial tone. You will now have about 25 seconds before the nice polite operator recording tells you how to make a call. Depending on which core is bad, depress either an entire (same) row or column of buttons on both phones. (Adhesive tape is handy to hold down the buttons unless you have four hands.) By depressing the entire set of buttons, you are disabling the other tone generator so you hear a pure tone. Without turning the fine adjustment plug (assuming it was not disturbed; if it was, set it mid-range or the same as the one in the other core), rotate the loose core top until a zero beat is obtained. As your rotate the core, you will hear the pitch change. As it approaches the correct setting, you will hear the tones beat against each other. When you are set correctly, the pitches will be equal and the beat frequency will go to zero. Mark the position of the core with a pen or pencil and then glue with Epoxy or other general purpose adhesive (around the outside - not on the mating surfaces as this will affect the tone frequencies). After the glue sets, confirm and adjust the plug core if needed. These cores use a strange triangular core tool - I made mine by filing down an aluminum roofing nail (do not use a ferrous material). These classic ATT Touch Tone phones are virtually indestructible. However, broken cores (or actually, just broken joints on the cores) are common but easily repaired once you know what to look for. Setting the tones by referencing a known good phone seems to be a very reliable technique as the zero beat permits an adjustment to better than .1%. Note that if the reference phone is a more modern (and flimsy digital one), then pushing multiple buttons may not work as it does with the old analog models. Setting the frequency using the normal dual tones will work - it is just not as easy.
I know, you haven't seen one of these in years, but I just had to throw this in. Most likely it was dropped - these phones simply do not seem to fail any other way. When dropped, assuming there is no obvious damage, a little plastic stop inside the dial mechanism which is on a pivot flips the wrong way. This normally prevents dialing pulses from being generated when the dial returns to its home position but when flipped, prevents dialing totally. It is real easy to flip it back into place.
The most common symptoms for these cable boxes relate to their not staying on or acting erratically when the buttons are pressed. The causes are usually quite simple: 1. Cold solder joints around the power supply regulator ICs (on chassis heat sink). 2. Dried up main filter capacitors - two large electrolytics in power supply on main board. Be careful disassembling the main board from the chassis as at least one of the regulator ICs clipped to the side of the chassis is insulated from this heatsink and the insulation is easily damaged.
While the original Nintendo game machine is a couple of generations out of date, many are still in use. And, hey, kids usually don't care. The most common problem with these units is a worn or dirty cartridge connector. In this case, the red power/status light will continue to flash even after the RESET button is pressed with a game cartridge in place. Replacements are available for about $9 from the sources listed at the end of this document. First, try another game cartridge - the one that is not working may just have dirty contacts or may be defective. Clean the contacts with a Qtip moistened with water followed by isopropyl alcohol. (The water will remove the sugar from the candy that may have made its way onto the connector.) To get inside, you first remove the 6 screws on the bottom and then about 12 screws which fasten the circuit board and shield to the bottom of the case. (Note: there are two screws which are longer and silver colored - make sure they get back to their original location when you put everything back together.) Once all these screws are removed, the black connector can be slid off the edge finger on the circuit board Inspect these connections - they just may be a bit corroded or dirty. Use contact cleaner and/or a pencil eraser and see if that makes any difference. Use contact cleaner on the dual rows of fingers that connect to the game cartridge as well. A dental pick can be used to gently spread the fingers apart ever so slightly and thus improve the connection when the cartridge is inserted. Even if this only makes a slight improvement - you can press down on the cartridge and the machine will respond to the RESET button - you have confirmed that the connector is indeed the problem. In many cases, just this cleaning will result in reliable operation for a long time to come.
I have them up through TI-57 so I don't know if the following applies to models higher than this (TI-58 and TI-59). If it hasn't been used for a while (like 15 years?) then the NiCds are likely deader than a door nail and will not accept a charge since they are totally shorted. Bad NiCds is very likely all that is wrong with the calculator. If your calculator has a pack that plugs in inside the back with 2 AA NiCds and some circuitry, then it is the same. First crack open the pack by using a butter knife or similar instrument at the catches along the seam. You will see a pair of AA NiCds and a small circuit board. This is a DC-DC convertor which boosts the 2.4 V of the NiCds to about 10 V to operate the logic of the calculator. Inspect the circuit board for corrosion and other obvious damage. Unless the calculator was stored in a damp area, it should be fine. The batteries will probably have crusty white stuff on the positive ends. They are bad. Don't even bother trying to zap them. As a test, you can do either or both of the following: 1. Get a large electrolytic capacitor (e.g., 10,000 uF at 10 V) and put it in in place of the batteries. Observe polarity. Try out the calculator using the TI charger/adapter. Operations will be a bit flakey but should basically work (the capacitor, no matter how large, apparently will not substitute for the NiCds). 2. Unplug the TI battery pack and set it aside. Find a 9 V power supply or a 9V battery. Connect this to the red and black wires coming from the logic board connector which went to the battery pack. NOTE: the wire color coding is backwards on at least some of these. Black is positive for some reason. However, nothing disasterous happens if you connect it backwards as far as I can tell since I was testing it backwards for quite a while until I caught on. And, I thought TI was a real company! If these tests are successful, the calculator is likely fine and you just need a new set of AA NiCds with solder tabs to make it as good as new. Or, if you don't need the authenticity of a genuine TI form-and-function rechargeable battery pack, use a 9V AC adapater, 9V Alkaline, or 9V NiCd battery and charge it externally.
Belts are normally specified by their cross section - square, flat, round, and their inside circumference (IC). The IC is used since it is virtually impossible to accurately measure the diameter of a belt. Assuming you cannot locate an actual part number, determine the type of belt; square, flat, or round. If you do not have the old belt, this is usually obvious from the pulleys. Most small belts (as opposed to V-belts on 1 HP shop motors!) used in consumer electronic equipment are of square cross section though flat types are sometimes found in the main drives of VCRs, cassette/tape decks, and turntables (remember those?). Measure or estimate the thickness. The IC is always specified with the belt fully relaxed. This can be measured by hooking the old belt on one end of a ruler and pulling it just tight enough so that it more or less flattens out. Read off the length, then double it for the IC. Get a new belt that is 5% or so smaller to account for the old one be somewhat stretched out. Of course, if the belt broke, measurement is real easy. Or, if you do not care about the old belt, just cut it and measure the total length. If the old belt decomposed into a slimy glob of jellatinous black goop or is missing, you will need to use a string or fine wire around the appropriate pulleys to determine the IC. Reduce this by 10-25% for the replacement. Very often the match does not need to be exact in either thickness or length - particularly for long thin belts. A common rubber band may in fact work just as well for something like a tape counter! However, there are cases where an exact match is critical - some VCRs and belt driven turntables or tape decks do require an exact replacement for certain drive belts but this is rare. Some parts suppliers make determining replacement belts very easy with the PRB system in which the part number fully codes the shape, size, and thickness. Making custom length rubber belts: --------------------------------- The following will probably work for most drive belts except for those which are critical for accurate speed control in devices like cassette decks and turntables. (From: Melissa & Jim (mgkepner@facstaff.wisc.edu)). 3M and Eastman make cyanoacrylate adhesives (super glue) that are specially made for making custom O-rings from linear stock. This seems to be exactly the same problem you are approaching. These glues work very well and produce a joint as strong as the base material, but without the need for the needle and thread. The joint can be made almost invisible. The only hard part is holding the pieces aligned while the glue cures, but in this case that is only seconds. I have used a machinists steel V-block for this, but one of the O-ring manufacturers sells a plastic tool for exactly this purpose. In the US, I would check at a bearing supply house; they often carry O-ring supplies as well.
It is 3 AM, you have finally removed the last of the 38 screws to access the tape transport in your Suprex Never-Forget model X4123 answering machine and what do you fine? A broken belt, of course! What to do? As a test at least, a common elastic band may work. The recordings will likely have terrible wow and flutter but this will at least confirm that there is nothing else broken. In a pinch, this free solution can be left in place until a proper replacement arrives. This should work for many types of devices - CD players, VCRs, tape decks, etc. - where grooved pulleys are used and the belt is not called on to provide a great deal of power.
The question often arises: If I cannot obtain an exact replacement or
if I have a VCR, tape deck, or other equipment carcass gathering dust, or
I just have some extra parts left over from a previous project, can I
substitute a part that is not a precise match? Sometimes, this is simply
desired to confirm a diagnosis and avoid the risk of ordering an expensive
replacement and/or having to wait until it arrives.
For safety related items, the answer is generally NO - an exact replacement
part is needed to maintain the specifications within acceptable limits with
respect to line isolation, X-ray protection and to minimize fire hazards.
However, these components are not very common in audio equipment or other
consumer devices (other than TVs, monitors, and microwave ovens) except for
possibly in their power supply.
For other components, whether a not quite identical substitute will work
reliably or at all depends on many factors. Some designs are so carefully
optimized for a particular part's specifications that an identical
replacement is the way to return performance to factory new levels.
Here are some guidelines:
1. Fuses - exact same current rating and at least equal voltage rating.
I have often soldered a normal 3AG size fuse onto a smaller blown 20 mm
long fuse as a substitute. Also, they should be the same type - slow
blow only if originally specified. A fuse with a faster response
time may be used but it may blow when no faults actually exist.
2. Resistors, capacitors, inductors, diodes, switches, trimpots, lamps and
LEDs, and other common parts - except for those specifically marked as
safety-critical - substitution as long as the replacement part fits
and specifications are met should be fine. It is best to use the same
type - metal film resistor, for example. But for testing, even this is
not a hard and fast rule and a carbon resistor should work just fine.
3. Potentiometers - user knobs usually control one or more of these. There
are four considerations in locating a suitable replacement: resistance,
and taper, power rating, configuration, and mechanical fit. Configuration
refers to the number of ganged pots, concentric knobs, etc. Matching
this from your junk box may prove to be the toughest challenge! Many
of the controls for audio equipment use what is known as an 'audio taper'.
This means that the resistance change with knob rotation is not linear
but is designed to produce a uniform incremental change in perceived
volume, for example. Replacement with a linear taper pot will squish
all of the effect towards one end of the range but it will still work.
If measuring the resistance of a (good) potentiometer with its wiper
set in the middle results in significantly different readings from center
to each end, it is most likely an audio taper pot (though some other
weird taper or other peculiarity is possible).
4. Rectifiers - many are of these are high efficiency and/or fast recovery
types. Replacements should have equal or better PRV, If, and Tr
specifications. For line rectifiers, 1N400x types can usually be used.
5. Transistors and thyristors (except power supply choppers) - substitutes
will generally work as long as their specifications meet or exceed those
of the original. For testing, it is usually ok to use types that do not
quite meet all of these as long as the breakdown voltage and maximum
current ratings are not exceeded. However, performance may not be quite
as good. For power types, make sure to use a heatsink.
6. Switching power supply transistors - exact replacement is generally
best but switchmode transistors that have specifications that are at
least as good will work in many cases. See the documents: "Notes on
the Troubleshooting and Repair of Television Sets", "Notes on the
Troubleshooting and Repair of Computer and Video Monitors", and "Notes
on the Troubleshooting and Repair of Small Switchmode Power Supplies"
for more info.
7. Audio and erase heads - may be possible if the mountings are reasonably
compatible. However, there could be other unknowns like coil impedance
and drive requirements. The connectors are not likely to be similar
either. There are usually significant differences in head configuration
and mounting arrangement between 2 head, 3 head, and autoreverse cassette
or open reel tape decks.
8. Motors - small PM motors may be substituted if they fit physically.
Make sure you install for the correct direction of rotation (determined
by polarity). Capstan motors - especially the direct drive type - are
probably not interchangeable. However, generic speed regulated
cassette drive motors are available.
9. Sensors - many are sufficiently similar to permit substitution.
10. Power transformers - in some cases, these may be sufficiently similar
that a substitute will work. However, make sure you test for compatible
output voltages to avoid damage to the regulator(s) and rest of the
circuitry. Transformer current ratings as well as the current
requirements of the equipment are often unknown, however.
11. Belts, tires, and pinch rollers - a close match may be good enough at
least to confirm a problem or to use until the replacements arrives.
12. Mechanical parts like screws, flat and split washers, C- and E-clips,
and springs - these can often be salvaged from another unit.
The following are usually custom parts and substitution of something from
your junk box is unlikely to be successful even for testing: SMPS (power
supply) transformers, interstage coils or transformers, microcontrollers,
other custom programmed chips, display modules, and entire power supplies
unless identical.
It is not uncommon for parts to be missing from production equipment due to design changes or field mods. Thus, it may not mean anything. Inspect the solder pads - if they look the same as all the others, it was probably never installed in the first place. Of course, that could have been a manufacturing omission as well. Parts just don' jump ship without leaving evidence behind! Don't be tempted to add a part just because there is an empty spot. In some cases, like the RCA TV that would tend to blow HOTs if the power failed, that would be a really bad idea and complicate your troubleshooting. Whole blocks of circuitry are often left unpopulated on lower priced models. You didn't pay for those features. Sometimes, this can work to your advantage enabling you to upgrade to a fancier model for the cost of the parts.
Tandy (Radio Shack) has a nice web resource and fax-back service. This is mostly for their equipment but some of it applies to other brands and there are diagrams which may be useful for other manufacturers' VCRs, TVs, CD players, camcorders, remote controls, and other devices. http://support.tandy.com/ (Tandy homepage) http://support.tandy.com/audio.html (Audio products) http://support.tandy.com/video.html (Video products) Since Tandy does not manufacture its own equipment - they are other brands with Realistic, Optimus, or other Radio Shack logos - your model may actually be covered. It may just take a little searching to find it.
Here are some suggested titles that might be found in your local public
library or a technical bookstore.
1. Troubleshooting and Repairing Electronic Circuits
Robert L. Goodman
Second Edition
TAB Books, Inc., 1990
Blue Ridge Summit, PA 17294-0214
2. Small Electric Motors
Rex Miller and Mark Richard Miller
Second Edition, 1992
MacMillan Publishing Company
866 Third Avenue
New York, NY 10022
3. Repairing Quartz Watches
Henry B. Fried
American Watchmakers Institute Press, 1988
Cincinati, OH
ISBN 0-918845-06-8
4. Readers Digest Fix It Yourself Manual
The Readers Digest Association, 1996
Pleasantville, New York/Montreal
ISBN 0-89577-871-8
5. The Complete Guide to Digital Audio Tape Recorders
including Troubleshooting TIps
Erik S. Schetina
P.T.R. Prentice Hall,
Englewood Cliffs, NJ 07632
ISBN 0-13-213448-9
6. DAT - The Complete Guide to Digital Audio Tape
Delton T. Horn
TAB Books, Inc., 1991
Blue Ridge Summit, PA 17294-0214
ISBN 0-8306-7670-8 (hardcover), ISBN 0-8306-3670-6 (paperback)
7. Troubleshooting and Repairing FAX Machines
Gordon McComb
Tab Books, a division of McGraw-Hill, Inc., 1992
Blue Ridge Summit, PA 17214
ISBN 0-8306-7778-X (hardcover), 0-8306-3778-8 (paperback)
8. Complete Guide to Home Entertainment Equipment - Troubleshooting and Repair
John D. Lenk
Prentice Hall, Inc., a division of Simon and Schuster, 1989
ISBN 0-13-161001-5
9. Understanding Telephone Electronics
Fike and Friend
10. Installing Telephones
Radio Shack
Catalog number: 62-1060
11. All Thumbs Guide to Telephones and Answering Machines
Gene B. Williams
TAB Books, Inc., 1993
Blue Ridge Summit, PA 17294-0214
ISBN 0-8306-4435-0 (paperback)
This one is very basic but does cover the most common problems and has
illustrated instructions for general telephone wiring, adding extensions,
answering machine cleaning, rubber parts, simple electronic problems, etc.
And, for that older audio equipment (including record changers):
12. Repairing Home Audio Systems
E. Eugene Eckland
McGraw-Hill Book Company, 1962
Library of congress catalog number: 61-18021
For general electronic components like resistors and capacitors, most
electronics distributors will have a sufficient variety at reasonable
cost. Even Radio Shack can be considered in a pinch.
However, for consumer electronics equipment repairs, places like Digikey,
Allied, and Newark do not have the a variety of Japanese semiconductors
like ICs and transistors or any components like tape heads or belts.
The following are good sources for consumer electronics replacement parts,
especially for VCRs, TVs, and other audio and video equipment:
* MCM Electronics (VCR parts, Japanese semiconductors,
U.S. Voice: 1-800-543-4330. tools, test equipment, audio, consumer
U.S. Fax: 1-513-434-6959. electronics including microwave oven parts
and electric range elements, etc.)
Web: http://www.mcmelectronics.com/
* Dalbani (Excellent Japanese semiconductor source,
U.S. Voice: 1-800-325-2264. VCR parts, other consumer electronics,
U.S. Fax: 1-305-594-6588. Xenon flash tubes, car stereo, CATV).
Int. Voice: 1-305-716-0947.
Int. Fax: 1-305-716-9719.
Web: http://www.dalbani.com/
* Premium Parts (Very complete VCR parts, some tools,
U.S. Voice: 1-800-558-9572. adapter, cables, other replacement parts.)
U.S. Fax: 1-800-887-2727.
* Computer Component Source (Mostly computer monitor replacement parts,
U.S. Voice: 1-800-356-1227. also, some electronic components including
U.S. Fax: 1-800-926-2062. semiconductors.)
Int. Voice: 1-516-496-8780.
Int. Fax: 1-516-496-8784.
Also see the documents: "Troubleshooting of Consumer Electronic Equipment" and
"Electronics Mail Order List" for additional parts sources.
There is no Next. THE END
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