Some rules of troubleshooting
Because troubleshooting is a logical process, it makes sense to consistently follow a set of guidelines to insure both safety and efficiency of the process. Here's the set of guidelines I follow:

1. Safety first - know the hazards associated with the equipment you are troubleshooting. Take all safety precautions. Expect the unexpected. Take your time.
2. Always think "what if?" This applies both to the analytic procedures as well as to precautions with respect to probing the equipment. When probing, insulate all but the last 1/8" of the probe tip to prevent costly shorts. (If I had a nickel for every time I have caused myself problems not following this advice. . .)
3. Learn from your mistakes. We all make mistakes. Some of them can be quite costly. A simple problem can turn into an expensive one due to a slip of the probe or being over eager to try something before thinking it through. While stating that your experience in these endeavors is measured by the number of scars you have may be stretching the point, expect to make mistakes - we all can point to that disaster due to inexperience or carelessness. Just make it a point not to make the same mistake again.
4. Don't start right in with the electronic test equipment, start with some analytical thinking. Many problems associated with consumer electronics equipment do not require a schematic diagram (though one may be useful). Most problems with VCRs, CD players, tape decks, and answering machines, are mechanical and can be dealt with using nothing more than a good set of precision hand tools; some alcohol, degreaser, contact cleaner, 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.
5. 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).
6. Many problems have simple solutions. Don't immediately assume that your problem is some combination of esoteric complex convoluted failures. For a TV, it may just be a bad connection or failed diode. For a VCR, it may just be a bad belt or idler tire - or an experiment in rock placement by the owner's 3-year old. For a CD player, the cause of a malfunction may simply be a dirty lens or need for lubrication. Try to remember that the problems with the most catastrophic impact on operation, a dead TV or a VCR that eats tapes, usually have the simplest solutions. The kind of problems we would like to avoid at all costs are the ones that are intermittent or difficult to reproduce: subtle color noise, the occasional interference, or the dreaded horizontal output transistor blowing out every 3 months syndrome.
7. Whenever possible, try to substitute a working unit. With modular systems like component stereos and computers, narrowing down a problem to a single unit should be the first priority. This is usually safe to do in such cases and will quickly identify which unit needs work. This same principle applies at the electronic or mechanical parts level. Note that there is the possibility of damaging the known good part by putting it into a non-working device or vice versa. This risk is most likely with the power circuitry in amplifiers, TVs and monitors, power supplies, etc. With appropriate precautions (like placing a light bulb in series with the power line to limit the current), the risk can be minimized.
8. Don't blindly trust your instruments. If you get readings that don't make sense, you may be using your equipment in a way that is confusing it. As examples, DMMs are not good at checking semiconductors in-circuit, or the power transistor you are testing may have a built in damper diode and/or base resistor. Your scope may be picking up interference which is swamping the low level signal you are searching for (TVs and monitors, or low level circuits in VCRs and CD players). Your frequency counter may be double triggering due to noise or imperfect signal shape.
9. Realize that coincidences do happen but are relatively rare. Usually, there is a common cause. For example, if a TV has no vertical deflection and no picture, it is much more likely that a common power supply output has failed than for parts in both the deflection and video subsystems to be bad. In other words, first look for a common root cause rather than trying to locate bad parts in separate circuits. Exceptions include damage caused by lightning, power surges, dropping of the product, water, or incompetence or carelessness of the previous repair person. Another possible cause of multiple failures is the case in which multiple electrolytic capacitors in older equipment may be deteriorating, resulting in failures of unrelated circuits. Determine if all the problems you are troubleshooting have just appeared. It is very common to be given a device to repair which has now died totally, but prior to this exhibited some behavior that you consider marginal but that was not noticed by the owner.
10. Confirm the problem before diving into the repair. It is amazing how many complaints turn out to be impossible to reproduce or are simple cockpit error. It also makes sense to identify exactly what is and is not working so that you will know whether some fault that just appeared was actually an existing problem or one that was caused by your poking. Try to get as much information as possible about the problem from the owner. If you are the owner, try to reconstruct the exact sequence of events that led to the failure. For example, did the TV just not work when turned on or were there some preliminary symptoms like a jittery or squished picture prior to total failure? Did the problem come and go before finally staying bad for good?
11. Get used to the idea of working without service literature in some cases. While service information for TVs is nearly always available in the form of Sams Photofacts, this is hardly ever true of other types of equipment. Sams VCRfacts, for example, exist for less than 10 percent of VCR models and only the older ones include anything beyond (obvious) mechanical information. While a service manual may be available from the manufacturer of your equipment or another Sams-like source, it may not include the information you really need. Furthermore, there may be no way to justify the cost for a one time repair. With a basic understanding of how the equipment works, many problems can be dealt with without a schematic. Not every one, but quite a few.
12. Whenever working on precision equipment, make copious notes and diagrams. 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.
13. Pill bottles, film canisters, and plastic ice cube trays come in handy for sorting and storing screws and other small parts after disassembly. This is particularly true if you have repairs on multiple pieces of equipment under way simultaneously.
14. Select a work area which is wide open, well lighted, and where dropped parts can be located - not on a deep pile shag rug. 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 for storage.
15. Understand the risk of ESD - Electrostatic Discharge. Some components (like ICs) in solid state electronic devices are vulnerable to ESD. There is no need to go overboard but taking reasonable precautions such as getting into the habit of touching a safe ground point first. Warning: Even with an isolation transformer, a live chassis should not be considered a safe ground point. This applies mostly to TVs, computer and video monitors, some ac operated strobe lights, and other line connected devices. You shouldn't be touching components with the device powered and plugged in (at least, not until you really know what you are doing). Once the unit is unplugged, sheet metal shields or other ground points should be safe and effective.

Some quick tips or rules of thumb
After a technician gains a certain amount of experience, he learns that there are certain symptoms that generally are caused by specific conditions. Here are some things I have learned along the way.

• Problems that are erratic or intermittent, that come and go suddenly, are almost always due to bad connections: cold solder joints or internal or external connectors that need to be cleaned and reseated. It is amazing what a large percentage of common problems fall into the category. When dealing with intermittents, pay particular attention to areas of the circuit board where there are large and/or high power components, connectors, or evidence of discoloration or actual charring due to excessive heat. Your eyeballs, a bright light, and magnifier will be the most useful test equipment for this purpose.
• Problems that change gradually, usually they decrease or disappear as the equipment warms up, are often due to dried up electrolytic capacitors. While capacitors will occasionally leak, making diagnosis easy, in most cases there are no obvious signs of failure. (Note: Don't be misled into thinking that the adhesive often used to anchor large capacitors and other components to the circuit board is leakage.) The most useful testing device for electrolytic capacitors is an ESR meter.
• Problems that result in a totally dead unit or that affect multiple functions are generally power supply related. These are usually easy to fix. Common failure items are the large hybrid power regulator ICs used in many VCRs and TVs, diodes and transistors, and, remarkably, high value resistors that open up.
• Catastrophic failures often result in burnt, scorched, cracked, exploded, or melted components, or similar catastrophic consequences. However, some components run hot by design and slight discoloration on the circuit board in their vicinity, while not desirable, may be normal. Use your senses of sight and smell for the preliminary search for such evidence.
• Listen for signs of arcing or corona: snapping or sizzling sounds. A component on the brink of failing due to overheating may provide similar audible clues. Some discharge sounds are normal for a TV or monitor when powered on or off and occasional sounds of thermal expansion are nothing to worry about. The flyback, yoke, or other (usually) magnetic component may also emit a buzz or whine constantly or intermittently without any other symptoms or implication of impending doom. However, repeated loud snaps or sizzling sounds accompanied by the smell of ozone should be dealt with immediately since they can lead to more serious and expensive consequences.
• Most VCR problems are mechanical in nature. Worn or deteriorated rubber parts, gummed up lubrication, or abuse (bad tapes or toy or peanut butter and jelly sandwich storage). For any problem but a totally dead VCR, a check should be made for dirty or worn mechanical parts before even thinking about electronic problems or trying to locate a schematic; especially if the unit hasn't been cleaned in a few years.
• Many CD player problems are mechanical: dirty lens, worn or oily drawer belts, dirt/gummed up grease on sled tracks/gears, bad/partially shorted spindle, or sled motor. Power problems with portables seem to be common as well. No matter what the symptoms, always make it a habit to clean the lens first; many peculiar failure modes are simply due to a dirty lens. Actual laser failure is relatively uncommon. CD players are also remarkably robust. Optical alignment should never be needed under normal conditions of operation.
• TV and monitor problems are very often power supply or deflection related. These problems tend to have obvious causes: blown posistor, rectifier diodes, filter capacitor, HOT, or chopper. Flyback with shorted windings or shorts between windings or in the voltage multiplier (if used) or screen/focus divider network are also common. Where the HOT or chopper is involved, operation should be observed after the repair, as components in the vicinity may cause the new parts to fail. HOTs should generally not run hot. If they do, check for weak drive, excess B+, etc.
• Microwave oven problems are almost always power related. Faulty components in the microwave generator (magnetron), HV diode, HV capacitor, and HV transformer, are relatively easy to identify. Sometimes, components on the primary side can cause baffling symptoms like the misaligned interlock switches that blow fuses or the weak triac that causes the oven to blow the main fuse only when the cycle ends. Control problems may be due to a spill in the touchpad, dried up electrolytic capacitors in the low voltage power supply, or failure confused state due to a power surge.
• Ink-jet printers are extremely reliable electrically. Look for simple problems such as caked ink in the "service station" area, misaligned print-head contacts, or a nearly empty cartridge when erratic printing problems develop.
• Laser printers tend to develop problems in the fuser, scanner, or power control modules. These are often simple like a burned out lamp, bad motor, or bad connections.
• Turntables or record changer problems are very likely to be due to gummed up grease.
• Problems with audio tape decks like VCRs are mostly mechanical. Similar solutions apply. Where one channel is out, suspect a broken wire at the tape head before blaming a bad chip.
• Telephone line connected equipment like modems and phones are susceptible to phone-line surges. Where a device seems to respond to user commands but does not dial or pickup, suspect a blown part near the phone line connector.
• Use a moistened finger to probe low voltage circuits. This has come to the rescue many times. Touching various parts of a circuit from the solder side of the board in an attempt to evoke some sort of response can work wonders. Once a suspect area has been identified, use a metal probe or nail to narrow it down to a specific pin. The reason this works is that the reduced resistance of your moist skin and your body capacitance will change the signal shape and/or introduce some slight signal of its own.
• Logic circuits - marginal timing or signal levels will change dramatically in behavior with a slight "body" load. It has been possible to locate a race condition or glitchy signal on a 305 pin PGA chip using this approach in less time than it would have taken to roll the logic analyzer over to the system under test. Signals which have proper levels and timing are generally remarkably immune to this sort of torture.
• Analog circuits - behavior can again be altered. In the case of audio amps, probing with a finger is just as effective as the use of a signal injector, which is what you are doing, - and the equipment is always handy. By evoking hum, buzz, clicks, and pops, locating the live or dead parts of a circuit is rapid and effective.
• Unknown circuits - where no schematics are available, it may be possible to get the device to do something or locate an area that is sensitive to probing. The function of a section of circuitry can often be identified by observing the effects of touching the components in that area. For example, I was able to quickly identify the trigger transistor in a wireless door bell by using my finger to locate the point that caused the chimes to sound. This quickly confirmed that the problem was in the RF front end or decoder and not the audio circuitry.
• Bad bypass capacitors - touching the power/signal side of a good bypass cap should result in little or no effect. However, a cap with high ESR and/or reduced capacitance will not be doing its job bypassing the pickup from your finger to ground: when you touch it, there will be a dramatic effect in audio or video systems. If you try this technique, don't get carried away. Too much moisture may have unforeseen consequences. Depending on the condition of your skin, a tingle may be felt even on low voltage circuits under the right conditions. However, this is pretty safe for most battery-operated devices, TTL/CMOS logic, audio equipment (not high power amps), CD players, VCRs (not switching power supply), etc. Warning: Make sure you do this only with low voltage circuitry. You can easily fry yourself if you attempt to troubleshoot your TV, computer monitor, photoflash, or microwave oven in this manner!

On-line tech-tips databases
A number of organizations have compiled databases covering thousands of common problems with VCRs, TVs, computer monitors, and other electronic equipment. Most charge for their information but a few, accessible via the Internet, are either free or have a minimal monthly or per-case fee. In other cases, a limited but still useful subset of the for-fee database is freely available. A tech-tips database is a collection of problems and solutions accumulated by the organization providing the information or other sources based on actual repair experiences and case histories. Since the identical failures often occur at some point in a large percentage of a given model or product line, checking out a tech-tips database may quickly identify your problem and solution. In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts. My only reservation with respect to tech-tips databases in general, this has nothing to do with any one in particular, is that symptoms can sometimes be deceiving and a solution that works in one instance may not apply to your specific problem. Therefore, an understanding of the hows and whys of the equipment, along with some good old-fashioned testing, is highly desirable to minimize the risk of replacing parts that turn out not to be bad. The other disadvantage - at least from one point of view - is that you do not learn much by just following a procedure developed by others. There is no explanation of how the original diagnosis was determined or what may have caused the failure in the first place. Nor is there likely to be any list of other components that may have been affected by overstress and may fail in the future. Replacing Q701 and C725 may get your equipment going again, but this will not help you to repair a different model in the future. One alternative to tech-tips databases is to search at Deja.com (http://www.deja.com/home_ps.shtml - formerly Deja-News) for postings with keywords matching your model and problem and the newsgroup sci.electronics.repair. Having said that, here are some tech-tips sites for computer monitors, TVs, and VCRs. You may find that some of these websites may have moved or closed down, but because websites sometimes come and go erratically, we include them all for your information.

• Anatekcorp Tech Forum (free)
  http://www.anatekcorp.com/techforum.htm
• Repair World (monthly fee)
  http://www.repairworld.com/
• Electronic Repair Tips Home Page (free)
  http://elmswood.guernsey.net/

Here is one for TVs, VCRs, camcorders, and audio. There is also some specific information on RCA EEPROM contents and Sony service tips. It includes a technical forum (discussion group) and is currently free but is not as comprehensive as some of the others:

• Technician's Desk Reference
  http://www.1stchoiceav.com/toc.htm

Here is a site from which you should be able to download a fully operational version of a database with over 115,000 tips for TVs, VCRs, camcorders monitors, microwave ovens, audio equipment, and more. It will work for 14 days and can be purchased and registered during this time. There are versions for both Windows (WinSTIPS) and DOS (SVCTIPS).

• WinSTIPS and SVCTIPS Page
  http://www.servicesoftware.com/winstips.asp

They also offer ServiceTalk (http://www.servicesoftware.com/servicetalk.asp), an on-line discussion group for electronics repair professionals. This members-only forum has access to a subset of WinSTIPS (about 17,000 tips).

Here is a comprehensive tech-tips database just for VCRs that is currently free:

• Fixer - VCR Repair Instruction (Quite extensive)
  http://www.fixer.com/dbase

This site has quite a bit of info for TVs:

• TV Technical Assistance
  http://wa6ati.com

The following site is just for monitors. It may require a relatively small charge. However, this may include a personal reply from a technician experienced with your monitor so it could be well worth it:

• KMR Technical Services Tech Support
  http://www.kmrtech.com/

The following is specifically for microwave ovens. In addition to a large database of specific repairs, there is a great deal of useful information and links to other sites:

• MicroTech Home Page (Everything you always wanted to know about microwave ovens)
  http://www.gallawa.com/microtech/

These types of sites seem to come and go, so it is worth checking them out from time-to-time even if you don't have a pressing need. If possible, download and archive any useful information for use on a rainy day in the future. Some also include many useful links in addition to the tech-tips info so they are worth checking out even if you don't have a specific symptom to deal with.

Getting inside consumer electronic equipment
Manufacturers seem to take great pride in being mysterious as to how to open their equipment. This is not always the case, but is too common to just be a coincidence. Opening the equipment non-destructively may be the most difficult and challenging part of many repairs! A variety of techniques are used to secure the covers on consumer electronic equipment:

1. Screws. Yes, many still use this somewhat antiquated technique. Sometimes, there are even embossed arrows on the case indicating which screws need to be removed to get at the guts. In addition to obvious screw holes, there may be some that are only accessible when a battery or cassette compartment is opened or a trim panel is popped off. Screws will often be of the Philips variety. (Strictly speaking, many of these are not actual Philips head screws but a slight variation. Nonetheless, a Philips screwdriver of suitable size will work on them.) A precision jeweler's screwdriver set, including miniature Philips head drivers, is a must for repair of miniature portable devices. Sometimes, you will find Torx or a variety of security-type fasteners. Suitable driver bits are available. Sometimes, you can improvise using regular tools. In the case of security Torx, the center post can usually be broken off with a pair of needlenose pliers allowing a normal Torx driver to be used. In a pinch, a suitable size hex wrench can substitute for a Torx driver. Many distributors carry a variety of security bits.
2. Hidden screws. These will require prying up a plug or peeling off a decorative decal. Unfastening these fasteners will make it obvious that you were tinkering; it is virtually impossible to put a decal back in an undetectable way. Sometimes, the rubber feet can be pried out revealing screw holes. If there's a stick-on label, rub your finger over it. This may permit you to locate a hidden screw hole. Just puncture the label to access the screw as this may be less messy then attempting to peel it off.
3. Snaps. Look around the seam between the two halves. You may (if you are lucky) see points at which gently (or forcibly) pressing with a screwdriver will unlock the covers. Sometimes, just going around the seam with a butter knife will pop the cover at one location which will then reveal the locations of the other snaps.
4. Glue. Or more likely, the plastic is fused together. This is particularly common with ac adapters (wall warts). In this case, I usually carefully go around the seam with a hacksaw blade taking extreme care not to go through and damage internal components. Reassemble with plastic electrical tape.
5. It isn't designed for repair. Don't laugh. I feel we will see more and more of this in our disposable society. Some devices are totally potted in Epoxy and are throwaways. With others, the only way to open them non-destructively is from the inside. Don't force anything unless you are sure there is no alternative - most of the time, once you determine the method of fastening, covers will come apart easily. If they get hung up, there may be an undetected screw or snap still in place. 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. Been there, done that. And on the still lighter side, from an IBM maintenance manual, circa 1925 (displayed in the Chicago Museum of Science & Industry): "All parts should go together without forcing. You must remember that all the parts you are reassembling were disassembled by you. Therefore, if you can't get them together again, there must be a reason. By all means, do not use a hammer." 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. 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. For those hard-to-open LCD panels: (From: Onat Ahmet (onat@turbine.kuee.kyoto-u.ac.jp). The LCD display housings are usually secured by plastic catches built into the case. They still may have a couple of screws that are positioned in the most innovative places. Obvious places are sides of the display, and under stickers (rub your finger over a sticker and see if you can feel the hole for a screw). Also, try to look around the hinge connecting the LCD to the main housing. Look with the LCD closed, and also open; rotating open the housing might hide some screws from view. Expect it to be awkward. By the way, do not forget small hatches that do not look like one. After that, it is patience, and knowing the right place to twist the case to pop it open. Try not to use screwdrivers; they leave unsightly marks along the seam. Also, if it is your own unit, and you break a few of the catches along the way, don't worry; you can put the housing back together with a few spots of adhesive.

Hand tools
Invest in good tools. This list of basic hand tools is a good place to start.

• Screwdrivers of all types and sizes including straight, Philips, Torx. Security bits for some video games, PS2s, etc. Notched straight blade for VCR mechanical tracking adjustment - make or buy.
• Jewelers screwdrivers - both straight and Philips. These are generally inexpensive but quality is also quite variable.
• Small socket driver set
• Hex key wrenches or hex drivers. Miniature metric sizes for VCRs
• Pliers - long nose, round nose, curved. Both smooth and serrated types are useful
• Adjustable wrench (small)
• Cutters - diagonal and flush. Linesman's pliers.
• Wire strippers, fixed and adjustable. Crimp tool.
• Alignment tools (at least a standard RCA type for coils).
• Files - small set of assorted types including flat, round, square, and triangular.
• Dental picks - maybe a reason to go to the dentist? These are useful for poking and prodding in restricted areas (but you knew that).
• Locking clamps - hemostats - for securing small parts while soldering, etc.
• Magnetic pickup tool - you can never tell when you will drop something deep inside a VCR. If you keep a strong magnet stuck to your workbench, you can use it to magnetize most steel tools such as screwdrivers. Just keep anything magnetized away from the tape path and magnetic heads.
• Hand drill, electric drill, drill press - one or all. A small benchtop drill press (e.g., 8") is invaluable for many tasks. A good set of high speed bits (not the 1000 bits for $9.95 variety). Also, miniature bits for PCB and small plastic repairs.
• Soldering and desoldering equipment.

Emergency screw removal
While a good quality selection of straight, Philips, Torx, and hex-head drivers should handle most screws found in consumer electronic equipment, a couple of other types do turn up and can really be a pain to remove intact. It may be possible to remove such screws even if nothing in your driver assortment quite fits (short of buying the proper tool, that is. What a concept!). There is also the situation (very common) where someone (we won't say who) has pre-mangled the screw head! Here are a few approaches to try when you are stuck at 2:00 a.m. on a Sunday morning with an uncooperative screw:

1. Select a driver type (usually Philips) and size that provides the best grip. Then apply as much pressure as is safely possible without destroying anything and attempt to turn the screw. What you want to avoid is slippage. Once the blade slips, the head will be quickly destroyed and then you are left with options (2) or (3), below. For a jeweler's type screwdriver, clamping something larger to its shaft can provide valuable additional leverage.
2. Use a hand grinder (e.g., Dremel tool) or thin file to create a slot in the screw head which one of your straight-blade screwdrivers will fit. Obviously, take care to avoid damage to adjacent parts and dam off the area to prevent grinding chips from getting over everything.
3. Grab the center and edge of the screw with a pair of sharp diagonal cutters and turn it. This, of course, also damages the screw head and if you are too forceful, will break your cutters as well.
4. Drill out the screw using a bit just large enough to sever the head from the shank of the screw. Then, use a pair of needlenose pliers to unscrew what remains. For large screws, drill only part way and then use a screw extractor like Easy-Out. Note: Some of these screws have had some material like Lock-Tight (which looks like colored nail polish) applied to the top to prevent the screw from loosening on its own. This also prevents the blade of a screwdriver from properly seating, so removal of the Lock-Tight is essential before attempting removal.

• There are also JIS (Japanese Industry Standard) heads. These look just like Philips, but the screwdriver is a little flatter on the end. Not surprisingly, these do turn up in Japanese products.