Huntron - Troubleshooting without a Schematic

Our thanks to Huntron for allowing us to reprint the following article.

A technician may be required to repair boards and systems with a minimum of service information. At first glance a circuit card or system may instill panic but upon closer inspection we find that the total board is simply a collage of familiar components arranged in text book configurations. In this article, we will discuss troubleshooting without the aid of a schematic diagram.


THE LIBRARY


A shop library can be an important asset to a successful repair shop. Knowing what an electronic component does can assist you in making troubleshooting decisions. The pin-out information can help locate a fault and supply information needed for pin-to-pin comparison. The right pieces of information can make the difference between success and failure.


  1. There are many data manuals available to the technician for a small fee or free of charge. Manufacturers supply these to encourage people to use their products. These data books normally supply pin out, application, and labeling information. Contact a local distributor or the manufacturer directly to obtain these manuals.
  2. Cross Reference manuals are an important addition to a shop library. These manuals allow you to cross one manufacturer's part number to that of another. This is particularly useful if you have a limited number of data manuals. The better manuals give specifications, pin designations, and numerous replacement possibilities. With the right Cross Reference manual, you can locate replacement parts for American, Asian, and European devices. Some suppliers, for example JDR Microdevices, sell data manuals.
  3. An IC identification manual, for example the IC Master, will tell the purpose, manufacturer, voltage, number of pins, and comparable replacement devices of most (or all) commercial ICs. While supplying a possible clue, these manuals usually will not have information regarding custom ICs.
  4. Electronic circuit manuals can be very useful and are available from a number of technical publishers. They show actual working circuits that can be used as a reference.
  5. Be aware of what you may already have. It is not uncommon to find a part used in many different applications. When looking for a Z80 CPU pin out, you may find that you have another system with a schematic diagram that uses a Z80 CPU also.

REVERSE ENGINEERING


With the preceding library at hand, the first step is to take some note paper and draw a block diagram of the board. Some items to note:...


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