Thursday, January 22, 2009

Don Matsuda's "Electronic Troubleshooting" - revisited

A SMD (surface-mount device) FTDI chip, on the...Image via Wikipedia

The other week, I had an opportunity once again to browse through the book by Don Matsuda “Electronic Troubleshooting”. This was a book that I was fortunate to have bought - and read - many years ago when I was just starting out on doing electronic repairs professionally.

In the preface to his book Don Matsuda notes that Troubleshooting has its own rules. He notes further that the rules are derived from everyday practice and must be taught from the point of view of practice.

Matsuda starts out the book by mapping out a “game plan” for troubleshooting. The game plan is divided into 5 phases.

Phase 1: The Outside

Starts the troubleshooting approach from outside of the equipment under complain. Identify the symptoms. Make the preliminary inspection of the equipment by operating it and evaluating its performance. Decide whether the trouble is in the equipment or the environment. Interview the user to get a background of the problem from his standpoint. Let him know of any problem you see or foresee be before you start out work on the equipment.

Phase 2: The Gateways Into The Circuits

This is when the troubleshooter goes deeper into the root of the problem and begins an approach into the “gateways into the circuits” . Two of these gateways are the input and output devices. Troubles in electronic equipments can be caused by a malfunctioning input device and symptoms will show up at the output. Or the output device itself is defective. Symptoms can be clues that our four senses can pick up or can be measured by our test instruments. An analysis of the symptom is a step towards finding out the right cure.

Phase 3: Working Your Way In

This involves getting down to the nitty-gritty of instrumentation work. DC voltages have to be measured and bad voltages pinpointed. Trace a signal and identify the stage in its path where it deteriorated.

Phase 4: Nailing Down The Bad Part

This involves locating the defect to the bad part. After pinpointing the defective section a test of its components should reveal the defective part/s.

Phase 5: Cooking

This is what is sometimes called 'burn-in test'. After the bad parts have been replaced the equipment is operated for about 20 minutes or longer depending on the type of fault.

In the book, Matsuda also presents some general strategies in troubleshooting. These are:

  1. Trial and Error; Divide and Conquer. If something does not work, try another solution. Cut up problems into little ones and deal with them one at a time. Follow up on one of your hunches, if it turns out to be wrong, at least you have eliminated it as a possibility. Troubleshooting is not a cut-and-dried process. But keeping the game plan in mind will keep us from getting sidetracked.

  2. Questioning and Thinking Things Over . Question all leads you come across. Poll all possibilities.

  3. Playing the Percentages. Troubleshooters pay special attention to parts or sections in an equipment that have a high failure rate. Parts and sections under great heat, electrical and mechanical stress have the highest failure rate.

  4. The Divide-in-Half Procedure; Divide and Conquer. Mentally divide a circuit in half and test each half. When you identify the bad half divide it again and test. This dividing and testing is repeated until the defective part is located. This is faster than testing the parts one by one.
    In Steve Litt's 10 Step Universal Troubleshooting Process, the Divide and Conquer procedure is also discussed in detail.

  5. Doing the Easy Things First. “When the odds seem pretty equal – and sometimes when they're not – it is best to do the easiest thing first.... At least you will quickly eliminate a possibility and feel better about taking on the more difficult and time-consuming alternative.”

The book then continues by giving valuable discussions and tips on doing voltage tests: what bad voltages tell, which part must be causing the problem. Also very informative are the sections and chapters on checking transistor circuits, amplifiers, power supplies, high voltage circuits, oscillators, high frequency circuits, TV, linear and digital ICs.

Also, the section discussing the “Nature and Frequency of Parts Failures” gives valuable tips on what parts fail most often. The book reveals that the part that fails most often are transistors. Capacitors come in second place as the part that has the highest failure rate. Resistors come third. And then coils and transformers.

In the last chapter of the book which deals with troubleshooting intermittent tough dog troubles, Matsuda advices to get hold of a piece of discarded electronic equipment that a pro technician has wisely turned down and get ready for some real troubleshooting. “However, it is a challenge and a real learning experience, even if you fail.”

In troubleshooting as in life, failure teaches as much as success.

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