Henry Kolesnik wrote:

Sometime ago I think I recall someone posted or wrote an article on a neat
way to isolate a shorted component on a pcb using common test eqpt but I
can't recall the methodology. I'm trying to find a shorted component on a
Wavetek 188-S-1257 signal generator. The B+ line reads about 0.4 ohms and
I'm not having much luck disconnecting componets. I don't have a schematic
and my eyes ain't what they used to be for tracing and I want to minimize
the unsoldering. Does anyone recall the article or have a good way?
tnx
hank wd5jfr

Use an adjustable DC power supply to feed the shorted power rail. Use
16 gauge, or larger wire to minimize the voltage drop. Make sure to
connect the meter negative to ground at the same point you connect the
adjustable power supply to the bad board. Set the adjustable DC power
supply to about a half amp, and use a DC voltmeter to read the voltage
drops across the traces. You will find a point where they level off.
Back up one part to the last linear voltage drop and you have found your
bad part. I prefer to use a 4½ digit voltmeter, or better to read minor
variations. Also, check the voltage on the ground buss if the board
isn't bolted to a chassis to find which part of the board has the
problem. I have fixed hundreds of shorted boards this way.

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Michael A. Terrell
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