If I asked you to fix a 1992 WPC Williams Driver board based solely
on a bad General Illumination circuit... what would you say to me?



While I have no experience with those, I would look over the board, follow
the outputs back to identify the GI portion of the board, then look for the
usual suspects such as cracked solder joints or obviously burned parts, then
test any semiconductors with a multimeter. If it isn't raw AC from the
transformer, then I would expect it to be a fairly standard linear power
supply.

The same is true with an amp, or virtually any other piece of analog
equipment. Look it over and get a rough visual identification of the
sections, make an educated guess as to which areas are most likely to
contain the problem, look for obvious visual fault indications, and then
start testing the individual components for faults. In this case, test the
output devices, if those are not shorted, test the driver components and
bias resistors. Usually the problem will be in one of those areas, but if it
isn't, work your way back. If you don't find anything shorted, apply power
and verify that the supply rails are present and that the voltage is
something reasonable. The schematic for any power amplifier of similar
construction (discrete vs monolithic output stage) should be similar enough
to give you an idea of the circuit.