Pop Flamer (Stern/Jaleco) PCB repairs
Problem: Very faint sound, loud static
Tools: schematics, soldering iron, multi-meter
The sound could be heard, just barely when my test rig sound control was
turned all the way up. When I touched IC95, a LM380N, the sound either would muffle, go silent or
give a loud squeal and get very hot. I installed a socket and replaced the LM380N and the problem
remained. The sound pot on the board had no effect on the volume. I probed the sound
output pin on the card-edge connector and it, of course, was pulsing... with static!
Looking hard at the board I could see no broken traces and there were sound pulses.
Replacing the 470 25V electrolytic cap that was between pin 10 of the LM380N and the card edge
connector made the board go silent. Hmm, seems I broke the trace going from pin 10 on
the LM380N to the cap. I jumpered the trace and was back where I started. :-(
Fixing the trace made me start looking at the other elec. caps in the
circuit. Checking the connections from pin 2 on the LM380N to cap between it and VR1,
the sound pot, gave me an 'open' on the multi-meter. If I wiggled the cap it would read
'closed', then 'open' again. Fixing this trace solved the problem.
Solution: Broken traces to electrolytic capacitors going to pins 2 and 10
of IC 95, a LM380N
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