Repair Logs

Pop Flamer (Stern/Jaleco) PCB repairs

03/13/2000

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