Bump this for the both of us. I'm interested in this as well. Recently bought a Circus and was told sound could be flakey at times.

Do you have the manual and schematics? Input voltages and test points should be marked.

I don't even start any sound board diagnosis until I replace/repair all the usual suspects that tend to fail or cause known headaches. I replace all old electrolytic caps on the board since they need it anyway. I replace all punch pin type connectors in the A6J1 connector with crimp type since the failure rate seems high to me. I also test out the speaker(s)/volume control since they can also go bad. Sometimes, by the time I do those things, the sound board starts working again. Without doing these things, you can't really get a true diagnosis if it's a board problem, especially if there is more than one issue.

Steve
System 80, not just a job, it's an adventure

Bump

FYI, from what I recall, there is no background sound on this game, just sounds for switch hits.

Giving a bump as I'm interested in this problem as well. Chris,Vid one of you chime in and give some of your wisdom up! Blownfuse, I know you have a Circus and I will go over mine for the usual stuff Thx!

Sorry necroing this thread. I can start a new one if preferred. Anyway we have a Circus with an odd sound issue. We can hear the sounds but very faintly. Volume control does work as when the sound is turned completely down no sounds are audible. With volume turned up you can just barely hear the sounds. So the machine is producing sound but it’s barely audible. Any ideas?

Apologies for bringing back up an old post, and I'm sure this is too late to help Chisel with his issue, but I had the exact same problem as he is describing and found that replacing the cap at C8 on the board brought back the volume. I had originally thought it was the LM380N Amp, but it turned out to be C8. It leaked on the bottom where you cannot see and corroded the connections bad enough to make the sound flake out.