Recently acquired a Comet that I am nursing back to life. I have it playing pretty decent at the moment but now that I am able to play longer on it a new problem has surfaced. If I leave the machine on or play a few games on it, the sounds cuts out. I can sometimes faintly hear some sounds if I strain my ears, but just a low level hum is left. If I turn the machine off for a while and come back later, no sounds issues.

So I assume this is not a wiring issue but needs some pointers on where to look next. I felt the sound chips and one or two feel much hotter then the rest but not sure what is normal.

Appreciate the help!

Evening bump, any pointers are appreciated.

I am adding some pics of my main board and my sound board to help facilitate. I feel ready to tackle this with more info. I just need help to identifying the where the heat sink is. I can try re-greasing it tomorrow as this is something I have had to do on my PCs many times. And yes, before any one asks, once this pin is stable I am going to remove the on-board battery holder, LOL.

CPU
Sound

Ok, it's a good spot to start looking tomorrow. Will wait to see what johnwartjr posts too.

Ok, sorry for the long delay but was finally able to go get thermal paste today and took out heat sink (as circled in photo a few posts up), cleaned it and the component (transistor?) and re installed. Same issue as before, sound stops after 5-10 minutes. Sound check does't work in diagnostic mode (just cycles thru sounds, but you hear nothing). I touched heat sink and transistor after sounds stopped, didn't feel hot to me (a little warm). So what's the next step?

Thanks!

And after 25 minutes of being turned off (but plugged in) the sounds is back.

There is a dial on the sound board (lower right side of picture above). I assumed it was to balance between sound effects and voice.

I also should point out that i pushed in the speech diagnostics switch on the CPU board itself (versus the sound test that can be run via the buttons on the coin door). All the speech sounds appear to be there. When I attempt to do the same test after sound has been lost, nothing but some very faint squelches.

Yeah, that's the master volume. I have played with both and during the first 10 mins, all sound and speech is perfect.

So after sound cuts out, you can still barely hear it, just super duper faint. If I crank up the master sound volume to max the humming gets much louder and the sound gets just barely louder. Turning the sound up also causes the static over the speakers. Will check in the morning when its cooled back down to see if static happens when its not overheated.

Can you clarify how to jumper J10? I get what a jumper is, but do I jumper between pin 1 and 9 or what? Thanks!

Cheddar pointed me to this: http://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11#Isolating_the_CPU_Sound_from_the_Speech_Board

Trying W10 now...

Ok, after a few months I finally got an hour or two to focus on the sounds issues again. And went back to the basics. I was inspecting the MPU screws to insure they were tightened down and no shorts were occurring when I discovered that I was missing three screws and had a fourth one that was barely hanging on. After installing and tightening them all down the problem appears to have gone away. I tried at first to just bypass the sound board and had no issues. Added sound board back in and still had no issues after letting it run for about an hour.

Thanks for all the help!