Tried desperately to figure out what is wrong with my PAS, I recorded some of my observations; https://www.youtube.com/watch?v=VjBNBo2Anrs
Be warned, the video gets loud in places. I also found that if I plug a cable into the MIC socket and touch it, the pulsing gets faster. Putting a multimeter across it causes it to become much faster. It's a weird pulse because it doesn't show up as expected. I thought it would look kind of like ^-^-^-^- on the timeline but instead it looks like ^-v-^-v- as in, it dips into negative values every other peak.
Any ideas? Is it worth making a thread on it? I won't be too upset if I have to hack away the circuitry for that input as I don't use it. I have tried to trace it back and can find both an LM3080M and an LF347M pretty much directly connected, not sure past that point. Perhaps I could cut the power to these (as it would be fairly easy to re-connect) and see if it kills the pulse and clears the sound. It almost seems like the MIC input is interfering or even somehow feeding the output back into the amp. Removing the jumpers connected to the MIC socket do nothing for the problem, I tried.
I wasn't even doing anything bad when it broke, I was playing ROTH and fired my gun - this is incredibly loud sometimes in that game - and the sounds distorted and remained that way. I guess it pushed something just a bit too hard. I only had the volume at 50% at this time too, so I wasn't exactly being horrible to the amp or anything.
Kind of tempted to just stick it at max volume with a bass test running on a loop or something, then just wait around and see if something goes pop. I'm really running out of ideas otherwise and the Mic circuitry is tied to the power rails too closely to make it very traceable.