PS03 Rev 1.3 intermittent -30V?

[mikeycot]

I have had the following issue for several years: my J99s and especially A12s will often "go to sleep" after not receiving a hot signal for a while (ie after sitting idle for hours overnight or between sessions). I also have a pair of N72s in my chassis, but they've never exhibited this issue. It seems to happen to one preamp at a time, never more than one preamp at once that I can remember. The signal will become extremely low in level and gated/sputtery sounding. Giving the input gain a quick boost, then turning it back to normal level will make the offending preamp return to normal operation.

I've had a tech looking into the issue, and it seems that sometimes the negative voltage at the op amp will be very low, and cranking up the gain momentarily seems to make it return to normal, like I've experienced in my use. He's seen the problem once on one of the A12s when all of my modules were connected (2xN72, 3xA12, 2xJ99), and another time with only one module connected - a 4th A12 that he was troubleshooting for a different issue, which wasn't connected to the system at all before that moment. We suspect that the problem is with the -30V from the power supply and wonder what we should be looking for.

Thanks!
Mikey