GK 400RB head problem

[gonzoknife]

My friend has a GK 400RB bass amp that the audio will cut out on sporadically. We'll be playing and then the sound will shut off. Powering off and then on again will usually bring it back. It isn't losing power. I've done some basic troubleshooting on it. Checking voltage per the schematic, etc... but I'm at a loss as to where to look next. The boards and traces look good. No obvious bad or burned components.

I haven't been able to recreate the problem mainly because I don't have an opportunity to play for a while to make it happen. I'm also much more familiar with tube amps so my ss knowledge is a little weak.

Any ideas as to why the audio would cut out and require a power cycle to work again?

[Phostenix]

It looks like that amp has Send & Return jacks, right? Put a patch cord between those jacks to make sure they aren't causing the problem. You said that the traces looked good, but didn't say you've inspected the solder joints. Go over the board carefully & look for bad or cracked solder joints.

[gonzoknife]

I'll try the send/return idea. I did check the soldering joints and didn't see anything.

I still think because it works intermittently it could be heat related.

[Viper]

Does the amp have a thermal protection circuit? That would cause it to shut down at certain temps.

[Enzo]

Heat problems don;t usually operate on short time scales.  if it heats up enough to turn something off, then it has to cool enough to clear the problem.  SO if it is cutting in and out with any rapidity, then it is more a connection than a thermal issue.

[J M Fahey]

To begin with, follow the suggestion posted above. The minute it cuts off, plug something (instrument, MP3 player, whatever) into the Effects return jack , without turning it off. At least you're "splitting your amp in two" and knowing whether the problem lies after or before that point.
You can also hit it with your open hand, listening to clicks, crackling sounds, etc. Not very technical but time honored. Good luck.

[gonzoknife]

Thanks for all the suggestions. I've been otherwise occupied so I haven't check in recently.

Now I just need to find the time to play it enough to recreate the problem! That may be harder to do that fixing the amp.