Hello! I'm trying to fix a friends amp. It's a Pignose 30/60. He bought it about 6 months ago and worked fine, and sounded great. Perfect for band practice. He went to turn it on a couple days ago and it made a loud noise for about 2 seconds and tripped the circuit breaker. It doesnt have a fuse. I can't find a schematic. It's not one of the battery powered amps, and I'm guessing its from the 70's. I'm not a total newb, I've built a few tube amps, and modded a few pedals, but I don't know much about SS stuff or how to troubleshoot. Does anyone have an idea what it could be?  Thanks,  Denny