I've had a bizarre problem with those Peavey combo amps...not sure if this is normal, but it's happened on 3 that I've owned:  the reverb seems to just randomly start screwing itself.  Either it stops working, or it just starts buzzing horribly.  Naturally, this stops at the very second that I bring the amp into the shop when I'm trying to explain the problem to the repairman.  Do Peaveys just have crappy reverb pans or is this just my luck?  YMMV.  I gotta admit...I always did like their distortions.