i own a ampeg b2r that has been trouble free for the past 6 years or so. @ my last rehearsal it would cut out randomly, but then come back after like 10-20 seconds or so. The amp isnt shutting down, all the lights stay on, and it's still getting a signal to my compressor and korg tuner, the only thing not functioning is sound coming out of the cab. any ideas? i dont know where to start.