Okay, we're making progress. As you have to reset the circuit breaker, we know that the amp is drawing too much current, and that the current sink is downstream from the standby switch. The fact that you didn't suss this out on your own indicates that you are not an amp technician, and should seek out help. If you know of a competent technician, take the amp to him. Alternatively, where are you? I wouldn't mind looking into your problem, but I doubt that you are in western Oregon. My first guess is that the filter cap(s) are leaking, drawing excess current and causing the breaker to trip.