Sometimes it's a cascading problem, a resistor here, a rectifier there and pow. With my M-500, I was loosing a rectifier in the feedback loop that controls the power rails. The voltage would just keep creeping up. The first thing it did was take out the caps (they were old and weak). I recapped the whole unit, and still had a problem, but the caps were strong enough to get me through the troubleshooting. You might give RichP714 a call (or PM), as he's the expert on the M-500(t) as well as the M-1.0t.
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Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer