I would check the power transformer. It sounds like it's beginning to vibrate at the 60 cycle rate of the A.C. line after it gets warm. Try tighting up the screw and tap set at the corners of the txfmer. Or mabe the windings have become loose, in which case disassembly of the device (transformer)will be needed to remedy the problem.
I must caution tho,if you arn't confortable in pokeing around your amps inards, I would take it to a repair shop and ask them to look at it.
[This message was edited by Bill Crook on 03 February 2002 at 09:09 AM.]
