I pulled a dumb move. I was wiggling a bad interconect, and its ground touched the positive speaker terminal, creating a spark. Don't ask how. Yep, the amp was on. Counterpoints are known to be touchy on this, blowing output stages. This is a 220, so it does have output protection circuitry. It engaged when this happened. Green LED went to red.
I powered it up with a variac, it did un-mute and there was not excessive DC offset at the output terminals. The output and rail fuses are good. The gate resistors are not fused, and the diodes read good.
However, when I push the voltage past 65 volts or so, there is quite a hum from somewhere in the board area. I think I localized it to the relay(s.) I removed the fuses from the channel in question, and the hum is still there. It is pretty loud, and increases with the line voltage.
Is this simply an issue of hum since I'm using a variac for the PS? Or do you think the problem lies deeper?
Thanks for your time.
Cory
