I have a Peavey CS-800 "C" on my bench, that was brought in not working - owner stated one side gets hot, the other does nothing, and it blows fuses.
Well anywho - I found several problems with it, shorted trannies, cold solder joints, an open resistor, a resistor that was never soldered, connectors on the wrong terminals, one connector the wrong way around, burnt traces on a patch board??? (yeah, that last one had me worried... almost declined the repair) etc, etc....
In its current state, all of the important issue have been corrected, and the amp is stable (no input, no load, all controls at min or off), with or without my dimbulb, powers up just fine, the fan kicks on low, the high speed fan switch works, the heat sinks stay cold.
But... with the dimbulb, "and" a speaker connected to either channel's output, it buzzes/hums loudly (through the speaker), and the bulb is as bright as it would be with a short.
All transistors are fine, all diodes pass, all caps pass, all voltage rails are at correct values, all op-amps pass, the crowbar is fine, etc... The only thing that settles it back down, is firing it up without a speaker.
Voltage at the outputs swings a little when it's powered up, but quickly settles at 0.00 volts DC.
The problem is not exclusive to a side, and only happens with a speaker connected to either channel's speaker terminals.
My guess is the filter caps, but I'm at a pause, because I'm not ready to shell out the loot for new ones quite yet - because of how it behaves without the load.
Well anywho - I found several problems with it, shorted trannies, cold solder joints, an open resistor, a resistor that was never soldered, connectors on the wrong terminals, one connector the wrong way around, burnt traces on a patch board??? (yeah, that last one had me worried... almost declined the repair) etc, etc....
In its current state, all of the important issue have been corrected, and the amp is stable (no input, no load, all controls at min or off), with or without my dimbulb, powers up just fine, the fan kicks on low, the high speed fan switch works, the heat sinks stay cold.
But... with the dimbulb, "and" a speaker connected to either channel's output, it buzzes/hums loudly (through the speaker), and the bulb is as bright as it would be with a short.
All transistors are fine, all diodes pass, all caps pass, all voltage rails are at correct values, all op-amps pass, the crowbar is fine, etc... The only thing that settles it back down, is firing it up without a speaker.
Voltage at the outputs swings a little when it's powered up, but quickly settles at 0.00 volts DC.
The problem is not exclusive to a side, and only happens with a speaker connected to either channel's speaker terminals.
My guess is the filter caps, but I'm at a pause, because I'm not ready to shell out the loot for new ones quite yet - because of how it behaves without the load.