Humming Noise

I have a pair of Don Cochran mono amps. One of them is causing the humming noise to speaker (B&W 801/3). I think one of the caps is leaking but not sure. How do I fix it? Don was out of business. Where do I send the unit for service? I have manual user and schematic. Please help. Thanks so lot in advance.

Before you decide your amp is defective, try these experiments:

1. turn both amps off. UNPLUG the amp that is not humming. Turn the "humming" amp on and see if it's still doing it. If not, then you need to "star ground."

a. try switching interconnects at the amplifiers to see if the hum switches sides.
b. turn the humming unit off, remove the interconnect, turn it back on. If the hum is gone, the problem is not in the amp.

3. try phyically moving the amplifiers ( bad one to the position of the good one ) to see if the hum changes.

Best of luck,
The first step in this diagnosis is to disconnect all inputs, power back on, then check for the hum. If you still have it then try an AC polarity change &/or temporarily lift the ground with a cheater adapter. If all that fails then you do very likely have an actual problem. Get out your oscilloscope & check the AC ripple on your supply rails, comparing one amp to the other. Suspect the caps at that point if there are radical differences. It could also be a rectifier. Mod guru Andy Bartha can probably take care of this for you.
Andy Bartha Mods
4680 SW 74th Terr
Davie FL 33314
try doing a search on hum and you'll see that it is most likely a ground loop - easily fixed.