PC4100 Problem

I just purchased a used Precision Power PC4100 and it has the oddest problem. The front channels will only seem to play in some sort of pseudo-mono mode. I've plugged my laptop into the amp to make sure the problem wasn't with the head unit or rca's. I've unhooked the speaker wires and put a volt meter on the outputs to make sure the problem wasn't a short in the speaker wire somewhere. No matter what, I get the same problem.

When I try to fade left or right, the volume goes down slightly, but both speakers still keep playing. I'm guessing this is some component failure in the amp itself, although I don't know electronics well enough to find it.

Has anyone else experienced a problem like this? Does anyone know a place to send these old school amplifiers to have them repaired?

Thanks.
 
There are large resistors behind the RCA jacks. Are they within tolerance?

Disconnect the RCA cables from the amp before checking them.

Thanks for the reply. I'll check that once I get around to removing the amp from the car.

I noticed today the problem was intermittent. For a while the channel separation was fine, but then it went back to the odd mono mode.