Hey guys, I purchased this nice amp about 2 years ago. It seemed to work fine. The previous owner had rebuilt most of the boards with Nichicon caps. What I have noticed now is that it will fire up fine, but after about 10 minutes, the left channel drops significantly in volume. The primary filter caps have not been replaced. I'm aware of the common fault of a coupling switch problem. I jumpered the preamp to amp RCAs with the coupling switch in the disconnect position. The same thing happens. My next step will be to criss cross the jumpers and see if it's the amp or preamp. Has anyone had this happen? If so, what would be a possible problem? The balance pot and all other pots have been cleaned with Deoxit. I'm not sure what to do to track down the problem. No, I don't have an oscilloscope. Any help would be appreciated.