PeteB wrote:I will try, from memory, but it may be better to wait if he decides to pick up the thread.
As I remember, there was one working channel between the two units. There was a leaking electrolytic cap in that unit. His son removed/replaced those, and a couple other caps which did not measure well with a small capacitance meter.
The amp does not have a typical output stage, but there was a signal on both channels, but output on only one. The bad channel showed a clipped signal at a low voltage when tested with a sine wave. neither channel reached anything like close to the rails. I don't think there was any diagnosis after that, not that I was a part of.
I believe his son either guessed, or read some posts on the web, and started replacing parts a couple at a time. When the formerly bad channel started to work, I believe he simply replaced the same parts in the right channel.
The other unit is not completely "dead", in terms of power supply, but no output on either channel, and no attempt at repair. That is all I can remember.
Another observation, to me personally, the output on the one working channel did not look like a perfect sine wave as the test signal was increased in amplitude, and a square wave was hardly crisp. In use this would have given it a very warm sound, like a soft clip circuit.
First thing to do is unplug the rails and confirm the psu.
After that depending on serial number on the outlet posts check / disconnect the clamp board
knowing the serial number of the unit or cards would be useful for further info.