[Jack[_11_]]

This is a great piece with one little problem. Often, when switching the
unit on, the left channel is out, no sound. Turning the volume up always
kicks it in. Often the volume has to be turned up severely to accomplish
this so I tried doing it with the speakers switched off. Switch off
speakers, turn volume up to max, turn volume down to min, switch
speakers on, turn volume up a bit and the sound is back in both channels.

In addition, after getting both channels to work, after 10 to 20 minutes
give or take 5, the left channel goes out again.

This behavior lead me to suspect the volume switch, so I flooded it when
switch cleaner, but to no avail. Problem persisted. Next I checked all
the cold solder joints and found one that was loose. I hot soldered ALL
the cold solder joints. Problem continued. Today I used some cables to
switch the PRE OUT channels into the POWER IN channels, left to right
and right to left. The next time the problem cropped up it was the RIGHT
channel that went out. I interpret this as the problem being is in the
left main amp section. Given the behavior described above I can only
surmise that a rise in voltage in the main amp produced by turning up
the volume with the speakers turned off somehow corrects the condition
causing this problem, but at the moment I don't know what this condition
might be. I assume that with the speakers turned off there is not a lot
of current flowing in the main amp when the volume is turned up, but
that the voltage is increased. As I write this a dawning suspicion
presents itself and that is the problem might be with a transistor. At
any rate it is an interesting problem and I am about to dig out the
schematics to see what I can see. My knowledge of electronics is not
that deep, mostly stuff I picked up as a kid and built upon when needed.