[Major Debacle]

William Sommerwerck wrote:
I would not completely rule out the possibility of a bad speaker relay.

That was the easiest thing to try so I tried it first and that seems to
have done the trick. I used a small strip of 600 grit sandpaper to buff
the contacts and the receiver has been playing for over 6 hours without
dropping the left channel. Usually it would drop out after 15 to 30
minutes, guaranteed.