First thing you need to do is try and determine if the problem is in the
pre-amp stage or power amp stage. Looks like you have a good break point at
R500/R550 for one channel and the equivalent point for the other channel.
Manually swap the pre-amp stage to power amp signal between the left and
right channel at those resistors and see if the symptom stays with the right
channel (power amp problem) or moves to the left channel (pre-amp or earlier
problem). Note I am not talking about what Sony calls the pre-amp
transistors in the power amp stage as shown on the schematic, but the actual
pre-amp before the power amp board.

I would also suspect any electrolytic capacitors in the signal path, like
c500/550 for one due to the extreme age of the unit. C505/555 would also be
suspect due to its location in the feedback path.

Due to the age I would probably start with the capacitor ESR meter as
capacitors commonly go bad with age. There are not that many to check and
it owuld rule out one common failure source.

David

Arvid Puschnig wrote in message
y.telekom.at...

"Arvid Puschnig" wrote:

Ok, I'll put it up the next 2 days.

Ok, here it is:
http://www.sbox.tugraz.at/home/a/arvid/TA-AV501R/
It's the schematics of the Speaker Board and of the Power Board.
Please tell me if file sizes and quality are ok...

arvid