I'm currently trying to repair an old Sony TCD-D7 DAT-Walkman.
It suffers from unbalanced audio output. The right channel is much quieter than the left one during playback.
The headphone amplifier circuit of it looks like this:
Full schematics can be seen on pages 18 and 19, part names on pages 27 of the service manual.
Unfortunately, I have not been able to identify a faulty component. Maybe there's something broken within one of the ICs. Now I wonder whether there's a way of modifying the circuit itself to increase the output volume of the right channel, as a somewhat "hacked" solution.
As far as I can tell, there are two inverting opamp circuits in this circuit, one for each channel. Changing the resistor values of R227 and R127 respectively should hypothetically change the amplification factor of the whole circuit, no? When I tried to do so, nothing happend apart from strange noises coming through the output.
What have I done wrong? Is there something I have missed? Any other ideas on how to modify the output volume?