Yamaha R8 Problem

I have a Yamaha R8, works fine except for volume and left channel not working.
Turning volume knob has no effect, except for maybe a pop here and there.
Pressing the "Simulated Stereo" button introduces normal behaviour.

Does anyone have an R8 schematic?

"rolibark" mentioned he had an R7 schematic, but the link is broken.
 
Pressing the "Simulated Stereo" button introduces normal behaviour.
That would be SW302 on the schematic:

Yamaha R8 01.jpg