Orange TH30C channell switching problem

[Steelwitch]

Hello! A customer brought in a th30c combo with faulty switching. I can't seem to track down a schematic, could anyone provide one? or at least a description of the switching circuit in these amps? Thank you!

[Pedro Vecino]

Here is the schematic:

https://music-electronics-forum.com/...3&d=1521589896