yamaha T100 low output on the gain channel only

[rosssurf]

Another guy here with the same/similar problem. The gain channel is barley audible and is distorted and blatty. I have another T100c right next to this T100c and have swapped all tubes into their relative positions and it funtions as it should. So tubes are not the issue. The controls on the gain channel work as intended.
I plugged into the FX return and the problem is the same. Can anyone tell me specifically what part i need and its location? Thanks in advance.

[Enzo]

Who says you need a part? Could just as easily be a connection or a broken copper trace.

Since every part in a channel is involved with making teh sound, it could easily be any of 50 things. Your job is to use classic troubleshooting techniques to narrow it down to one circuit. The odds that the exact same thing is wrong with your amp is tiny.

[rosssurf]

Who says you need a part? Could just as easily be a connection or a broken copper trace.

Since every part in a channel is involved with making teh sound, it could easily be any of 50 things. Your job is to use classic troubleshooting techniques to narrow it down to one circuit. The odds that the exact same thing is wrong with your amp is tiny.

Thanks Enzo, I was a bit hasty in writing my question. I see now the opto's you referred too in your post (post #7) I am not that familiar with this type of component. I would like to replace these and see if that helps. I am not seeing an identifying # on these two parts. Can you steer me to the correct value or size? I am not even sure those are appropriate question for these components.