rise to glory

Tried connecting the effects loop, didn't make any difference unfortunately. Looking at the valves they have a yellow orange glow top and bottom and blue purple centre, which correct me if I'm wrong would indicate they,re still fine. The tech explained that the bias was miles off when he went to set up for the new valves and that he had trouble getting it to an acceptable level, but got they're eventually.

Bias drift may indeed be the issue, I do use a pedal or two so it's wholly possible. Would you be suggesting that the pedal power supply is to blame. Come to think of it it is just a variable voltage adapter, probably not good practice?

Cheers for responses, feel like I'm learning something