Sounds like you have one good amp and one bad one. Time to troubleshoot the bad one. I just went through this on a 2270, and I am not much help. It was a lot of trial and error removing and testing parts. Turned out I had installed the wrong transistors in the diff pair. If you have recapped that board or replaced anything, check your work first - proper components, polarities, solder joints, etc. if all is good there, you might have to start testing transistors starting with the outputs and work back. I think the blue wire is the left amp, but check just to be sure.
