Hafler 220, one channel out of sync HELP

Greetings, My older Hafler is showing some age and wear one of my channels is not operating at full capacity. I do get some sound out of it with a bit of distortion adn it fdoes respond to adjusting the volune. Changed the wiring witht the preamp and speakers around to make sure it wasn't somethimng easily replaceable but it's starting to look like time for Hafler salad surgery. Not really sure what to look for here, a new fuse change the transistors. Open for sound opinions and advice. Thanx much and have a great day, Terry