If both left channels do not work, that might be an easy fix. The channels are independent of each other, aside from a few connections in the preamp section. You could be dealing with a bad combine switch, or bad configuration switch. Thanks. Didn't know I got any replies. I thought I'd get an emai...

It works in bridged using the left + and right - I cleaned the board with iso, soapy water, and rinsed it. After drying it in an oven the left - came back to life but not for long. Does this sound like a bad solder somewhere down the line? Can I troubleshoot it with a multimeter only? How much would...