Trying to repair a 414. The faults seem to be only with Channel 1. Anything I plug into the mic/line in socket for Channel 1 comes through at a very low level, even with the trim all the way up. It is too low to activate any of the LEDs in the meter, and to make a passable recording. If I use an adapter cable and plug the same instrument into the balanced mic aux input on the back, the meter will read a level (but quite low compared to the other channels), and I can record a passable track on Channel 1, but it is at a much lower level than the other channels. When I go to mix down my finished recordings, there is no output at all from Chanel 1 when I click on the monitor out switch and use the monitor out RCA outputs. If I click on tape cue, I then get Channel 1 from the monitor out RCA outputs. I've had a look at the internal PCB and see no obvious signs of component damage. Any suggestions as to where I should start looking, or what components I should start replacing?