I just got an A77 up and running. I'm able to monitor both channels but when I switch the input to NAB there is a hiss and hum in channel 1. It makes no difference if the tape is playing or not. I've given the heads a good clean, tried cleaning the selector switch and played different tapes. None of this has affected channel 1 (though channel 2 sounds great) so I'm assuming it's not a record/playback issue. Hoping someone can help me.
Best,
David - Just a Revox A77, for now.