Tech: Biamp 2442 Mixing console

Archived from groups: rec.audio.pro, sci.electronics.repair (More info?)

I have a Biamp 2442 board that has a hum in the aux/mon/echo returns.
Doesn't appear to be in the pwr supply, all rails show negligible
ripple. When monitoring thru the headphone out w/no signal in a hum is
present when these return pots are turned up when each bus is solo'd.
Found a few 10u BP coupling caps that needed replacing, but the hum is
still there. Must be an op amp that is common to all 3 busses. I don't
have the schemo as of yet but the way its going I will have to track
one down. Anyone seen this prob on one of these?

Thanks
Travis