Rivera Bonehead channel switching problem

[bsco]

Somebody just dropped off a Rivera Bonehead 3 channel amp and have the problem of the channels actually switching but no audio from channel 2 and channel 3. Channel 1 works fine. I can't locate a schematic for this monster...Does anybody know where I can get one for this unit??? It is going to be tough fixing this amp but it will be a nightmare without a schematic....In the meantime I'll keep searching for one but if somebody has a link for one it would be much appreciated....
Cheers,
Bernie