Hi Mosiqaar
A group I've been involved with used either the same board -or some model close to yours.
It had an intermittent on one amp. Because I am a Electronic Tech., I took it home to check out the problem. When I lifted the mixer out of its case, I noticed a clip-in fuse in the power supply section had one end of it just resting on the fuse holder. I snapped it back in-end of intermittent problem. When I was working on it, I recall the multi-pair cable running in the outer case to the power amp. Thats why you can't see the connection between the mixer and the power amp. When we went to a hall for set up,
if a small table was available, we just laid
the mixer amp on the table, removed the lid,and began our setup. The lid as part of a 'X'table works fine, but an 'extra' small table in the hall is quicker. I don't recall having any manual/schematics around when I had the intermittent problem-so I don't have
any other info on your unit.