I would open the unit(bottom panel?) and check/reseat connections between the circuit boards(isn't it 1 board for channels 1-8 and a second board for 9-16?). Pretty sure that the 1-8 circuit board gets all its voltages from the 9-16 board(IOW, no direct connection to the PSU)
If that doesn't help, maybe check with an avid-approved service like allproelectronics.com for advice or repair info
