Hey peyemp,
Man this module has 7 pc boards! What a mess.
There is a pc board on that rear-inner plate. That is the power supply/regulator board. Are the loose leads gray or colored (colored being the PS sends to the compressor mother board)?
The board gets fed 24vac (2 windings), and +-18vac (center tapped).
From the top down on the outside edge of the PS board I have:
-2 green wires (soldered to the same pad)= +24vdc grounds (both going to the audio mother board)
-2 red wires (soldered to the same pad) = +24vdc (one wire going to the main back panel connector, the other going to the audio m-board)
-1 black wire = -18vdc to audio m-board
-1 yellow wire = +18vdc to audio m-board
-1 green wire = bipolar ground to audio m-board
If the loose wires are gray, they are the different audio and control sends that go to the main back panel connector. There should be a block diagram on the top panel of the module that has the pin-out of that connector.
On my device, it appears that the 4 boards in the edge connectors serve specific purposes- "compressor side chain " (discrete), "peak limiter side chain" (discrete), "expander/gate side chain" (discrete), and "variloss type II"? (monolithic op amp board). See if your other boards fit that description.
You can remove the top and bottom panels of the module, and the mother box to at least test around on the top board (with everything plugged in). Like you said, you can't really bench test this unless it is docked with the mother ship.
If what I'm talking about seems to correlate with what you have, I might have some diagrams that will help.