Vintage Synth Repair

Hi group,

I recently bought a first generation DX7 for $ 50. Problem on startup: sometimes starts up OK, sometimes keeps looping, sometimes seems OK but actually frozen. 
When it starts up OK, I found only garbage in the internal memory, but it works with the cartridge. It does not memorize my settings, and main output seems dead (headphone OK). I've suspected and replaced the battery cell.
I was able to run the self tests up to test #5 (analog inputs), but I have no foot controller to complete this stage.
I checked the PSU and the voltage source on the main board (+2.5V, +7.5V and +5AV) and everything is OK. 
I suspect a signal is missing on the sub-CPU (6805), or a defective RAM.
I picked up the schematic and the service manual on Dave Benson's site, but it seems to be altered after page 20. All other services manual I found on the web has the same issue. Does anyone have a full copy of it?

Thanks,
François