Hi Imran,
It's close but with a few notable differences, some that could be the product of half-baked repairs and others that are inherent design differences on the board. For example: the fuses on the low-voltage circuit are absent and the contactor component numbers in the silkscreen are different than the diagram.
I spent another few hours trying to build out a schematic of the contactor actuation circuit yesterday, going as far as to remove the board from the machine to do so, but I'm not having much luck decoding it. I'm a mechanical engineer and am in over my head trying to figure out how the board logic works.
I've resolved for now to get the machine running using a potential start relay and a standalone contactor to drive the existing motors. I'll leave the existing guts of the machine powered off and only re-use the function selector switch by disconnecting the power leads from the board and wiring the output of my "drive" directly into the switch. I can't see much downside to doing this besides the marginal loss of safety features (my brake is already toast, so I'm only losing the microswitches and pushbuttons conveniently located at each function's station).
If this works I'll document it here as a last resort for other folks. It shouldn't be complicated or expensive to do. Maybe if I find some time in the evenings I'll wire up a microcontroller and some simple code to re-incorporate the low-voltage functions. I think my main board has breathed its last though. A 25-year run isn't too shabby.
