Ok guys, i've been working on this Bally MPU -35 board for a few days and it's driving me nuts.
The original Frontier ROM set was not working properly, EPROMs (2716s) were bad, so i converted the board to 2732, so that I could use the EPROMs I had in stock.
Now I can get the board working on my testbench (JAMMA switching PSU) with +12DC, +5DC and ground.
I get 6 flashes on the LED and all seems fine.
When I put the board in the cabinet, the LED gives the initial flash and then it halts.
Put it back on the JAMMA-rig, and it works again.
What in the lords name is wrong???