I have a Bally converted cabinet which I rebuilt the Autoslot CPU board on a few years ago after a bad battery leak and ended up stripping the board to replace over two dozen breaks, two IC's and and the output transistors for the display and dump/burn a copy of the EPROM. Initially it worked fine and I was getting activity out of the coin diverter, electronic counters, the hard counter and for a one-line nickel machine you could get it to pay out a few times in half an hour, even hit a jackpot so it was consistently entertaining to play. Then after a few weeks it seemed like the payout odds just suddenly sucked. You could put $20 in nickels into the thing and it would never pay out more than once, if at all. Likewise the electronic counters stopped and are stuck at 000 000 but the SRAM seems to be keeping its contents and game state on a power hit so it's not another bad chip or battery that I can tell.
The other less pressing issues is that the door switch tests fine but the CPU never detects the door as open (EG: pressing hopper and CPU reset on a coin tilt should hold the hopper until you you close the door but it doesn't and starts spilling nickels everywhere as soon as you reset) and while I have the service manual for the Autoslot conversion kit the wiring harness and terminals do not match the diagrams. Likewise a lot of the diagnostic information also does not match.
This unit has the I/O board with the solid-sate relays and not triacs. At least one has failed and been replaced so far in the hopper circuit.