I have a 1977 Bally Eight Ball that I just bought. It was missing the MPU when I bought it and appeared to have been sitting around for many years. I purchased an AllTek ultimate MPU and I installed it according to the instructions. The game will turn on and I can enter the self diagnostics mode with no problems. I was able to get all the feature lamps fixed and I ran it through the solenoid tests. All solenoids work with the exception of the knocker and one chime. The coils on these two are bad and the wires have been cut. I have ordered the coils and transistors for these. I ran the stuck switch test and it shows that switch #2 is stuck. I inspected the switch and it is not out of adjustment. I removed the wires to that switch and the machine still shows that switch is stuck. Figuring this would not stop the game from running (?) I finished the game adjustments and book keeping and attempted to start the game. The intro chimes play fine, the flippers work (switches held closed) but when it gets to about the point where the ball ejects, some spotted lamps light just as the relay on the solenoid driver clicks and the game freezes and the flippers fall. From this point the general illumination lights are lit, some feature lamps are lit (spotted) but nothing else seems to work. Points cannot be scored and solenoids will not work. I try to enter self diagnostics from here but that will not work either. I turn the game off and back on and I get back to where I was with attract mode working (racked balls light up in sequence as normal) but as soon as I try to start a game it freezes again. While frozen, I checked the voltages at all test points on the power supply and solenoid driver and they all seem to be fine. I can also enter self diagnostic mode again.
The switch that diagnostics shows as stuck (#2) has a diode and also a cap across it (I do not see it on the playfield diagram). I was wondering if this switch problem could have something to do with the game freezing?
I did plug the MPU into another game and it works fine in that game. I also tried the memory clear feature but that did not change anything.
I have also ordered all the pins and connectors to replace all the female connectors going to every board. I have also reflowed the header pins on the solenoid driver board but not the power supply board yet.