Quoted from sbmania:I have a Disco Fever exhibiting some weird behavior. It boots and plays fine, but occasionally when it boots up the 1st player display shows 2 zeros and the ball in play display continuously counts up from 1 through 40 or so. Almost like it is in self test? If I turn it off and on, it will usually boot up and play fine except when the high score to date lights up, the 1st player will go blank and display nothing at all. The game will still play normally though. If I turn it off and on a few times, it will eventually go back to normal and display the correct pre-set high score to date. It never actually loses its memory permanently.
I replaced the 5101 and it seemed to fix it for a few days, but the problem is back again. I checked battery voltages with power on and off and they seem correct so I don't think the diode is shorted. Any other ideas?
I think you are describing the MPU thinks the coin door diagnostic step switch is stuck closed.
First off, just check the coin door diag switch itself. You can also try unplugging the coin door switch from the MPU (4pin plug, upper left). If the audits still scroll quickly with that plug off, then the issue would be on the MPU. If unplugging that connector immediately stops the audit scrolling (counting) then focus on the wiring to the coin door buttons. Not leaning on the grounded coin door, button stock down, etc.
Woolwich Township, NJ
