before reading any below, the search wipers spin all the time when you turn on the game, right? If the search index unit is powering and stopping the wipers, that's a problem.
assuming the search wipers are fine, credits should get removed at a steady cadence.
the start relay releases and re-energizes itself? What should happen when there's no credits is:
- you manually close the start relay and it keeps itself powered
- when the start relay first closed, the timer cams index and mixer latch coils power and the game starts it's cycle
- when the timer cams rotate around 45 degrees (typically ... I don't have timing diagrams for big time yet), the start relay unpowers and stays unpowered
- cycle continues until timer cams rotate 180 and lock
- sometimes units continue to step up, but soon stop
once the start relay unpowers, nothing should be able to repower it is switch D on it is opening correctly. D is the top switch.
did you mean the replay reset relay is powering and unpowering while credits are being removed? That would cause irregular cadence. The start relay is the middle one in the 5 relay bank, the replay reset relay is on the bottom.
got a voltmeter or jumper wire?
with no credits on the game, connect one end to wire 30 on the transformer. Wire 30 is the one that attaches to a bottom lug then loops up to a top lug. Connect other end to the middle blade on the left switch on the replay register (wire 48-2). Flick coin switch and see if the game responds.
If it does:
- turn off the game reasonably quickly to avoid holding some solenoids powered too long.
- move jumper end from replay register switch to CU 3A switch with the black/yellow wire on it (other wire on 3A is green/black ... same wire that was on the replay register switch)
- try the coin switch. If it works, search index 17B isn't closed well. If it doesn't work, CU 3A switch isn't closed well
game on. Stick one probe on wire 70 on any handy 50V coil or the 50V fuse. Put other probe on wire 48-2 on the middle blade of left replay register switch. Got 50VAC? If yes, hold down the coin switch. Still have 50V?
if you didn't see 50V on wire 48-2 or the 50V dropped way down when holding down the coin switch, then CU 3A or search index 17B is making no/poor connection. Move probe from 48-2 to to black/yellow wire 83-3 on the CU 3A switch to see what the 50V is doing there.