JITB was working properly until this past weekend. I bought a 2001 and moved JITB over in the basement to make room. That's when the problems started.
Here's the problem: at the end of a ball (or during the reset cycle), the bonus stepper unit on the bottom of the playfield cycles endlessly. If there are drop targets knocked down, it will first score them correctly, and then keep re-scoring them endlessly (despite that its runout switch is working; more on that below). Somehow the machine never goes from the "bonus count" cycle to the "reset the drops and kick the ball to the shooter lane" cycle.
While the bonus stepper is endlessly rotating, if I reach down and remove the ball from the outhole, the bonus stepper unit will complete its cycle (honoring its runout switch, which is gapped correctly), the drops will reset, and the outhole kicker will kick. I can start a ball and play properly (until it's time for the drops to reset, either mid-ball or end-of-ball; then the problem manifests itself again).
I have been struggling with whether this is a bonus stepper problem, an outhole problem, a relay problem, or a score motor problem. Here's what I know about each:
BONUS UNIT: I know that it is stepping properly, i.e. its snowshoes make clean contact, because it accurately scores downed drop targets. I know that its runout switch is working, because it stops correctly when the ball is removed from the outhole. The bonus unit is a bit mysterious to me as it's scattered through the schematic. I've included several snippets where it appears.
OUTHOLE: I know the outhole switch works, because when I remove the ball from the outhole, the bonus unit stops cycling and I get a clean reset. I looked at the switch and confirmed that both of its contacts are operating correctly (i.e. it's not half-working). Furthermore, I know that the kicker is working because when I remove the ball from the outhole, I get a clean reset which includes an outhole kick. The kicker has scraped my hand more times than I'd care to admit while I've been manually actuating the outhole switch during all this futzing.
RELAYS: I have confirmed the gaps and action on relays E (ADD BONUS UNIT RELAY), F ("E" RELAY DELAY RELAY), Q (BONUS SCORE RELAY), and QB (GAME OVER RELAY).
SCORE MOTOR: I have confirmed gaps and action on 1C, which fires the outhole kicker. And, dang it, the outhole kicker *fires* as part of the reset sequence, once I remove the ball from the outhole.
Any advice is appreciated.