I recently purchased this machine, and although it had not been serviced in a long while, it was actually working quite well. The one exception is that the bonus scoring would sometimes stall upon awarding the last thousand points and hang up for a while before shutting off and kicking out the next ball. I figured that was related to a dry and dirty bonus stepper unit, so I decided to service that item. I removed the playfield and took out the bottom panel to get to the bonus stepper. I checked, cleaned, and added a little dielectric grease to it, and confirmed that everything seemed to be stepping nicely. While the board was out, I cleaned the relay switches, and gently tightened the screws on the switch stacks that were accessible.

(That may have not been a good idea.)

I also inspected everything under the playfield, cleaned the relay switches, and installed new bulbs.

After re-installing the boards and plugging everything back together, I turned the game on to see if the bonus scoring problem had gone away. I was dismayed to find that now the score motor runs non-stop, and of course the machine will not start a game and kick up a ball. Looking up, I realized the score reels had not reset, so I manually reset them all to zero. Same problem. Under the playfield, I notice that the #20 Extra Advance relay is clicking and cycling back and forth while the score motor runs and runs. If I physically pull the actuator away from the relay, it allows the score motor to stop. But as soon as I let go, it pulls in again and starts clicking, and the score motor runs. Obviously, something is causing that relay to be energized. On the schematic, it appears that relay is related to switch E-1 on the score motor. I cleaned and adjusted that switch the best I could, but that didn't seem to help. I don't see any problem with the playfield switches that advance the bonus, but I will check them again more closely tomorrow.

I wish I could read and understand schematics better....

On other machines, I have experienced the typical problem where the score motor runs because the score reels have not reset. But I really don't think that is the problem, because they were working just fine, and I had not messed around in the back box at all prior to having this problem. It's pretty clear that I messed up something when I was cleaning switches and tightening the stack screws.

I have the playfield and bottom board back out again, and when I get to the shop I plan to go back through them both and check everything again carefully.

Any other suggestions or advice?

Thanks,
Mike

I managed to fix the problem today. I checked everything again--including everything shown on the schematic MarkG provided above--and found one crazy switch on the score motor that had no gap. So I corrected that. The relays all seemed fine. Got it back together and it started a game normally. The only problem was that the center lane (extra advance) switch was non-functional. After removing and rebuilding the switch (and removing a backer leaf that I believe may have been bridging the switch), that's working fine now too.

Tomorrow evening I'm going to look through the backbox, and try not to go messing around with stuff (since the machine is now working)! Maybe a little gentle cleaning/lubing of the steppers, and that's about it.

I always appreciate the input. Thanks for taking the time to lend a hand.

Mike