I am a repair virgin, who received this pin last summer.
Many problems fixed and a few times, some "fixes" produced other problems.
Can say that I am getting very close to wrapping this thing up and having a very nice, worthy pin.

Background: I have removed cabinet board and PF more than once each to tune up bonus steppers, burnish all switch contacts, and make small adjs to switches. Also, addressed all Jones plugs. In the back box, Player 1 & 2 score reels (3 & 4 appear very clean), and all relays, have all been removed, cleaned and contacts burnished, and all Jones plugs addressed. I have original schematic and it's Instruction Manual too, which is helpful.

Problem 1
Left bonus saucer seems fine: 1) drop, 2)collect down to zero, eject, cool...
Now comes the Right bonus saucer: Saucer allows bonus to step down properly, collecting points as the bonus lamps descend, then a pause at zero, and then it begins collecting the bonus from the
Left bonus stepper to zero. Every time!

I have corrected problems on each stepper, such as, the clock spring being to tight, disallowing the small lever catch to stop the ratchet down at each step (rather, it would spin rapidly to zero position, giving one bonus count for any value up to max. Ugh! But I can't figure out how it allows both L & R bonuses to collect via the right bonus saucer and not the left one!

Side Question: When contacted, should the left and right bumper switches on either side of the Top Hole be alternating which L or R bonus advance insert is lit??

Thanks for any help,
jediKeith

Wow, I did find the right bonus stepper's NC switch had been forced closed by the fiber disc that actuated it, after I re-installed the ratchet gear after cleaning. I will re-assemble and test total function soon and let you know. Thank you!

"Bumper switches"... After plunging (or shooting) the ball (back) to PF apex, it may land in the top hole for 5000pts plus a 2-3 advance of either the left or right bonus. Behind the angled rubber rings on the left and right sides of the top hole are switches that do score when closed, but the left or right advance indicators do not alternate. It seems that they should alternate, as the ball bounces back-and-forth on its arcing descent from the apex. At start of play with each ball, I have noticed that these upper left or right bonus advance indicators do not always coincide with with the lit red arrows for which bonus is collected at out hole. Before each ball plunge, if advance and red arrow matched every time, I would have concluded that the advance bonus did not alternate, independent of the red arrow. On other pins, such as Night Rider, the top hole's point value is alternated by the spinner cycle, or like CaptFantastic's switches alternate features for center vs L/R lanes with each carom. Does this make sense?

Stepper(s) update:
Yes, the impinged switch was the culprit. Once released, collected bonus via both sides stopped. Problem solved, thanks.
Left bonus stepper was not doing the +1 step up after being zeroed. Manual said to visit the 2A or 3A contact on SCRMTR. Burnished up, and that problem cleared.

Newer problems: 1) Landing in right bonus saucer, the payout is always 5,000 more than it should be, as if landing in the saucer is valued at 5,000, or that there is a slight delay after the bonus is collected and another 5,000 is thrown in. Yikes!
2) Before I burnished the 2A(or 3A) contacts, the left bonus was scoring 50,000 regardless of value shown on the PF inserts. Maybe that problem cleared up since the +1 bonus after zero issue was addressed.

Back to top hole "bumper switches"... What are they called? They do score 10pt with each carom.
The Left or Right Bonus Advance do not alternate, whether the ball count changes or if any switches open or close. Top hole indicator is stuck on Right Bonus Advance, no matter what happens through the course of a game, independent of number of players. Ugh!

Thanks for your help.

Oh boy...found that the Change Relay was stuck ON. Wiggling wires to Match Unit switch cycled the Change Relay. Hmm, cold solder joint?
Next, I went to 10Pt Relay and manually closed it repeatedly, energizing the match unit solenoid. The drum in Match Unit is not rotating! Need to take it out and diagnose why no rotation there. That will solve the problem with Change Relay not firing.
More later. Haven't looked at zero position issue on right bonus stepper yet...

Woohoo! Match Unit solenoid removed, pawl placed back on top of drum ratchet and, Kerpow!, the match unit rotates properly, pulsing the Change Relay, which alternates the L&R Bonus Advance lights!!

Zero position issue...
Checked both bonus steppers. No bridging of rivets on either, and both zero well. Manual says the left bonus stepper is pulsed via SCRMTR 2A, and right one via 3A. I have burnished both of those contacts a bunch and made sure they contacted well on each fall on the cam. I have also made sure the tabs on the SCRMTR leafs for those two switches were not broken. So, the +1 bonus advance after zero does not occur on the left stepper, but it does on the right stepper. Now I will investigate the wire runs between the SCRMTR 2A contacts and their closest connection points. Sound like a plan? Please let me know your thoughts, I appreciate them.

Also, the right bonus saucer still gives an extra 5Kpts, with each payout, as if it pays before recognizing any bonus accumulation sting. That being said, know that the bonus collect aspect is OK, because when the left 5k is unlit (left bonus stepper at zero, no +1), it feaks out and jacks the eject coil an extra time. Please think about this and let me know, yo.

Problem solved! Grand Prix is working 100% now!
I tried to short contacts on SCRMTR 2A to see if it would advance the left bonus to 5,000. Did nothing. So I went back up to the left stepper. Someone must have let the playfield rest on the front edge, where the lockdown bar goes, because the left stepper's #14 and #15 solder tabs had been forced together in a near-shorted position. Once separated, the +1 advance from zero worked perfectly and the added 5k score on right saucer stopped too.
Chrisbee, thank you so much for all your insight and direction, it means a great deal to me have conquered the gremlins and have this worthy machine back up and running!
Rural Cinema looks sweet as, dude. Good gig!

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