Going through a Grand Prix for a client, which was a bit of a basket case: stuck score reels, no player count, no ball count, skipping bonuses, etc etc. I've got just about everything sorted out and the game is now playable and fun except for one last bug:
It matters not what you touch: left standup, right standup, left scoop, right scoop, top scoop, left outlane, right outlane, left spinner, right spinner... every trigger will cause BOTH the left and right bonus units to advance, simultaneously.
They do count down (award) independently and score correctly.
Worst part is, I'm fairly certain this was not one of the original problems with the machine, but I'm not 100% on that. At any rate, it's driving me crazy because in the schematic, the ONLY link I can find that could tie both the advance relays (L + R) together, is the make-break switch #A on the Change Relay. The way that relay works and is drawn, it should be possible for only the L *or* the R to fire at any given time.... that is, literally IMPOSSIBLE for them to both fire UNLESS the M/B switch was mangled shorting both sides together. Well I checked that, and it the Change Relay #A M/B is fine. No shorts. Nice gaps. I cleaned it for good measure. Problem persists. I jammed an index card between both sides to defeat it, problem persists... so that seemingly rules out the Change Relay...?!
...which leaves the score motor, as there are a few M/B switches related to the L+R Advance relays there. But as much as I could tell by carefully turning the cams and probing the switches, all seems OK. Now I might have missed something because as you know, it's hard to see and probe every last switch tang in the motor nest and I'm not convinced the problem is there to begin with. But, on the Index cam, switch D (Advance relays) there is an "extra" green wire that's connecting to a switch on Cam 2... this wire isn't on the schematic, but the solder job looks factory so I'm not inclined to suspect it off hand.
I've looked at all the other relays, and everything looks OK with nice gaps and contacts. No shorted wires or tabs where I've thought to look. If I touch the L Adv relay, the R Adv works too and vice versa. Same if I touch the 500 relay. Same if I turn the spinner units. Makes no difference if I turn the number match unit (the lights select alternate sides, but both sides still score).
All other game functions work fine. So what in the world am I missing that would link L+R together?
Also, hopefully simpler: what is the rollover switch in the top arch lane, left side (after the spinner) supposed to do? It's wired in (to GI?!) and does absolutely nothing.