I could use some advice on this one

Williams Grand Prix is not awarding double bonus on the left side bonus, but does so successfully on the right side. This was in a 1 player game, and I haven't had time yet to try a multiplayer one but I'll do so tomorrow. I'm having a tough time understanding, from the schematic, what would drive that kind of problem. Any advice would be greatly appreciated.

I've looked at the Target and Star 1 relays and ruled those out, but I could be wrong. I ruled them out as they don't seem to have any side-specific functionality and the functionality they should have seems to work. It looks like they implement the double scoring by switching the Star 1 relay out of the 1000 circuit and into the 10,000 circuit. Since everything is multiples of 5,000 they can just pulse that 10,000 circuit to achieve the result. I'm just not seeing where the left and right side do that independently.

Thanks in advance!

Dave

Thanks Dan. I had noticed the Star 1 relay switching the scoring circuits. I'm going to look at the bonus units and their associated relays tonight to see if I can figure out how they connect to the Star 1 relay. That circuit switching also switches between 2 cams on the score motor, so I'm going to take a look there too.

Dave

OK, some add-on info. If I collect the bonus via the left saucer, the bonus is indeed doubled. If I collect it via the outhole, it's not. On the right bonus, it doubles when collected either way.

And talk about feeling stupid. I spent way too much time tonight poring over the schematic trying to determine why the switches to the left and right of the upper saucer were scoring their points but not advancing the bonus when the light near them was lit. Of course, the light refers to which bonus the saucer will increase and has squat to do with the switches DOH! I only noticed this by happenstance while working on the double bonus issue after getting frustrated trying to figure out my non-existent issue!

I apparently have some score motor switch issues, or at least one anyway, as occasionally pushing the start button won't do anything. Physically move the score motor a little and off she'll go. Hopefully just a bad or dirty connection on the Run switch.

Advice still welcome on the bonus doubling issue!

Thanks rufessor - I will take a peek at that tonight. Given that it is just the outhole award that's failing, that path seems very likely.

For completeness sake and for anyone who may search out similar issues in the future, I am happy to report that I have fixed the final 2 major issues with Grand Prix. Multiplayer appears to now be working, though I have only tested two player so far. Previously it would continue up to Player 4 and stick there. It's now playing a 2-player game correctly and I suspect 3 and 4 will be OK also. This turned out to be a broken wire on the Coin Unit. It broke up inside the cloth insulation, so a visual check revealed nothing. I found it while doing a tug test on the wiring after cleaning the unit.

I also managed to track down the very erratic left-side double bonus error. This turned out to be a combination of things. The teeth on the left bonus unit gear are worn. The unit was also very sticky and sluggish. After cleaning, it moved freely but the error was still there. After manually logging each bonus value and what was being scored into a spreadsheet, it was easy to confirm that it was never the same error, but was always on the left side as I suspected. Since nearly everything else in the circuit is shared, I focused on the few side-specific items. The left side relays looked fine but I cleaned and gapped them all anyway, to no effect. I then watched the bonus count process on the stepper unit and you could see it skipping past teeth. A closer look revealed that some of the teeth are fairly worn down. The pawls looked pretty good though so I thought there should be enough tooth there for it to still work. I changed the reset pawl spring but again, no change.

I then had my brainstorm... With the unit having been gummy, it occurred to me that someone may have cranked up the mainspring tension to make the unit work rather than spend the time to disassemble and clean it as I had just done. I popped the end of the mainspring off its stud, and I could feel that it had far too much tension compared to normal steppers. I unwound one winding and tried again. Success! A full bonus countdown with no skipping. The high spring tension had been rotating the gear faster than the reset coil could cycle and this was made worse by the slightly worn teeth.

I'll still try to source a new gear for that unit, but it should be good for a while now.

All in all, a satisfying night's work!