Here we go...Grand Prix!

By uncle_jose

1 year ago


  • 15 posts
  • 6 Pinsiders participating
  • Latest reply 1 year ago by John_I
  • Topic is favorited by 1 Pinsider


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0Grand-Prix-Work-12 (resized).jpg
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#1 1 year ago

Hello guys!

Well, this is sad... I (used to) have a perfectly working Grand Prix and while replacing some bulbs under the play field, the play field fell into my head breaking the 500-point tiny coil (M-29 / 1000) on the right side of the play field, tonight I replaced it and now the machine is (still) mad... very mad, so let me start with the first error.

At start up. I will turn on the machine, everything will be nicely silent but when I press the start button, this happens (video):

» YouTube video

The hundred-point score wheel of player 1 will go on and on.. and on.

Any leads on what to look?

Thanks guys!

#2 1 year ago

Something else had to be bent or broken when the playfield came down. Search everywhere possible for broken wires or bent terminals. Also, check and recheck your work on the coil you replaced.

#3 1 year ago

Hey Uncle Jose, Hope your head is alright.

For some reason, the vid won't play for me, but it sounds like you're saying that on reset, the 100-pt score reel is constantly being pulsed and will not stop, even at the zero position? I also assume you meant an M-29 1100 coil (as that is what the documentation specifies)?

As John said, it is possible that something else got broken or disfigured when the PF fell. However, I would first closely check all 3 switches of the 500-pt relay. They should all be normally open (NO), and the tab ends, where the wires are soldered, must not be touching. The topmost switch in the stack starts the score motor, the middle switch is in series to pulse the 100-pt relay, and the lowermost switch is part of a hold circuit to keep the 500-pt relay energized until the motor has run long enough to score 500 pts.

It is possible that one or more of these switches is closed (or the tab ends are touching) causing the 500-pt relay to stay energized and keep pulsing the 100-pt relay.

Let us know what you find.

It looks like you are located just up the road from me. I like your collection.


#4 1 year ago

Thanks for your replies! Yes it seems that something is still bent... somewhere. I'll double check every switch under the play field. One interesting thing though, If I drop down one (or any) of the stand up targets and then power the machine on the targets will go up constantly, meaning that their (4) coils will be firing... rhythmically.

Lee, yes... neighbor! We should get together one of these days!

Thanks again!


#5 1 year ago

Jose, It really seems like some switch that should be NO is closed or shorted and is holding up the completion of the boot up process. For a start, would be logical to check out the 500-pt relay switches closely, or any other relay that might have impacted on you. Let us know what you find.

I'd like to check out your collection someday. Love the early Williams SS games and also the Gott & Bally EMs.


#6 1 year ago

Hi jose +
I join the club and also say: Most-likely some stuff mounted on the playfield.
MAYBE there is MORE than just one thing damaged (?). I like Williams pins, the schematics and the manuals. Here I show a snippet from ipdb-schematics "WHAT makes the Score-Motor turn", "encircled blue": mounted on the Mech.-Panel in the Cabinet, "encircled red": mounted on Insert-Playfield. Look here on page-12 (ori-10) - every relay is listed. And starting at page-25 (ori-23) we see the relays and the switches on the relays.

A good catch: Drop-Down-Targets resetting --- "Switch on Target-Relay" ? / "Switch on Outhole-Relay" ?
Again: MAYBE there is MORE than just one thing damaged (?), greetings Rolf

0Grand-Prix-Work-11 (resized).jpg

#7 1 year ago

Thanks to all! I will check it out with more light and more patience.

Thanks rofl... as always, so accurate!



#8 1 year ago

Ok.. so I'm next to the machine; I went through the switches on the play field and couldn't find anything out of place, so let me describe what is doing right now...

- I will turn on the machine with plenty of credits available
- Press the start button once
- Score wheels will reset Player 1 lit, ball 1 lit.


Sometimes the machine will start scoring on increments of 100 until I turn it off.

Sometimes (and very few times) the machine will be ready to play (silent), but as soon I manually trigger the top out hole, the coil will be firing until I turn off the machine, the same if I manually drop one of the drop targets, their coils will begin firing non stop until I turn off the machine.

Lastly, while the chimes and coils are firing i will press the start button once, player 2 will lit, then it will lit player 3 and ultimately player 4 by itself.

It seems that whatever coil is being triggered (out hole, drop target, or adding a player) it won't stop.

Man, I -really- love these machines but sometimes I rather hug my crazy dog.

Any idea?

As usual, many thanks for your input!


#9 1 year ago

Hi jose
great - I see an Aztec in Your collection - I hope: 100% running. Here I see: The Inlanes around the slingshots are worth 5000 points.
When troubleshooting I sometimes try to put "THE fault" into an 100% running pin - to get hints for troubleshooting in the "pin with THE fault".
Put some points on the Score-Drums on Aztec - lift the playfield and remove the back-door on the backbox --- YOU can look into the cabinet, the backbox and at "underneathside of playfield". Let a friend press the credit-button to start a new game - Your friend (immediately after pressing the credit-button) - Your friend does MANUALLY close forever - always close the Switch on the inlane.
My prediction is: The pin does reset as usual - after the ball is kicked over to the shooter-alley: AAA) the Score-Motor runs and runs and runs, BBB) the "5000 Relay" STEADY pulls (pulls, pulls, pulls ...), CCC) the 1000-point-relay actuates rhythmically and DDD) the Score-Drum is stepped - also rhythmically. Do You see all this (AAA and BBB and CCC and DDD) ?

And now You go to the Grand Prix --- as the "fault with endlessly 100 points" starts happening: Do You see the AAA, BBB, CCC, DDD ? It is hard to see on pictures in ipdb - question: Does the Grand prix has some targets on the playfield WORTH 500 points ? The switch on the playfield bent - faulty always contact ?
I am INTERESTED to read about "500 point relay pulling STEADY (?)" ? and interested about: DOES the 100-Point-Relay rhythmically actuate ? Greetings Rolf

#10 1 year ago

I have a Grand Prix, but no schematic. Your 500 point relay seems to be remaining
energized, or at least in the energized position. The 500 point relay is actually
under the playfield, not on the bottom board. It's the relay right next to
the right inlane's bulb that states "Extra Ball When Lit"
Not sure if you had, but I'd check the contacts in that relay. Maybe they got
bumped pretty close together, and any vibration makes it energize itself.
There's 3 sets of contacts in the 500 point relay. The lower set is primarily
the one you want to make sure aren't too close together..
I believe there's only 2 playfield switches that activate the 500 point relay.
One on the left saying "Advance Left Bonus 500", and one on the right saying
"Advance Right Bonus 500". It sounds like you have other coils staying fired,
but going by your video, I'd recheck the 500 point relay and the two 500 point
switches (and their solder lugs) on the playfield.. (T)

1 week later
#11 1 year ago

Hey guys, I've been helping Uncle_Jose troubleshoot this to no victory yet.... To update this on where we are at. The score motor continuously runs on once you start a game because indeed the 500 point relay is locking on as soon as you start a game. If I take screwdriver in the coil for the 500 point relay and spread it open, it stops running and the game begins functioning as intended, so I know its in that circuit. Checked spacing with the game powered down on the 3 switches attached to that relay, and they are clearly opening, so I don't see it as a vibration issue. I've checked that 2 switches that are labeled as "500 points" and they don't make contact. I figured it was going to be a bent lug touching, but the lugs are good on the switches. I'm guessing something on the 500 point circuit is still triggering. I don't fully understand how what would release the relay once its pulled in, (I.E. something triggers 5 times to add to the "100" point reel, then the 500 relay would power off). I'm thinking it's in that section, but I don't have a clue how that works or where to look.

#12 1 year ago

Hi PinWiz, Uncle_Jose
there is a wire-R-BR-Red-Brown that runs from "Bottom-Switch on 500-Relay mounted on the playfield - runs to a Jones-Plug and then in the cabinet to the Score-Motor. Look here on page-14 (ori-12) - it has text: "Target Relay". Look at this Jones Plug / wire-Red-Brown --- all good ?

I show a snippet of the schematics - put together some stuff / squeezed it. The Score-Motor-SCM-5B does CUT "Self-Hold-Circuitry of Outhole-Relay" and "of 500-Relay" and of many more relays.

See outmost right in my JPG: "my brown" lines --- a short wire runs from "Coil on the 500-RELAY" to (Bottom) Switch mounted on the relay. AT THE SAME Blade / Solder-Lug is another wire (maybe two wires) soldered-on - wire-color-Brown-Black. LET THE wire coming from the Coil AS IS - BUT unsolder or cut the other wire-Brown-Black. Doing so You have taken away the playfield switches (for gaining 500 points) --- question: Does the 500-Relay still faulty endlessly pull ?
And on the OTHER switchblade / Solder-Lug of the switch is soldered-on the wire-R-BR-Red-Brown. Greetings Rolf

0Grand-Prix-Work-12 (resized).jpg

#13 1 year ago

A brief update, Grand Prix is out of the pits! woohoo!

Thank you very much to all for their helpful input! Yesterday Runbikeskilee stopped by to personally take a look at my issue and in less than 5 minutes he pointed out a 500-point switch contact that was stuck together (above the play field, behind a rubber and under a plastic cover!)


Seriously, thanks to all and now I'll be working my way onto Wild Dave's pin. (Card Whiz, my other thread)


#14 1 year ago

Just a point of amplification, we found the issue by examining the schematic and focusing on the only circuits that could have been energizing the 500-pt relay. Apparently, when the PF fell, the right side (where the 500-pt relay is located) impacted Jose's head, but the left side must have bounced off the siderail after the initial impact. We found that the 90-deg angle bracket which mounts the left-side tandem standup switch cluster to the bottom of the PF had been distorted to about an 80-deg angle and the blades on the tandem switch were bent back and making contact with each other just above the PF surface, but under the plastic which made it very difficult to see them. We had to unscrew the switch assembly to drop it down and straighten all the leaf blades with a needle nose.

We also found and fixed another issue impeding the advance of the ball count unit, so it was a productive session. Nice to meet another Pinsider so closeby (~ 15 min drive).


#15 1 year ago

I always love a tech thread with a happy ending...

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