(Topic ID: 264880)

Grand Prix Startup Problems


By Black_Knight

12 days ago



Topic Stats

  • 16 posts
  • 6 Pinsiders participating
  • Latest reply 10 days ago by paulace
  • Topic is favorited by 2 Pinsiders

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#1 12 days ago

Working on my next project while stuck at home.

Spent most of the day working through score reel issues from a fire and some previous repairs that didn't look right. I got all the score reels capable of resetting to 0 consistently. (this tells me the 0 switches work on all digits, i think)

However, when I hit the start button, score reels and drops all reset, but the main motor runs constantly along with the bonus units.

If I disengage the reset relay manually, the game works, with most functions appear to operate. I can even add multiple players, and the score changes normally. Note the relay coil is still engaged and hums.

So my question is - what do I need to start tracking down on the reset circuit?

As noted above, I think the score reels are right, since they all stop at 0. What's Next?

TIA.

#2 12 days ago
Quoted from Black_Knight:

what do I need to start tracking down on the reset circuit?

To track it down yourself, see page 4 of the manual
https://www.ipdb.org/files/1072/Williams_1976_Grand_Prix_Manual.pdf

#3 12 days ago

Thx. I should have said I read that already. Just doesn’t make any of sense to me as it is written.

Plan to go through it again in the morning with a clear head.

#4 12 days ago

If the Reset Relay doesn't release on its own, the first step is to find out which of these 24 switches/relays is keeping it energized.

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#5 11 days ago

Thanks Howard.

Looking at it with some coffee today, I will block off the bonus relays and see if that does it. I’m assuming it’s the EOS switch on the unit.

As I mentioned, all the score reels stop at 0 so that tells me the 20 listed there should be good. But if there is a central wire for me to block all of those let me know. I don’t see anything on the player unit.

the letters just outside the first box- M.B. IND-D with a weird symbol. Is this a make/ break from the score motor? How do I read that to determine which one it is? D - 4th one from the motor?

Any reason you left it out of the box?

#6 11 days ago
Quoted from Black_Knight:

Thanks Howard.
Looking at it with some coffee today, I will block off the bonus relays and see if that does it. I’m assuming it’s the EOS switch on the unit.
As I mentioned, all the score reels stop at 0 so that tells me the 20 listed there should be good. But if there is a central wire for me to block all of those let me know. I don’t see anything on the player unit.
the letters just outside the first box- M.B. IND-D with a weird symbol. Is this a make/ break from the score motor? How do I read that to determine which one it is? D - 4th one from the motor?
Any reason you left it out of the box?

That is a Make Break switch on the scoring motor. The switch stack would be the INDEX switch stck, switch position "D".

#7 11 days ago

Thanks, that's what I thought.

The 4th Make Break stack looks like it is operating correctly, and I blocked them both off to test, So I don't think this is the issue.

The EOS is def open on the bonus units when reset to 0. I assume this is what I'm looking for there.

New theory - Went back to the score reels and looks like there are two open switches on the score stack when the reel is at 0. The one I looked at earlier controls the reset circuit for that reel only, I think.

The top switch looks common across the reels and I'm going to check those visually, then block them off if I can't see anything.

#8 11 days ago
Quoted from Black_Knight:

Thanks Howard.
Looking at it with some coffee today, I will block off the bonus relays and see if that does it. I’m assuming it’s the EOS switch on the unit.
As I mentioned, all the score reels stop at 0 so that tells me the 20 listed there should be good. But if there is a central wire for me to block all of those let me know. I don’t see anything on the player unit.
the letters just outside the first box- M.B. IND-D with a weird symbol. Is this a make/ break from the score motor? How do I read that to determine which one it is? D - 4th one from the motor?
Any reason you left it out of the box?

Make sure the bonus unit home switch is making contact and the leafs are on the correct side of the pin. I have seen these get out of adjustment after the wiper contacts are removed for cleaning and the disc is forced past the home position or the opposite and forced past max bonus. The game will not reset when this happens.

#9 11 days ago
Quoted from Black_Knight:

all the score reels stop at 0 so that tells me the 20 listed there should be good.

A separate switch on each score reel controls the Reset relay. Locate by wire colors.

Quoted from Black_Knight:

But if there is a central wire for me to block all of those let me know

There isn't. You have to block each of the 20 separately.

#10 11 days ago

Ended up being the Player 4 100 point reel 0 indicator.

Thanks for all the suggestions. Now I’m off to clean it up.

#11 11 days ago

Hello,
A little kate in the conversation but i thought i could add this for future reference in regards to how the score wheel switches operate. Comes from either a manual or a parts catalog cant remember.
May not be fully relevant to the situation but won't hurt.

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#12 11 days ago

Fred736 - That's always good information! Thanks for the visual.

#13 11 days ago

Thanks for that diagram. Staring at these stacks drives me crazy.

There is actually still something going on with the player 4 reels. Even when the 100 reel operates like the pic, it won’t reset points and it resets forever if it isn’t 0s.

I think it’s in the player unit though as I noticed player 3 got some points added as it moved from p4 to p1.

As long as I play 3 players it works and resets fine.

I checked the ball count unit and fixed the Coin unit which was turned past the ‘EOS’ switch.

It’s not on free play and I had to fix the credit unit which was turned past the end too.

Now I have a left bonus issue. That one should be straight forward.

Basically this machine is a POS, but I got it for a couple hundred bucks and it’s providing a lot of entertainment while I’m stuck at home.

Wish I could move faster on it, but I’m learning a lot.

I really bought it for the BG which is the nicest I’ve seen in a while.

Thanks for all the help, I’ll prob set up a new thread for the player unit/p4 scoring/reset issue.

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#14 11 days ago

I think you have to try to find a way to enjoy the process of troubleshooting EM's...between learning the quirks of how each company writes their schematics, trying to understand the logic behind the design, and trying to translate the symbols on the page to the actual parts, there's alot to take in. Just be patient and try to enjoy it as much as you can. Grand Prix is a great game - Steve Kordek mentions it as one of his 3 favorite games that he designed during his long career. From what I can see, that one looks pretty nice too!

But there IS a boatload of stuff crammed into that game!

#15 11 days ago
Quoted from paulace:

I think you have to try to find a way to enjoy the process of troubleshooting EM's...between learning the quirks of how each company writes their schematics, trying to understand the logic behind the design, and trying to translate the symbols on the page to the actual parts, there's alot to take in. Just be patient and try to enjoy it as much as you can. Grand Prix is a great game - Steve Kordek mentions it as one of his 3 favorite games that he designed during his long career. From what I can see, that one looks pretty nice too!
But there IS a boatload of stuff crammed into that game!

This is my third GP and I’ve fixed a dozen or so em’s over the years, but this one is a bigger POS than any of them.

Burnt coils and wiring, poor/incorrect repairs, every unit is screwed up somehow, even the pf is shit. I have no idea how a machine can get into this state!

I’ll get through it, just hope I have enough beer to last through the process. It’s been great timing with the lock down, but I also have 2 other projects lined up right after this one.

#16 10 days ago

Well, at least you have that nice backglass - good luck!

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