(Topic ID: 265932)

Grand Prix schematic


By shado01

4 months ago



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  • 15 posts
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  • Latest reply 3 months ago by HowardR
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Williams schematic state (resized).jpg

#1 4 months ago

I'm working on a Grand Prix. I have the schematic. I am having a problem with the outhole switch and ball count. The game starts fine and plays fine for a ball or two, then either the ball kicks out but the ball count does not advance or the ball just sits in the outhole. Through experimentation I determined that the bonus unit was not properly resetting and that would result in the ball sitting in the outhole. For some reason I can't find the outhole switch on the schematic. I've found the outhole relay at several locations on the schematic but no switch. I can't trouble shoot how the outhole switch connects to the outhole relay through the bonus unit.

Also, does the schematic represent the game with power on in game over mode or the game started with the ball at the plunger?

#2 4 months ago

Outhole switch is located at C/D 15 on a vertical line.

#3 4 months ago

Here's the circuit through the Outhole switch to the Outhole relay.

Quoted from shado01:

does the schematic represent the game with

The schematic represents the game after reset and the power turned off. Let me know if you'd like to hear how I figured that out.
pasted_image (resized).png

#4 4 months ago
Quoted from shado01:

Also, does the schematic represent the game with power on in game over mode or the game started with the ball at the plunger?

From Williams' "An Introduction to Coin Operated Amusement Games":
Williams schematic state (resized).jpg
available at https://www.funwithpinball.com/resources/parts-catalog-list-page-2 among other places.

/Mark

#5 4 months ago

Cataylox just beat me to it. With the schematic positioned with long dimension horizontal, look straight upward from the top of the motor cam #3 by about 2.25". It acts through the make/break switch on the Alternator relay.

Schemaics typically represent the game state with a game started and ball in the plunger lane and then machine unplugged.

#6 4 months ago

Thanks, I don't feel so bad for missing it. Now to hunt down the problem...

#7 4 months ago

Have you been able to track it down to a particular side? Does the failure occur only after a right or left bonus countdown?

#8 4 months ago

I haven't figured it out yet. It's usually after the bonus counts down on the right side that the ball just sits in the out hole.

#9 4 months ago
Quoted from shado01:

It's usually after the bonus counts down on the right side that the ball just sits in the out hole.

Is it ever on the left bonus?

#10 4 months ago

On my GP, the one bonus unit was not aligned properly and had some play in it... the bakelight (sp?) would move if you grabbed it and gave it a light turn. I realigned it properly and my end of ball problems went away.

#11 4 months ago

The only time the ball just sits in the outhole is after the right side bonus counts down.
On the left side the bonus counts down and the ball gets kicked out but the ball count doesn't always advance.
I will also check bonus units for alignment

#12 4 months ago

Yes, the left bonus unit on most machines are out of alignment because people rest the bake light square on the cabinet sometimes. That is a quick hand adjustment to get the bake light squared again. It can happen on any of the units, but that one is the most common because of its location.

As far as your left unit, it sounds like one of the EOS switches is not activating the end of ball/reset sequence.

When the bonus goes to 0, it hits a switch to reset the bonus to 5K and closes the R Bonus reset circuit. Look at section 15 on your schematics. Check to make sure that switch is working properly. Look for R. Bonus Unit Zero Bk

Since the left is working you could compare them visually.

1 week later
#13 3 months ago

Did this get solved? Was sure it was tied to the bonus unit and appropriate switches being activated when the countdown was finished.

2 weeks later
#14 3 months ago

Appreciate the follow up. The problem did appear to be associated with the bonus units. Unfortunately, while trying to make the appropriate adjustments the game no longer starts correctly. I hit the start button, it takes one credit away and that's it. As soon as I figure out what I did, and get back to where I was, I'll continue the trouble shooting.

#15 3 months ago
Quoted from shado01:

the start button, it takes one credit away and that's it.

Page 4 in the manual has the Reset Cycle. How far is it getting?
https://www.ipdb.org/files/1072/Williams_1976_Grand_Prix_Manual.pdf

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