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(Topic ID: 251731)

Reference pic GTB 4-player

By drscottsmith

1 year ago

Topic Stats

  • 12 posts
  • 3 Pinsiders participating
  • Latest reply 1 year ago by drscottsmith
  • Topic is favorited by 1 Pinsider


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There have been 6 images uploaded to this topic. (View topic image gallery).

3e9bf94055eaf92a5b6631a6d0f1f2291b38f7aa (resized).jpeg
College Queens Ball Count 2 (resized).jpg
College Queens Ball Count (resized).jpg
image (resized).jpg
0BBF68CC-A160-49A3-98BE-92F4C598CFAE (resized).jpeg
3A738A4A-05DC-4F5F-9F01-A70ACA6AE16B (resized).jpeg

#1 1 year ago

All -

I need to verify 3 things:
1. armature oriented correctly on this unit.
2. Disc oriented correctly on armature.
3. Wires on disc are in correct locations.

Ball Count unit on a 4-player College Queens (GTB).


0BBF68CC-A160-49A3-98BE-92F4C598CFAE (resized).jpeg3A738A4A-05DC-4F5F-9F01-A70ACA6AE16B (resized).jpeg
2 weeks later
#2 1 year ago


#3 1 year ago

if you don't get a reply, try hitting up nicovolta he can probably answer this in about 20 seconds.

#4 1 year ago

Hard to say without a schematic but maybe we can sort it out anyway.

Does this stepper have just one solenoid? In other words can it only step forward and not step backward or reset? If that's the case it will probably work properly as long as the wipers are centered on the contacts below. Just mount the armature firmly on the shaft, then mount the disk on the armature and use the slotted holes in the disk to align the wipers with any contacts below. Once the disk is secured advance the stepper manually by pushing the plunger all the way into the solenoid and releasing it. The wipers should step cleanly from one set of contacts to the next every time with no hesitation.

Steppers that have two solenoids have a fairly obvious reset position. Steppers with just one solenoid however do not. During reset they need to be able to find the appropriate starting position on their own. Imagine for example if this game were unplugged before game over. The Ball Count unit would be in an arbitrary position. The design would need to be able to find a starting position as part of the reset sequence.

Have you tried just mounting it an aligning it with arbitrary contacts? Does it not work?


#5 1 year ago

Hey Mark -

Yes tried to remount the disc but I have idea which way is correct (obviously it could mount 3 different ways - and even within that would have some variance).

I guess what I need to know is what are the arbitrary rivets? It is a step-up/step-down unit, so two coils, and it has a definite stop counter-clockwise (which I assume is reset).

I do have a schematic - but my eyes, steppers and schematics don’t always work correctly. Below is a pic of the schematic with what I believe would be a good reference, but not sure how the schematic language translates to the wiper disc and the river layout.

I also am not sure the wiring on the top of the disc is correct, but not sure how to check.

Thanks in advance!

image (resized).jpg
#6 1 year ago

Ok, since your stepper resets we'll have to take another approach. The schematic shows the game just after reset (it might even say so). You can use that to help identify where the wiper disk belongs. In the image you posted you can check the highlighted path with your meter:
College Queens Ball Count (resized).jpg
With the wiper in position 0, your meter should measure a resistance of an ohm or less between the white-brown wire on the AA relay coil solder lug and the common wire on the stepper whose color is not shown. That's not conclusive since you'll make that same connection in every 4th position. But elsewhere in the schematic you'll find similar notations with a dashed line around a circuit with the "Ball Count Unit" label that will give you other connections to check to identify where certain positions are.

For example there may be a similar feature near the Game Over light that will tell you what wires need to be connected through the Ball Count Unit in the last position. With a couple of similar clues you should be able to zero in on the correct position for the wiper disk.

#7 1 year ago

Here's another set of clues from your image:
College Queens Ball Count 2 (resized).jpg
The green-black wire connects to:
- orange-red in position 8
- brown-red in position 9
- green-red in position 10
- etc.

Remember to check for an ohm or less, not just continuity.

#8 1 year ago

OK - I think I see where you are going...I will take some addition photos of the schematic as well.

So...was there no common logic from GTB on the numbering of the rivets on any given game? I would have thought that either the one circled in red or blue on the photo below would be that position - but maybe not?

3e9bf94055eaf92a5b6631a6d0f1f2291b38f7aa (resized).jpeg
#9 1 year ago

My problem is that there are a bunch of ‘0’s on the schematic and thus the unit...are the rivets not sequentially numbered all the way around any one arc?

Here is a video of what it does on startup...

#10 1 year ago

The 0s and other numbers used on the schematic in reference to the steppers refer to the stepper position, not the contact. So for example in reply #7 the first number shown represents stepper position 8. There may not be any contacts in that row in positions 0-7. In fact the four contacts shown in that schematic for positions 8-11 may be the group of four contacts in the lower left of your photo, one ring in from the outside ring.

#11 1 year ago

Aha ok now that makes more sense. So the stop point counter clockwise is position 0 (can’t go any further that way - and each advance of the mechanism clockwise is one position (eg 9 clicks to position 8 on schematic).

#12 1 year ago

Got it - thanks all!

Still have to adjust the Vari Targets and I have no feature lights yet, but I can play a complete game and all scoring works.

Thanks again!

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