(Topic ID: 204073)

Tech: GTB Sky Jump ball count unit (stepper) teardown & rebuild

By spinal

6 years ago


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  • 69 posts
  • 11 Pinsiders participating
  • Latest reply 85 days ago by zebpin61
  • Topic is favorited by 7 Pinsiders

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Sky Jump Ball Count Stepper 2023.12.31 (resized).jpg
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There are 69 posts in this topic. You are on page 2 of 2.
#51 6 years ago

Whilst slightly overkill, this thing is going to end up better than new. No grease to go hard and gum things up for a start.

#52 6 years ago

Thanks ajfclark - yeah overkill but I learned a lot along the way.

Reset coil is next - new 5064 sleeve of course

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Stop looks OK
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Hold bracket tight to remove all slop before tightening screws - reset coil done.
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#53 6 years ago

Step up coil. New sleeve and plunger sanded with 600 grit then polished silky smooth with mothers aluminum mag polish.

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#54 6 years ago

Bushing
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Other side
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#55 6 years ago

I take my hat off to you for all this work and effort. Sure, maybe not entirely necessary but it is a good way to learn how something works.

As an aside, doesn't this show just how beautifully made Gottlieb machines were? The sheer engineering and quality of the parts give testament to why these things are still very much alive and kicking, many moons on. I wonder how much a like for like machine would cost today?

Back to your post, sorry..

#56 6 years ago

After getting bit by the pinball bug, which was initially based on nostalgia and how much fun they were to play, I soon realized that I'm going to have to learn how to repair these damn things. No one else is going to do it for me and even if I found someone, paying someone could quickly add up to more than what I payed for the machine itself. With EMs especially, I learned that even if one single switch is off by a hair it can render the entire machine unplayable so it was me that was going to have to do it.

Then at some point I found that learning how they worked and the satisfaction that came from fixing them myself were even more aspects of this hobby I could enjoy.

When the insides were still all a complete mystery, drop targets were fun to hit. But now since I've rebuilt a couple of them, it just feels a bit better somehow to hit them. Not just the satisfaction that I fixed them but something more - it's like I can see a bit inside the machine now as they drop - see the springs pulling them down as the ball pushes them over the ledge. Something about this larger sense of awareness of the world around me is satisfying.

Another aspect is the growing appreciation (as you mentioned) of just how beautiful all this hardware is - the dance and interplay of the mechanical and the electrical. At some point humans had to think hard and come up with all these ideas, machine them into metal, test and keep doing this until it worked. Then improve these designs over decades of operation, learning from what parts failed etc.

Anyway, there are many more aspects of this hobby to enjoy than I at first realized - and still a lot to learn! Cheers and thanks for your post @classicpinballs.

#57 6 years ago
Quoted from spinal:

Then at some point I found that learning how they worked and the satisfaction that came from fixing them myself were even more aspects of this hobby I could enjoy.

+1 exactly!

#59 6 years ago

excellent job - thanks for posting so much detail. There is a lot of satisfaction in cleaning, repairing and tweaking the mechanics to the point where they work like a champ.

#60 6 years ago

Next, sanded gear shaft with 600 grit and then polished with mothers mag (before and after).

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#61 6 years ago

Reset spring installed. I had heard 4 winds was standard so that's what I (initially) did. Later I changed this to 3 winds (advice from Steve) since my increment arm return spring was having difficulty returning arm. Reason is that this reset spring works *in opposition to* the the spring that returns the increment arm. So lesson here was that there is no exact number of winds for this reset spring - just try what works best.

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#62 6 years ago

Possible more overkill here but decided to solder wrapped wires on back of ball count disc. Did other rivets too. Used a bit of flux first.

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Then secured disc onto assembly. Then lightly coated path that finger wipers travel with Finish Line dry bike lube for extra smooth action.
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Also applied a bit of Finish Line dry bike lube to tips of finger wipers.
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#63 6 years ago

Excellent work, this will be a nice reference.

#64 6 years ago

I incremented the stepper to very end and at this point the finger wiper (shown) should be lined up with last rivet to right. Then I tightened the two set screws which are for course adjustment so doesn't have to be exact. Fine adjustments can be made with three screws on plate.

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#65 6 years ago

Assembly is done and working silky smooth now.

One of many things that can add to resistance of movement are wiper fingers that have been warn flat and therefore don't slide smoothly over rivets. Here you can see how new wiper fingers look on new rivets - round sliding over round allows fingers to raise and lower smoothly with little resistance (especially when coated with ultra thin layer of Finish Line dry bike lube).

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#66 6 years ago

Question: does anyone know where one can buy the black fabric wrap that covers flexible wires seen above? (PBR does not sell)

#67 6 years ago
Quoted from spinal:

Question: does anyone know where one can buy the black fabric wrap that covers flexible wires seen above? (PBR does not sell)

It's just cotton isn't it? Could you use a round shoe lace? Otherwise I'd be looking for spaghetti insulation like this maybe? https://www.tubesandmore.com/products/spaghetti-old-style-white-20-awg

#68 6 years ago

Ah yes, shoelace - never thought of that! Many thanks!

5 years later
#69 85 days ago

@spinal, for all I know you may not even still own Sky Jump - but wanted to thank you for this very detailed ball count stepper thread. I purchased a Sky Jump 12/15/23 and among other issues, had a ball count that ran 1 thru 4 ok but at ball 5 the PF went dead and "game over" lit in the backglass. Using your excellent pictorial notes I was able to fix the faulty "repair" and the root cause.

Someone had soldered a wire bridge between the 5th & 6th pins causing the 5th ball to equate to game over. The root cause ironically was an over adjusted end-of-advance leaf switch (left most on stepper switch cluster) which prevented the stepper from reaching the last station as designed.

Six years later, but still helping others! Thank you!

Sky Jump Ball Count Stepper 2023.12.31 (resized).jpgSky Jump Ball Count Stepper 2023.12.31 (resized).jpg

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