Here you will find more than you probably ever wanted to know about one type of stepper unit, a Bally 00-90 Match Unit as found in a Bon Voyage pinball machine.
DISCLAIMER There isn’t anything really new as these stepping units or steppers as they are often called have been covered before fairly extensively. In particular Clay’s guides provide really solid information about how they work and how to repair them.
Even with the great information from Clay and other sources, I still felt a lack of understanding as to exactly how these things work, and also a bit of fear of working on them. When I looked at them I saw a complicated-looking contrivance with a bunch of levers and springs and gears with teeth. What if I got it apart and couldn’t get it back together so it would still work right? What if I put something on backwards and messed the whole thing up? What if I killed the function of the whole machine by messing with it? Even though the guides are detailed and excellent, there are still differences between the different stepper units, so you don’t get the specific details on one individual unit you have until you actually work on it.
Since I have 2 Bally EMs with a variety of these stepper units, some of which are definitely sluggish and some not even working 100% right, I knew I had to bite the bullet and just go after it and get it done. But I had to do it in my OCD fashion, figuring out every little piece as I went along. And that’s how you get what you have here. I found that once I got in there, took it all apart, figured out how it works, and cleaned everything up I was able top then easily reassemble it and get it to optimal working condition.
I hope to add some additional details and documentation about this specific stepper unit that others find useful. If you have a Bally EM with this style of 00-90 unit then most of this should directly apply as it appears they used very similar variations of these steppers in a lot of machines (from looking at the parts catalogs). I am not sure how much will apply to other brands as so far I only have Bally machines. But if anything this should provide some useful background information about how these work and how they are put together.
As always any comments, corrections, or criticisms are always appreciated.