I recorded a video of this repair since I thought it might be helpful for some of you guys. I’ve attached the YouTube link of the video at the bottom of the page which goes through a, more or less, step-by-step of the process.
My Tommy has a repro servo board on it, though I still have the old board and think it is OK as well, just the R2 and R5 pots are a little beat up.
Anyway, since the game came with the repro board, that’s what I left in there. It’s cleaner than the old board in layout and has 19 years less use time on it which I’m sure is not a bad thing. I thought the culprit with the blinders not working was the servo motor, and it turns out, I was right on this one.
The old motor would run, but not move the link arm which points to a high likelihood of stripped gears. These little servos are extremely simple and work off of very tiny plastic gears that move in conjunction to swing out the link arm. Over time, and I’m going to go out on a limb and say this one was from the factory, these little gears get worn down and the servo needs to be replaced.
So, I ordered an Airtronics 94102 servo motor to replace the bad one. Several of the pinball parts companies online carry this unit, but have a pretty decent little markup on the price. If you Google “Airtronics 94102” you should be able to find the exact same servo for about half the price from an RC hobby shop.
The most important thing I learned was that the new “Z” connector isn’t as plug-in-play as I originally believed. According to Marco’s, they have an installation note saying the blue wire is the 5v, the red the ground and the black is the signal wire, which would in theory make the servo plug-in-play. However, I found out that that’s not exactly correct after some frustrations with the installation.
The blue wire is actually the signal wire, the red is the 5v and the black is the ground. Their alignment in the “Z” connector will not work with the Tommy servo board, old or repro. So, what you have to do is unpin the red and black wires and switch them so that red will run to the 5v, black with be ground in the center and your blue wire will take the signal feed. There’s a good PDF available online I found which helps explain the difference between the old Airtronics 94102 and new “Z” connector style that has replaced it here: http://jacobwatson.com/images/dads%20images/connectors.pdf.
Other than that, everything was pretty straight forward and just took some careful adjustments. I’m happy to report that I now have working blinders on my Tommy!
As strange as it sounds, I think I need to get a cheaper camera to document some of these repairs. Using what I normally use for some of my freelance gigs, though the picture quality is nice, the no auto focus ability and super shallow depth of field was a bit difficult to work with while trying to do a “how to” by myself. So, apologies on any part of the video that maybe snuck out of focus here or there. Anyway, here’s the video that documents this repair a bit more extensively:
Just as a note, before I put the apron on, I ran the little servo wiring up through the playfield hole to make it a little tidier before putting everything back together.