Tommy Pinball Wizard Repair: Replacing Trough Rollover Switch

I’ve got two repairs I’ll be doing on Tommy this weekend. One is pretty minor, and the other isn’t major, but a little bit more intricate. For the second, I will add a video of my progress in case it is valuable to anyone else with the same problem.

For this fix, however, I will just snap a few pictures and try to walk you guys through the problem and the solution. The other day, I was playing Tommy and some odd things started happening: Jackpots continued in multiball mode even once I was down to one ball, and then when it drained, it didn’t go into the end of ball bonus phase. With a little nudge, the sixth ball was recognized finally, but once the bonus was calculated the next ball shot out two balls rather than one. I knew immediately that I had a trough issue on my hands as all of these signs are classic examples of ball trough issues.


The middle lug broke off the furthermost trough rollover switch.

Sure enough, when I lifted the playfield, I noticed the furthermost trough switch had an problem. At first, it looked as if the double-wired positive green-red line had simply come desoldered from the middle lug; however, upon further inspection, the entire middle lug had come off!


Radioshack conveniently carries a suitable replacement! Part #275-017.

Luckily, Radio Shack carries an equivalent part in stock, so I didn’t have to make an online order with one of the many online pinball parts companies and wait for a few days before tackling this issue. The part at Radio Shack is part #275-017. I picked up two, just to have one more on hand.

As you can see in the picture, the middle lug came completely out. With a small phillips head screwdriver, I took out the two screws holding the trough switch in. After that, I desoldered the blue-white ground wire from the rightmost lug. At this point, just take note of the orientation of the N4001 diode that is soldered between the outer two lugs, and then disregard the old switch/diode.

I could have probably salvaged the old diode, but with as cheap as they are, I just used a new N4001 blocking diode. I soldered it in array on the outermost lugs, same orientation as the rest of the switches, which was banded side towards the leftmost lug if you are looking at it as it is oriented in the machine (side without the white-blue wire). After that, I soldered the white-blue wire onto the right lug (non-banded side) and then soldered the double green-red wire onto the middle lug.


The finished product!
(Insulator tubing pushed up all the way after this photo was taken.)

With the new switch, it might need to be adjusted a bit to fit the screw holes and still register  when the balls are over it. Screw in the two holding screws and make sure the switch is engaged (clicked) when balls are resting on top of it. If you can press the switch and hear a click when the balls are resting over it in the trough, you need to take it out and re-adjust.


All six balls registering properly! One fix down, one to go!

I fired up the game, no “Pinball Missing” error message on the screen. Went into diagnostics just to double check (this can be confusing on DE games sometimes. Push the green push/pull in so it is engaged, do it on both green push buttons if there is a double set of knobs on the coin door, and then press the black button). In diagnostics, as hoped, all six balls were registering. I fired up a game, and everything worked perfectly.

One fix down, and one to go! My other issue is the Tommy blinders weren’t working when I got this machine. The previous owner bought a new board, but I don’t think the board was really the issue on this one, though an update over the 19-year-old original board is definitely not a bad thing! I think the servo motor has stripped gears. I’ll probably be doing that fix tomorrow, so tune in for a video of if my theory is correct as I install a new Airtronics 94102 servo into the blinder mech on Tommy!

About Matthew Mandarano

Matthew is a cinematographer and video specialist by day and pinball fanatic at night. Somewhere in between he also finds time to play the guitar, collect vinyl records and watch a good deal of movies and TV shows.
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1 Response to Tommy Pinball Wizard Repair: Replacing Trough Rollover Switch

  1. Jan Karicher says:

    You have a very impressive web site.

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