Electro Mechanical (EM) Pinball Repair of a Gottlieb Jack in the Box

EM Pinball Score Reel

First of all, yes, I know that my featured image is of a Bally score reel. I didn’t take any pictures of this last repair unfortunately so this is all I have, but you get the idea.

Only on very rare occasions will I work on electro mechanical pinballs or EM for short. I usually only do it as a favor for friends because fixing EM games is a completely different ballgame.

The photo for this post is from a Bally Old Chicago I fixed for a friend of mine last summer. The issue was one of the score reels was hanging up and when that happens the game usually will not start if it cannot return to zero. You will just hear the motor running endlessly trying to find “home”.

This repair of the Jack in the Box was the same issue. The game was acquired for free so my friend didn’t mind putting a few bucks into it. He said it was playing fine for a few days then suddenly wouldn’t start. The motor was running constantly with a bunch of relays clicking and the game wouldn’t do anything else.

As soon as I tried to start a game I noticed the 2nd player hundreds reel was stuck on 1. It didn’t even seem like it was trying to move when the game was resetting. On the few EM games that I’ve worked on in the past the score reels could easily be removed by either taking out a small hair pin clip or in this case a small plastic tab holds them in.

I took the reel out and manually set it back to zero. After that the game started and could be played. There was another issue though with the pop bumpers.

He already had the left pop bumper lock on and melted the coil so he cut the wires to it. On Jack in the Box both pop bumpers fire at the same time, which is sometimes the case on EM games. I really don’t know how both coils didn’t burn up but the right one was fine.

Now because I don’t know when he worked on the game or what else was happening before I got there, I imagine both coils were most likely locking on. When I played a game the right pop bumper would lock on when it was activated.

If you aren’t too familiar with EM games, which I’m not, you really need a schematic, which he fortunately had and it was in great shape. I was able to see that the pop bumpers were controlled by the “B” relay. On Gottlieb’s the relays are usually assigned a letter designation. Then all I had to do was find it in the mess of relays under the playfield. I was able to see that the four switches were opening and closing properly and making good contact.

All functions on EM pinballs are controlled by relays, mechanisms and banks of switches. If any one of those are out of whack the game won’t work, or work properly.

The reason the pop bumper was locking on was because the relay is designed to stay energized until both pop bumpers have fired. After they activate each one opens a normally closed (NC) switch which releases the “B” relay. This switch is similar to a point switch on early Williams solid state games.

Because the left pop bumper wasn’t firing the switch was never opening and is why the right pop bumper was locking on. The switch was pretty mangled up and may not have been opening correctly from the beginning. Because it was already taken apart I have no idea of what was actually causing the problem.

As a temporary fix I just bent the leaves of the switch apart so the right pop bumper could work normally.

This game, like most EM’s I come across, have sat for a very long time months, years and even decades. This is the worst thing you can do to an EM pinball. They need to be played regularly, all players so all score reel are kept moving if they are a multiplayer game.

The majority of the games I see need an extensive overhaul. All switches need to be cleaned and sometimes each of the score reels, ball count and other mechanisms need to be completely taken apart, cleaned, lubricated as required and re-assembled. Only then will they work correctly and be dependable.

On the Old Chicago there was an issue of the game not starting because the ball count mechanism wouldn’t return to ball one. I ended up having to take it apart, clean the grease and gunk out of it and put more tension in the return spring. That’s the main problem I’ve seen with EM pinball machines. Springs lose tension, the little cams, sprockets and leavers get dirty and gummed up and won’t move so things stop working like they should.

I tell people that I’ll look at your game and see what I can do but it will be up to you to take the hours and hours required to clean and rebuild all of those things that are keeping the game from playing. It’s because most games need all of that work that I can’t take them on more regularly.

This is where solid state games are different and troubleshooting is usually much easier. On solid state games if a coil locks on it’s because the drive transistor shorted, most of the time. That can happen for no reason or because the clamping diode shorted. I’ll discuss clamping diodes and why they are used in a future post.

Until next time!

Readers Comments (2)

  1. Curious how you ended the article. Solid state machines coil lock due to no reason?
    How do you solve for that?

    • Usually, a solid-state pinball machine coil will lock on when the drive transistor is shorted, that’s the most common reason. If the transistor is blown, you’ll need to make sure the diode isn’t shorted. Best practice is to replace the diode anyway since it only costs a few cents.

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