Hi All,

I just recently purchased a 1971 Gottlieb 4 Square machine. To set the stage, I am a complete noobie with EM machines but do have some aptitude for basic electronics. Now that I have had the machine a few weeks, I'm starting to piece together how it is supposed to operate and have run across a few issues.

1. The 10 point and 100 point bumpers do not alternate lights. It generally sticks with the 10 point bumpers lit.
2. The 100 point bumper light does not work consistently if it does switch, and flickers when it does.
3. The game does not regularly advance scoring stages (by getting 1-4)

After running across the below Pinside post, I got a lesson in the alternating relay and the 0-9 matching unit in the head. After some inspection it is my suspicion that I probably have a malfunctioning and dirty 0-9 unit, but I'd like to get a second opinion and recommendations on the best next steps.

This video demonstrates the issue:

Pinside post that led me down this troubleshooting path:
https://pinside.com/pinball/forum/topic/gottlieb-4-square-pop-bumper-question

Thanks!
Jake

Thank you for the welcome and reply! If I manually push the plunger, it does advance. I've taken a new video showing the current state and some of the other behavior:

-Jake

Thanks!

I cleaned the sleeve and plunger (not very dirty at all) and found there was slight resistance in the plunger/sleeve relationship. I added a drop of Teflon oil and now the plunger moves as expected and the wheel advances. I took the top of the top wheel off the 0-9 unit and cleaned the contacts, but I'm still having an issue with the light on the 100 point pop bumper either not coming on, or flickering when it does. Since it kinda works sometimes, I'm assuming a dirty contact somewhere. Just need to figure out where it is.

Thank you for the response and recommendation on the clinic, I'll look into that. The disk is cranked over, that is the position I received it in. I believe the wipers are all lined up, but will double check that as well. Over time they have created a groove in the bottom disk and pads, so they all follow the track so to speak.

I am interested in the no lubricant issue. The sleeve and plunger are both metal, are these intended to run dry?

Just wanted to come back to close out this thread and detail the outcome.

I cleaned/polished the sleeve and plunger again to remove any lubricant, and as of now, the 0-9 unit is working like a champ. All game features are working as they should.

The flickering pop bumper light turned out to be completely unrelated. I looked everywhere and then finally realized the ground side of the lamp socked had a really poor solder job from a previous repair. The lamp socket had also lost its spring tension, so the bulb wasn't at tight as it should be. I removed the pop bumper and soldered some new wire on, adjusted the lamp socket, and now it works like a champ. The lesson learned was to start with the easy stuff first.

Thanks again to everyone that replied and helped me get on the right track.

-Jake