My backglass lights have been off for a while now. I did the usual reseating the plugs, fuses, etc. and then just let it be since I have other irons in the fire and the playfield lights are fine. One thing I noticed checking fuses is that the fuse holders in this game are pretty crummy and the tabs seem to break often. I think you might want to pull the plugs and check each pin for continuity. That's my plan when I get back to it.

Contacts on the Game Over and Tilt Relays can cause this....

As mentioned above, it is likely one of these fuses or its holder. Another possible if the fuses, etc. are ok is the Alternator relay make/break.

The 00-90 unit does match feature. There is a radio plug in the back box that has to be "in" for it to work.

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File alt relay switch

Could not be the fuseholders as one controls ALL lights on the playfield and another controls MOST or ALL lights in the backbox. The OP said only the controlled lights were not working on the playfield.

That is a viable option or build up the worn teeth with epoxy putty/JB Weld and file/Dremel the teeth to be like new.

That is if you can't find a replacement. They always come up at the shows with used part vendors. Have you tried Pinball Resource?

Which stepper unit is that? Commonly one tooth is missing to keep the stepper from advancing past its end position.

OK lets try this again. From your picture what you call a "worn tooth" is probably not worn at all. Instead the "worn tooth" was probably made that way originally and somebody assembled the stepper unit wrong.

So I was talking about the tooth at 1 and you were talking about the tooth at 2.

If your stepper uses less than half its rotation maybe you can modify it to use the other side of the plastic ratchet wheel.
It could be useful to find the part number and picture in the catalog
http://www.planetarypinball.com/reference/partsmanuals/BLY_Parts_1976/index.html

Otherwise try the usual suppliers like pbresource.com, marcos, etc.

Then search / post on parts for sale / wanted.
https://pinside.com/pinball/forum/forum/pinball-parts-for-sale
https://pinside.com/pinball/forum/forum/pinball-parts-wanted

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Great Thread!!! This one really helped me work out some annoyances on my Old Chicago. Also, on my first pin, I had a partially melted gear on my 10s counter, I had a heck of a time locating one, so I did something similar...In my case, I needed one with all regular teeth, to spin through it’s full range with no elongated notch...I came up with switching out the one on the replay counter, and switching around the pegs to match...Since the play counter only needs 25 teeth at most...I was able to use the (cleaned up and sanded) melted gear.

I'm resurrecting this thread. I am helping a friend with an Old Chicago that he just acquired. The issue sounds similar: no playfield feature lamps are working. All GI (backbox and playfield) and the "feature" lamps in the backbox work (ball and player number, etc). On the playfield, we can get the Extra Ball lamp to light when an extra ball is earned. No other insert/feature lamps show anything on the playfield. Scoring, bonus, etc all seem to work correctly.

I replaced the fuse holders in the front of the machine (3 of them). The plug by the fuse holders had one pin that was discolored and I direct wired/soldered that to bypass the plug. I have reset the various plugs going to the playfield from the cabinet. As noted in Mr Bally's note - I checked the Game Over relay and tilt relay and it looks like the open/closed is correct (I will need to double check that, but I didn't notice any switches that remained open or closed when the solenoid was engaged.

One thing I noticed was on the score motor in the cabinet - see the picture. It looks like a couple switch stacks are blanks (no wires attached). Then, there are a number of wires that aren't attached to anything. The switch stacks look clean (not hacked - if somebody removed the wires, they did a nice, clean job of desoldering). Anybody with an Old Chicago - can you check your score motor switches and wires to see if it looks like the one in the picture?

He has the schematics - I am not very familiar with EMs. Any further suggestions/ideas? Thank you - Conrad

Update: feature lights are working now - the Game Over Relay contacts needed to be cleaned.

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