Rolf - I noticed this post and am having a similar problem with my Old Chicago. Alternator relay was working fine and then, all of a sudden, I noticed the the top rollover lanes and top thumper bumpers weren't alternating each time a 10-point switch closed. I did what you said, watched the 00-90 unit as someone else closed a 10 point switch. The 00-90 unit rotated flawlessly.

Then I opened up the game and did the same thing, watching the alternator relay. It wouldn't close - stayed stuck open. I put on a rubber glove and manually closed the relay with a piece of cardboard and the thumper bumpers and rollover lane lights alternated.

So the 00-90 unit works and the alternator relay does what it's supposed to do. It just won't energize. Any guess why?

FYI - i cleaned the switches in the relay and they all seem to be gapped properly.

Thanks!

Here's a photo of my alternator relay (it's the one in the center).

Old Chicago Alternator Relay (resized).jpg

Relay to the right of the alternator is labelled "Top Hole," which I believe would be the top kickout hole.

You are correct - the spring is missing, although that relay is functioning properly and kicking out the ball.

That wouldn't affect the alternator relay, would it?

Just checked resistance of alternator coil as you directed. It shows 72 Ohms. Close enough?

Gotcha - I found the Jones plug and the wire from/to the alternator. It's plugged in, but I'm guessing it's not making the connection properly...?

What's the best way to clean the plug (I'm still a newbie)?

Thanks to both HowardR and chas10e! I jumpered the connection as you suggested and it worked - alternator now working as it should. When I removed the jumper wires, I tried it again and it's still working. I'm guessing that by reseating the Jones plug a couple of times, it "cleaned" the connection.

I'm curious: is this a common problem? Jones plug connections losing the connection for no reason (other than the fact the game is 43 years old)?

One postscript I wanted to add to this (for anyone who comes along later with the same problem):

I suspect the Jones Plug wasn't the problem after all, although I would not have found it without HowardR's suggestion to use alligator clip jumper wires (and chas10e's original help). When I attached the alligator clip to the alternator relay switch (to the grey/black wire on the right) I noticed that the screws holding the switch were very loose. Perhaps from the constant vibration that unit takes? So I tightened both of those screws, then connected the alligator clip to the switch, connected the other end to the alternator relay and viola, it worked. And then, when I disconnected the jumper wires, it still worked.

I initially attributed that to the jones plug connection being "cleaned" by reseating it a couple of times. But now I'm thinking it was the screws being loose on that switch which prevented that switch from closing. That seems a better explanation for why it was working one day, and then not working the next. (Better than the jones plug suddenly "loosing connection" for no apparent reason.

Anyway, that for all the help. And hope this helps someone else down the road...

Old Chicago 00-90 Unit (resized).jpg

Two corrections: The screws were loose on the 00-90 cam switch (pictured above), not the alternator relay. I noticed it when I attached the alligator clip to the grey/black wire (aka 98-7).

And I meant to say "Thanks for all the help!"