Location: Longmont, Colorado.

Symptoms: Neither machine working correctly.  Many solenoids powered-up continuously and getting hot, relays buzzing, etc.

Both of these pinball machines are electro-mechanical (EM) from the early 1950’s; Fighting Irish (1950) and Big Hit (1952).  Given the age of these machines, both are in relatively good condition.  They have been in the owner’s family for decades, but haven’t been used for about 10 years.

I inspected the machines and both had sticky, gummed-up, stepper relays.  The Fighting Irish also had some sticky latching relays. The original lubrication on these parts had become gummy over the past 60 years.  This is a common problem with mechanical parts in older pinball machines and jukeboxes.  There is really no easy way to fix this other than to disassemble, clean, re-lube and re-assemble the parts.  Spraying something like WD-40 into the parts, if it works at all, is only a temporary fix.  Days later it will again be sticky once the WD-40 solvent evaporates.

I usually use denatured alcohol to clean the parts, then depending on the situation, use SAE 20 electrical motor oil for lubrication of shafts and Teflon grease for gears and slides.  (Avoid using white lithium grease, as it separates and dries out quickly.)  This only applies to older jukeboxes and pinball machines.  Solid-state pinball machines require practically no lubrication.

I rebuilt the stepper relays and showed the owner how to do it also.  Between the two of us, we got all of the mechanical parts working freely. We had to adjust the solenoid position on one stepper used in Big Hit because there wasn’t enough travel for the “catch lever” to reliably engage the tooth of the main stepper wheel.

The flippers on Big Hit were also gummed up.  They were removed, cleaned and re-assembled.

We powered-up Big Hit and all electrical items seemed to be working fine.  We powered-up Fighting Irish and it still had some electrical problems that needed to be addressed.

I found that the main connection to the secondary of the transformer had broken off.  I re-soldered it.  That got most things working.  Then after scoring about 70,000 points, the machine’s score motor would start continuously running, racking up points and never stopping.

There aren’t any existing schematics available for either of these machines.  So I just watched various relays and determined which ones were used when the machine got stuck scoring.  I held some relay contacts with my fingers and determined that one was repeatedly engaged when the scoring problem started.  With a tone and probe, I was able to trace the power for that relay to another relay’s contacts, and then back to another relay, and then back to the original relay where I discovered a broken wire to one of the contacts.  I re-soldered the wire and all worked fine after that.  When using a tone and probe, the machine must be powered off (unless you’ve got one that can withstand the AC voltage spikes present in an EM game).

A tone and probe seems to be a good tool for tracing wires in a pinball machine, especially when one doesn’t have a schematic.  It was invaluable on this pinball machine repair.  I’m still learning how to use it effectively on EM pinball machines. Since I don’t have an EM machine of my own, I will have to wait until the next repair call to learn more.

The owner of these machines has a number of minor repair items to take care of, but the bulk of the electro-mechanical problems are fixed.