Location: Littleton, CO
Symptoms: GI lights not working, battery holder corrosion, tune-up
Only a few upper playfield general illumination (GI) lamps were working. There was no voltage at the lamp sockets, so I looked in the backbox for the problem.
The GI lighting connector was burnt. This is a common problem with many pinball machines. The root cause can be a number of things such as contact oxidation, a shorted lamp circuit, or even poor design forcing too much current through the connector pin. Once the scenario starts, it is self destructive. Any of these root causes will cause the connector to heat up, which in turn causes more oxidation on the metal surfaces, as well as reducing the spring tension on the female contact. All of which cause it to get hotter until it fails.
I replaced both the male and female connector with Molex Trifurcon which have a better current carrying capability than the originals. The female pins contact the male pin on three sides instead of just one or two, giving it some redundancy.
This machine had been in storage for a number of years. The AA batteries that supply power to the RAM to hold the high scores, had leaked and damaged the battery contacts on the holder. Fortunately, this era of WPC boards have the battery holder piggy-backed over the CPU board, so if the battery holders get damaged, the main CPU board doesn’t.
I removed the battery pack completely and also removed the RAM chip. I replaced it with an anyPIN NVRAM module. The batteries are no longer needed. Ever.
After tuning up and replacing a bunch of bulbs, the pinball machine was working great!