Note: This repair was initially published on Sept. 19, 2011. I republished it with updated photos and information.
I received a call for a Comet with non-working displays. I was told that there were no blown fuses, but the displays just stopped working. No blown fuses indicates a problem with the power supply. I was hoping this was the case as troubleshooting alphanumeric display problems is not a lot of fun in my book.
I was working on a Data East 520-5002-03 sound board that had no output to the cabinet speaker. The cabinet speaker was blown, but there was still no sound output when using a known good speaker. I now suspected that the MB3730A amplifier on the sound board had blown out. When it goes out, it can take the speaker with it.
The Machine: Bride of Pinbot is a pretty neat early WPC title from Williams. It was the last alphanumeric machine produced by Williams. This one was overall in nice shape and had a lot of potential. The main problem was dirt and the typical cracked ramps.
Pinball machines have batteries. A lot of people don’t know this. The batteries maintain your settings and high scores in the game’s RAM. These batteries must be periodically changed so that they don’t leak. Here’s the consequences of not changing those batteries:
