Here is a picture of the pc
The pin is controlled from an old pc, I think its an intel p200 with 32 meg, not much of a pc. It has a video card and sound card, a cd for playing background music and a 2 gig hard drive. I plug a serial cable into it to transfer files from development pc to the pinball pc. A mess of wires but it works. Notice the PC power supply. The pc power is isolated from the main transformer that feeds all the pinball functions.
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