> Gottlieb System 80 pins (Black Hole, Haunted House, Etc.) suffered from
> bad grounding from the factory. Later in the life of the company, they
> figured out that adding a second ground on one interboard connector
> cable would greatly improve reliability. This is a common fix for the
> older games (adding the lead) but the best method is to ground each
> board back to a common point.
I'll echo Al's point, but it goes further than that. I operate a Haunted
House. With it, there were several separate grounds. If the ground
differential between the CPU and the driver board exceeded .6 volts, the
playfield driver transistors started to conduct, causing lots of fried
coils.
The Williams WPC games were bad in their own way. Insufficient trace
widths on the power driver board's grounds, crappy/cheap Molex connectors,
and cold solder joints during the early production runs made these boards
especially fun to debug.
> The system 1 games that proceeded them
> had other problems, but grounding wasn't one of them for some reason.
Because the custom Rockwell IC based MPUs broke far sooner than any ground
problems would surface. ;-)
-->Neil
----------------------------------------------------------------------------
C. Neil Bradley - KE7IXP - The one eyed man in the land of the blind is not
king. He's a prisoner.
---------------------------------------------------------------------------
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Received on Mon Sep 15 15:23:52 2008
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