Forceflow and Cheddar are spot on.

And in reality, the "Ground" mods have very little to do with static. It is simply about making sure that each and/or every board has a good common ground connection so that voltage levels on each board share the same exact 0V level. For the other manufacturers, this was accomplished with the mounting screws. Leave them off, and you get the same "gremlins". Gottlieb, didn't use a ground plane as their mounting system. Bad connections in 40 year old electronics plague every manufacturer. Use the information and guidance on the internet and you can pretty much bullet proof any system regardless of brand. The availability of new MPU boards has simply prevented many games from otherwise being junked.

There was another thread linking the new parts. As I recall, they are coming out of china for the AMP style black Jamma housing. Just have to find itm

http://www.arcadeshop.com/i/475/molex-pin-snap-in-crimp.htm