I've seen various wiring schemes for JAMMA, some of which use all 8 pins for grounding the board, some of which use 27/e for controller ground, and some which use 27/e and 28/f for grounding the controllers and switches. What exactly is the right way to wire up the grounds? What pins does a board expect to be grounded? Thanks
It's best to use every Ground on the JAMMA connector with decent wire, if you don't then you can get ground problems which can make some games not work properly from crashes, broken graphics or just failing to work. The board generally expects all of the grounds to be connected. Also if you do buy a non JAMMA board then it's possible that the loom will not be wired fully and may fail to work.
In my experience the grounds near the power side are all you require for most boards but there is no reason not to connect the opposite side if you can do so. My JAMMA loom only connects the one near power (+5v,+12v, etc).I've run CPS1,CPS2, and Single Slot MVS with it. Anyway, if you have the option and are worried, wire all the grounds.
