Jpac / Jamma+ cabinet (Mortal Kombat)

[gsoul]

Okay, I've got a few questions regarding hooking up a J-Pac to a Jamma+ Mortal Kombat machine.

My machine has Mortal Kombat 1,2,3 & 4 in it. Awesome, but I still want to play some classic arcade goodness.

So I hook the J-pac into the jamma harness. The two sticks work along with the button 1 and the 1UP and 2UP buttons, as does the coin door. The remaining 5 on each side do not work.

So what I'm not sure on is the whole grounding thing etc.

So I figure that I add a wiring harness and solder it onto the existing wires (not the black ground) on the buttons, then wire the other end directly into the J-pac. What I'm unsure of is how to ground these buttons. They're already ground to the power supply in the cabinet, but I figure they need to be grounded to the J-pac.

I'm a complete n00b with electronics, so any light you guys/gals could shed would be appreciated.

Basically I dont want to intefere with the running of my super mk cabinet, so I remove the J-pac, plug in the UMK3 board and I'm off.

Somewhere in hooking this up before, I blew the chip on the j-pac, thanks heaps to Andy for sending me a new chip.

So now I figure I need some professional advice.

Ideas?

[gsoul]

C'mon, don't you guys know what I'm talking about? Am I on drugs? Whats going on here?

Someone help me out please!

[markrvp]

I do not have a J-pac, but from looking at the picture below, you should connect the button ground loop to the screw terminal marked:

[gsoul]

So the buttons arent already grounded to the power supply of the arcade machine?

[markrvp]

Don't you have a separate power supply for the computer connected to the Jpac?

In either case, I would try grounding buttons 4-8 for both players to the GND on the Jpac and see if that works.