Sega System X Jamma Input

[Lastsix]

So I built a jamma to system x converter to test some afterburner boards on my rig and they work ok but I can't use test mode or get any input for that matter. The test button works in the cab. Probing the filter board directly seems to do nothing.

 

[Lastsix]

Okay so, I found a solution. The controls are disconnected from main power and wont work without feeding 5v and ground separately. Connecting the 5v and gnd on the center 12pin connector seems to work. No pinout guides online seem to mention this.

pic for future reference