Pascal was right, I took the pcb to my old friend and he told me that there are some "blockers" in the mainboard, that keep the jamma adapter's harmful electricity away from it, so I have to connect both plugs.
It's up and running, a lot of fun games in it, that I didn't want to buy in original pcbs.

Of course it couldn't get close to an original dedicated cabinet, especially a Hyper Olympics with a Hyper Sports "spare pcb"!!!

Am I right Ully?
