Pacman Arcade Machine Wiring?

I have an old Pacman arcade machine (the yellow one) and i have two lose wires under the control panel. one of them is black (which im sure is the ground and just need to ground it to a screw) and the other one is yellow and black. where does that one connect to?? im thinking it goes to the upper prongs (that makes pacman go down) because i can get pacman to go down. but i dont want to wire it wrong. these wires are pretty old too, so i just might get a whole new wiring harness. but i still need to know where the yellow wire goes.