JAMMA (Japanese Amusement Machine Manufacturers' Association) is a connection standard that allows different game PCBs to plug into the same game harness. This way you can change game PCBs without rewiring your cabinet every time. The connector is a 28 pin dual-row (56 pin total) edge connector. Item # 49-0011-00

Make sure that you have the +5 volts loaded to about 1 amp. If there is no load on the +5 volt output, the other outputs will not regulate properly.