I decided before I started this project to make this cabinet a multipurpose system. With that in mind, I didn't want to hard wire any of the controls nor did I want to destroy any of the cabinet's existing wiring. Since this was a JAMMA cabinet, I wanted to take advantage of that.
Since I had decided NOT to remove the Killer Instinct functionality from the game, it seemed best to make a versatile adapter to attach to the JAMMA connector. I purchased a JAMMA fingerboard from Swallow Amusements in the UK. Steve makes a quality board that is very reasonably priced and a snap to use. It's well labeled and has multiple solder pads for each position.
Since the audio portion was already wired using a quick disconnect into the subwoofer system, the only things I needed from the JAMMA connector were video and the P1/P2 controls. A custom cable was made that went from the JAMMA board to three connectors - 1 video and 2 player connectors. I decided to run not only a ground connection to the video connector but also +5 volts. This came in very handy later.
Below you can see the gray cable from the JAMMA connector to the Dreamcast control box.