I know this is a very old thread, but I just wanted to comment on what this connector is. This is the control connector for the G.I. relay. It's in early Black Knights, with System 6 power supplies. There should be a connector on the relay, that is behind the guys pinky finger. The G.I. will work without being connected, but you won't get the Flashing of the whole G.I. when the Black Knight goes into multiball mode. Sometimes these are disabled because the the Q35 transistor is blown, or the diode on the relay is bad. Which in turn causes the solenoid (F2) fuse to blow. The machine still works without this connection, you just don't get the full light visuals.