Look at terminal J-1 and see if the two middle terminals are bridged. Looks like the Dsub 25 pin cable MAY wire as follows::: X pos signal from pin 1........14 is X gnd. Pin 2 is Y pos.......pin 15 is Y gnd. The pair of X signals going to X axis driver amp and the pair of Y signals going to the other amp for the Y axis. You might want to check me here as I have not had the chance to get a set of these guys. I would bet Spec would know for sure. It doesn't look like a single ended setup. Marconi may have input here as well. They just don't seem to give all the info needed ...I am still looking over the pages..................
You are the only one that can make your dreams come true....and the only one that can stop them...A.M. Dietrich