Hi,
I can't help you out, but are you sure that the unit doesn't get any digital data signal via the other (not coax) pins? I have a Airbus CRT Display Unit together with a DMC here and there is a digital connection Airbus called DSDL between them.
Don't ask me what DSDL exactly is, I didn't find the time getting my setup working (Plus I don't have a 115V 400Hz AC source, yet). Apart from that the DUs receive a sort of digital component video from the DMC for weather radar display. Maybe your coax connectors have the same purpose?
I have the same problem... Getting information is really hard, CMMs would help, but honestly, I don't know where a private person should get those...
Simon