The your best bet is to find someone with a working med-res and have them get you yoke readings (to determine whether it is low or high impedance). The find a cheap or free 19" TV with a good tube (unbroken) and make sure the yoke impedance matches what you need, then call Alva Amusement with the impedance type, neck width, and pin count, tell them you need it for EGA, connect it to the TV tube and yoke. find a monitor frame to mount it all in. Done....