I recently purchased a surplus HP 85B that apparently had been modified to operate at 48V. In fact the warning on the side of the machine states: "CAUTION - THIS UNIT HAS BEEN MODIFIED FOR 48V OPERATION GND=_12V ON RELAYS AND MODEM". The machine has MCI property tags on it. I guess my questions are:
a) has anyone ever run across a similarly modified 85B?
b) does anyone have a power supply wiring diagram for the 85B or a service manual?
c) could the existing power supply have been modified to run on 48V (or ~60V) without replacing the transformer (maybe bridging a phase on the 220V input tap?? - please excuse my ignorance of electronics design if that statement happens to be preposterous)?
d) what could be meant by the second part of the warning "GND=_12V ON RELAYS AND MODEM"?
e) what should the transformer output tap voltages be (it does appear to have two output taps - I guess one for the CRT and one for the other circuitry)?
Any help would be greatly appreciated.