I guess you wanted 3x108V (324V) instead of 3x85V (255V).
HP often used the 5651A 85.5V reference tube for the voltage regulation with either a valve or transistor based series regulator.
The 5651A has a lower current rating than the 0A or 0G series voltage reference tubes.
Not sure about the 115V one, the last faulty VR tube I found had a crack from one of the pins, I'm sure it lit up at first but I didn't check the voltage until until another fault occurred, the neon must have slowly escaped or mixed with air as the instrument warmed up.
David