The power transformers in these units had dual primary windings, and could be done for either 120 or 240V.
Call me with the units at hand and their covers off so we can determine the way they are now wired.
651-330-9871
You MUST use your variac to bring the AC line voltage up very slowly, over a period of hours, a small bit of voltage increase at a time, to avoid destroying the power supply electrolytic capacitors. A "hard" turn on to full line voltage will likely short out and damage these old parts, especially if they have been unused for many years.
Frank Van Alstine