Abstract: A power supply line has two to four lead wires which are selectively connectable with terminals (10a-10d) of a transformerless AC-to-DC converter (A). The lead wire interconnection scheme is selected (FIGS. 1A-1D) in accordance with whether the line signal is single phase or three phase and whether the line voltage is 220 or 440 volts. The AC-to-DC converter produces a 620 volt DC, signal across its outputs (26, 28). A first inverter (B) converts to a pulsed AC signal and applies it across opposite phased primary windings (46a, 46b) of a step up transformer (C). Two pair of alternately phased secondary windings (48a-48d) and rectifier bridges (50, 52) provide a high voltage DC bias across a cathode (54) and an anode (56) of an x-ray tube (D). A summing junction (66) compares a voltage sensed across the x-ray tube with a reference voltage and generates a voltage deviation signal.