A push-pull high voltage oscillator power supply circuit includes a parallel resonant LC circuit made up of a capacitor in parallel with the primary of an output transformer. The output power level of the oscillator is controlled or adjusted by gating a drive circuit of the oscillator in accordance with an appropriate timing scheme so as to control the power delivered to the load over a long time period. The drive circuit is switched on and off so as to control the transformer primary voltage by omitting a number of drive pulses, determined by the desired output pulse level, so that the oscillator self-oscillates and rings out with a decreasing amplitude of the self-oscillations, but never reaches a complete cut-off of the oscillations before the drive circuit is gated on to refresh the supply of energy to the oscillator. A circuit for monitoring the collector voltages of the switching transistors of the oscillator may be provided to inhibit the supply of drive pulses to the switching transistors when the collector voltages exceed a given voltage level. This limits the power dissipation in the switching transistors.