Abstract: The improved power supply of the present invention adjusts the voltages applied to an image tube to provide automatic brightness control and automatically compensate for temperature changes. A first oscillator, transformer and multiplier supply DC high voltage to a microchannel plate (MCP) electron multiplier of an image tube. The oscillator is controlled via control circuitry to modify the voltage applied to the MCP to automatically compensate for temperature changes associated with an image tube and to provide an automatic brightness control mode of operation. A second oscillator, transformer and individual multipliers are used to supply appropriate DC voltages to the cathode and screen of an image tube; these voltages are also automatically adjusted for temperature changes associated with the image tube. The screen current is detected and is used by additional control circuitry as feedback for the first oscillator to provide the automatic brightness control mode of operation.