High Voltage Generator for Flash and Geiger Tubes

Here is a 700 volt power supply for powering a Geiger tube or charging a capacitor in a flash unit. The

circuit uses a 1:1 telephone isolation transformer typically used in modems. The voltage is determined

by the string of devices including the neon bulbs. Select a combination of neon lamps, varistors or

zeners to achieve the desired voltage. Zeners are available at high voltages but neon lamps are probably

easier to obtain. The circuit shows the power supply in a typical Geiger counter circuit. Geiger tubes

draw about 100uA when they pulse but the pulses are very short and relatively far apart so the supply

need only source a few micro-amps to the output capacitor. Geiger tubes are available in a variety of