20KVolt Flyback Supply

This device, which produce abot 20KVolt at high current output (about 1mA), was created to drive TV cascades or high vacuum tubes for producing X-ray. Anyway it may used for lots of HV experiments explained in the Things to Do section. The components used are quite easy to find: the flyback transformer can be taken from an old color TV and the mains transformer can be found in any electric shop.

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This device is a simple high-power oscillator that drive a flyback transformer at 24Khz. The power supply is a simple 55+55 V transformer with the two secoundaries in series. Anyway don't remove R1 because it protects Q1 from overloads. It makes it possible to virtually short-circuit the output without the transistor getting too hot. The diode inside Q2 protect this transistor from extra-tension: so, if you aren't able to find the right version of Q2, you must add any fast-switching diode between its emitter and collector. Because the flyback transformer had a lot of terminals you can find the right winding using a simple tester to measure the less resistence, following the strips on the board, or if you are lucky, looking the diagram of the TV you are working on.

Safety Hints
  • Mount any power component ( like R1, R2, Q1, Q2) on a heatsink cooled by a 220V fan (using insulating-kits).

  • Close the circuit, mounted on a wooden board, into a earthed metal box.

  • And obviously don't touch the output terminals...the contact will be painful