One of my all-time favorite circuits is the the following DC-to-AC inverter (click diagram to enlarge) based on an old color TV flyback:
In this AC power supply, a push-pull oscillator drives a TV flyback transformer from an old color TV (a flyback without embedded tripler). The well-known hack is that the original primary of the flyback is not used. Instead, new primaries are made by winding two sets of four turns each of insulated #18 wire around the exposed core of the flyback transformer. Feedback for the oscillator is obtained through an additional coil of 4 turns of #24 wire wound around the core:
I’ve described power supplies based on this circuit in:
In our d.i.y. book “Exploring Quantum Physics Through Hands-On Projects” we show many ways in which this power supply can be used to perform advanced physics experiments.
I can’t remember when I saw this hack for the first time, but last night I was going through some old Radio Electronics magazines and found the circuit described in page 78 of the September 1981 issue. However, I believe that I used this circuit earlier than that. Do you know about the original source of this hack?
DANGER! Please note that this is a dangerous device! It produces high voltages which can cause very painful or lethal electrical shocks. In addition, spark discharges can be produced which can ignite flammable materials or volatile atmospheres.