This two-transistor circuit is from a December 1964 Radio Electronics. Modern transistors can be tested. The headphone must be high impedance or crystal with a 2k2 resistor in parallel.
This power converter or inverter was found in a 1980s documentation. Transistors should be fitted...
This circuit consists of a voltage regulator for 6 V batteries with a very low voltage drop. The...
I found this circuit in an English magazine from July 1982. The circuit is still viable by using...