This power supply, found in an Argentine publication from the 1970s, uses a wire potentiometer of 25 W or more at the output to adjust the voltage. Transistor Q1 can be a BD136 and Q2 a TIP42, with a good heat radiator. The transformer has 24 V x 1 A and C1 can be 2 200 uF. Resistor R2 is 2 W dissipation.
