This simple circuit is intended to test the zener test. RV1 can be calibrated in terms of voltage. The maximum voltage of the tested zener is that used in the circuit supply.
This power supply, found in an Argentine publication from the 1970s, uses a wire potentiometer of 25 W or more...
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...
The oscillator shown in the figure generates a 1 kHz tone that is reproduced on the speaker with...