Diode Zener Tester Circuit Diagram
The circuit has main advantage that it works with a voltage as low as 6V DC and consumes less than 8 mA electric current. This diode zener tester can be fitted in a 9V battery box. 1/3 of the box may be used for four 1.5V batteries and the remaining 1/3 is sufficient for accommodating this circuit. In this circuit a commonly available center tap transformer with 230V AC primary to secondary 9-0-9V, 500mA secondary is used in reverse to achieve higher AC voltage across 230V AC terminals. Transistor T1 (BC547) is configured as an oscillator and driver to achive required AC voltage across transformer’s 230V AC terminals. This AC voltage is converted to DC by diode D1 and filter capacitor C2 and is used to test the zener diodes. R3 is utilized as a series current limiting resistor.