Homemade zener diode tester circuit

Zener diodes are widely used in electronic products, such as voltage stabilization circuits and protection circuits in color TVs. In recent years, due to the introduction of a large number of foreign electronic products and components, it has been difficult to find the parameters of many Zener diodes, which has brought certain troubles to maintenance. In addition, when making and repairing electronic products, sometimes strict requirements are placed on the parameters of Zener diodes (such as Zener diodes in color TV protection circuits), which requires testing and selection of newly purchased or suspected Zener diodes. , so it is necessary to make a simple Zener diode tester. Now I will introduce to you a self-made zener diode tester for your reference and imitation. The circuit is shown in the figure. The parameters shown in the figure can measure the stable voltage value of a low-power Zener diode in the range of 0 to 250V. If the voltage stability value of the measured Zener diode is low, the secondary voltage of the transformer can be appropriately reduced. The voltmeter in the picture can be replaced by the DC voltage block of a multimeter. The transformer can also be replaced by the power transformer of a tube radio. I used a three-filament tube radio power transformer when making it. It should be noted that if the voltage stabilization value of the measured Zener diode is high, R2 in the figure must not be omitted, otherwise you may suffer an electric shock. In addition, if you find it inconvenient to use a button switch, you can also use a twist switch. When in use, connect the diode under test in the direction shown in the figure, press the power switch, and the stable voltage value of the zener diode can be read from the voltmeter. At this time, LED1 should glow green, indicating that the test is in progress. In addition, if the C and E poles of the triode are connected, the withstand voltage value of the triode can be measured. This device can measure tubes with a voltage of about 300V or less. Please note that the leakage current of 3AD tubes is large, so The measured value is obviously low. Of course, if you want to conduct simple tests on color TV tubes, etc., you can further increase the secondary voltage of the transformer, but the insulation during winding needs to be taken seriously.