What are the methods for judging whether the diode rectifier bridge is good or bad?
1. Short circuit open circuit test
Turn the function and range switch to the buzzer position and the two probes are separated from the test point. If a short circuit occurs, the buzzer will sound.
This method can be used to test the on-off condition of the circuit. It should be noted that the buzzer does not necessarily indicate a short between two points. If the resistance between the two points is small (20Ω), there will also be a sound.
2. Inductance test
Put the multimeter in the resistor position, then connect the red and black probes to any front end of the color-coded inductor. At this point, the pointer should swing to the right. Based on the measured resistance values, the following three conditions can be distinguished in detail:
1. The resistance value of the measured color-coded inductance is zero, and there is a short-circuit fault inside.
2. The DC resistance value of the measured color-coded inductor is directly related to the diameter of the enameled wire and the number of winding coils. Color-coded inductors tested are OK as long as the resistance value can be measured.
3. Polarity, quality and voltage test of common voltage diodes
(1) Polarity judgment of Zener diode
A Zener diode is a diode that operates in the reverse breakdown region and has a stable voltage. Its polarity and function are measured similarly to ordinary diodes.
(2) Zener diode test
If the forward and reverse resistance of the Zener diode measured by the pointer multimeter is small or infinite, or the voltage measured by the digital multimeter is small or large, it indicates that the diode is damaged or damaged by an open circuit. circuit. When the Zener diode is stable, if the measured stable voltage value is high or low, the diode is not stable.
(3) Measurement of stable voltage value
Using 0~30V continuously adjustable DC power supply, for the Zener diode lower than 13V, the output voltage of the Zener power supply can be adjusted to 15V. Connect the positive terminal of the power supply in series with the 1.5k current limiting resistor, then connect it to the negative terminal of the Zener diode. Connect the negative pole of the power supply to the positive pole of the Zener diode, and then measure the voltage across the Zener diode with a multimeter. The measured reading is the voltage value of the Zener diode regulated voltage value. If the regulated value of the zener diode is higher than 15V, the regulated power supply should be adjusted to more than 20V.
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