To check a rectifier diode for failure, first remove it from the circuit. Then, use a multimeter set to the 100×R or 1000×R ohm range to measure the resistance between the two leads of the diode. If the measured resistance values are significantly different, with the high resistance being up to several hundred KΩ or infinity and the low resistance being only a few hundred Ω or less, then the diode is good. If the measured resistance values are almost equal and the resistance is very small, then the diode has failed and must be replaced. If the measured resistance values are both infinite, then the diode is internally disconnected and must be replaced.
To replace a rectifier diode, you can use a diode of the same model or other models with the same parameters. In general, rectifier diodes with a higher withstand voltage (reverse voltage) can be used to replace diodes with a lower withstand voltage, but diodes with a lower withstand voltage cannot be used to replace diodes with a higher withstand voltage. Rectifier diodes with a higher current rating can be used to replace diodes with a lower current rating, but diodes with a lower current rating cannot be used to replace diodes with a higher current rating.
Explanation of Terms
- Rectifier diode: A diode that is used to convert alternating current (AC) to direct current (DC).
- Withstand voltage: The maximum reverse voltage that a diode can withstand without breaking down.
- Current rating: The maximum current that a diode can carry without overheating.
- Soft breakdown: A type of breakdown that occurs in a diode when the reverse voltage is below the nominal withstand voltage.
- If you are not sure whether a rectifier diode is good or bad, you can always replace it with a known good diode.
- If you are replacing a rectifier diode, be sure to use a diode with the same or higher withstand voltage and current rating.