BEFORE WORKING ON MICROWAVE, ALWAYS MAKE SURE YOU UNPLUG THE OVEN AND FULLY DISCHARGE THE HIGH VOLTAGE CAPACITOR.
On information on how to safely discharge the high voltage capacitor, please visit the link below:
How To Safely Discharge A Capacitor?
Testing the HV Rectifier Diode
A defective diode is either shorted or open.
To perform this test you will need a 9V multimeter with diode test feature or standard multimeter and 9V battery.
If your multimeter is equipped with the test diode feature,
However, the following resistance tests will conclusively reveal a diode that is shorted. In most cases, defective diodes, whether shorted or open, will show some physical signs of the defect, such as a burned crack, a blistered spot, or it may even be split in two. Also, a shorted diode will usually give off a pungent electrical burning odor.
1. Unplug the oven.
2. DISCHARGE ALL HIGH VOLTAGE CAPACITORS. (Procedure)
3. Carefully remove the lead that goes to the capacitor (the ground connection may remain attached)
4. Set the ohmmeter to read ohms at a scale of R X 10,000 or higher.
5. Measure the resistance across the terminals of the diode by touching the positive meter probe to the anode and the negative probe to the cathode (the cathode is the side that goes to ground, usually marked by an arrow, dot or stripe).
6. A normal diode, depending on make and model, should read about 50,000 to 200,000 ohms.
(Note:The polarity of the meter probes, with regard to forward and reverse bias readings, may be relative to the type of meter being used.)
7. Reversing the leads should produce a reading of infinity (open), unless there is a bleeder resistor across the diode, in which case the reading would show the [megohm] value of the resistor.
8. If continuity is read in both directions, the diode is shorted. If infinity is read in both directions, the diode is open. In each case the diode must be replaced.
In some models the diode is located inside of the high voltage capacitor. In this case, identify the diode terminal and perform the same test as above, measuring from the diode terminal to the capacitor’s metal case.
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