MW was running with normal hum; hum got louder and MW stopped. Replaced fuse; turned on MW; fuse blew. Replaced magnetron; jumped fuse leads; MW ran a few seconds and tripped. Capacitor reads <1 kohms with power; 0 without power. Diode reads 0 both ways.
The diode test sounds like it failed and the capacitor test sounds invalid. The capacitor should be tested each direction, (polarity wise), and you should see a constant rise/drop to infinite reading. The best test for a capacitor is with an actual capacitance tester CT1. I think in this particular case, I would replace the diode and the capacitor. While your in there you should test the primary and secondary windings of the H.V. transformer. If the H.V. transformer fails it produces a low frequency growl.
Microwave dead. I changed out fuse #74 on diagram for control panel due to being tripped (conducted continuity test) and everything came back to life. Set clock and then tested micro by hitting 30 sec button which immediately tripped fuse #74 again. Thinking it is the HV diode and capicator?
Answer Hi Keebler. It will be best to open the cabinet cover. Then physically check the magnetron part # WB27X10017 and see if thetop pointed emitter tip is melted apart (off) also check the side magnets to see if they are cracked. The most common failure is that this part along with the diode part # WB27X1160 and the capacitor part # WB27X10011 are advisable to be replaced because they operate off one another in the same electrical circuit. The capacitor stores high voltage if not properly discharged before safe handling. See our link on proper discharge procedures. There is a door monitor switch that is designed to open the fuse part # WB27X10388 if it is shorted. It is part # WB24X830. Thank You.