Fuse blowing...door switches OK
Yes, as DER says, you should unplug from AC and discharge the HV capacitor before before getting into any MW repair. In the old days we'd just crowbar the cap with a screwdriver (be sure the handle is insulated!). Nowadays manufacturers recommend discharging through a resistor, which results in much less spark.
Once you've confirmed a hard fault exists by replacing and blowing another fuse, there are a few simple things you can look for. A failed HV diode is usually accompanied by a very obvious burn odor. If the magnetron filament shorts to case, you will read low (<1-ohm) resistance between case and one of the filament terminals. Sometimes a sharp eye, ohm meter and wiring diagram will lead you to find a unique problem (pinched wire, loose screw in the works, etc).
Disconnect filament terminals from transformer to eliminate possibility that the transformer is the source of short. Don't be fooled by low filament resistance between the two terminals. Some good magnetrons will read ZERO ohms!
With the exception of fuse and HV diode, these parts are generally expensive compared to the cost of a new MW oven. Prices on magnetrons vary quite a bit though, so it's worth looking online or calling your parts store. Bad panel? This MW is almost certainly doomed.
You can't really afford to replace parts (even if you do the work yourself) without a highly certain diagnosis. Certainty is hard to come by, especially if the fail takes a while to occur or is intermittent,
Nonetheless, if you feel certain that you have found the defective part and have a sense of adventure, you might be able to fix it.
Jun 20, 2016 |