How to Troubleshoot & Replace Whirlpool AP6784287 / W11256462 Microwave Diode

Replacing a magnetron in my particular 9-year-old microwave (a microwave/hood combination) was not a simple “plug & play” operation. That is why I am placing this in the slightly difficult area. First, it takes 2 people to remove the microwave from the top of the stove. Next the main outer panel need to be removed. After that, 2 sheet metal panels need to be removed in order to expose the high voltage components for testing. Always discharge the high voltage capacitor first before doing anything in the high voltage area. In my case, after testing with an ohmmeter, the magnetron was clearly shorted from the filaments to the metal case – that caused the HV transformer to buzz very loud. The HV capacitor was good, as was the diode and HV transformer. I replaced the diode anyway. Note that a standard ohmmeter in a typical DVM will show a good high voltage diode as open on both sides. It takes 9 volts or more to confirm a good or bad HV diode. A 9 volt battery works fine for testing. To gain access to the magnetron mounting screws, a plastic air baffle inside needs to be removed. After removing the 4 Torx screws, the magnetron can only be removed by tilting it back toward the oven cavity – no other way will work in my case. It is a tight area. After replacing the magnetron and diode, the oven now works great. It seems to heat things up faster than before. 

When the microwave stopped heating I took it off the wall and opened it up. I first checked the diode based on other people's stories online, and sure enough that was the cause. A diode should have infinite resistance in one direction, and low resistance in the other. Mine was completely open both ways, clearly it was burned out. Once the new one arrived it took just a few moments to install it and attach all the covers. Now the microwave works like new! Just be sure to safely discharge the capacitor before removing and testing the diode. As easy of a job as this is it helps to have a second set of hands removing and re-installing the microwave on the wall bracket for under cabinet installations. 

Replaced it. Hardest part was finding the tiny package at.my door. 

I ordered this part and it arrived the next day and now the microwave is back up and running! Happy wife....happy life! 

Replaced both the magnetron and diode. Very happy you had the part as this model is 15 years old but not ready for the pasture just yet 

Excellent! I saw the tutorial video and order the part.. Couple days later I had it installed and it work!! Only with a screw driver and I save 200 dls ! Thks 

I researched the problem. Found the solution online and ordered parts from AppliancePartsPros.com. It only took a screwdriver to make the repair. The only confusion I had is my model of microwave had a double diode, and the one sent to me (by model number) was a single diode. I wasn't sure what to do, either install the new single one or put the old double unit in. I went with the new single diode, and it works fine. I don't know why the two differences, but it all worked out. 

Replaced marathon and diode 

Replaced magnetron and diode 

Took it apart, replaced the magnetron and diode