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.