What if the HV diode or capacitor are leaky?
An (electrically) leaky HV diode or cap would likely fail totally in short order since it would be dissipating a lot of power. However, until this happened, the oven might continue to operate and not blow a fuse. The effect on performance in both cases would be to reduce the effective voltage across the magnetron and thus the output power. I consider these sorts of failures somewhat unlikely as the HV diode and capacitor do not generally fail half-way! Testing the magnetron WARNING: First, with power disconnected, discharge the high voltage capacitor. See the section Safe discharging of the high voltage capacitor. • A magnetron with an open filament will result in no heat but no other symptoms. The bad connection may be internal (in which case the magnetron will need to be replaced) or external at the filament terminals (which may be repairable). • A magnetron with with a short between the filament/cathode and anode will likely result in a loud hum from the HV transformer and/or magnet
