Yes Magnetrons can flash over and fail. Usually they get air in, or get
carbonised somewhere, however when I could see the usual suspects were the
transformer or the diode.
Some of the more complexes ones with a lot of electronics can just fry
their control boards, sadly, Toshiba were good at that.
Brian

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"jon" wrote in message ...
On Fri, 14 May 2021 13:31:48 +0100, Chris Bacon wrote:

So it was making an odd noise, and not heating the food, light comes on,
steel turntable revolves, beeper sounds at end of cook time.

Check HV fuse. Blown. Aha, replaced, it's done that before, should be
OK... but no! Food still cold, fuse blown again.


Check the diode (CL04-12) using a multimeter on 20V setting and 9V
(actually 8.34V) battery. 0V one way, 3.26 the other. A bit low?

Capacitor: No connection (meter on 2000k ohms setting) between either
terminal and case. Between terminals resistance increases from zero to
infinity over a second or so.

Magnetron: Meter set to 200 ohms. 0.5 ohms between terminals either way.
Meter set to 2000kohms, no connection between terminals and case.

High voltage transformer: Primary, isolated, about 2.2 ohms. Secondary
150. There is another winding that seems to go to the magnetron, I don't
know what this is.


So any help on what's up, and what to do about it?


Try another magnetron.