On 14/05/2021 13:31, 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.


Magnetron filament winding, connected to the two magnetron terminals.
Disconnect at the magnetron and check that this transformer winding and
the magnetron filament are OK (fraction of an ohm - but not zero). One
side of the filament circuit will be connected to the diode's anode. The
other magnetron connection (its anode) is via the magnetron's body. The
transformer HV secondary should have one end connected to the
transformer body, the current path between this and the magnetron anode
being via the chassis.

A blown filament shouldn't blow a fuse, though. Slightly worrying that
the fuse has blown before !

PA