On 14/05/2021 15:40, Peter Able wrote:
On 14/05/2021 13:31, Chris Bacon wrote:
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.Â* 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.

Thank you. OK, I disconnected at the magnetron, and there seems to be a
tiny resistance through the few red/black flecked fabric-covered coils I
can see in the middle of the transformer. Maybe 0.1 ohm, but my meter
isn't particularly precise.

Is there anything else to measure?


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

It's quite an old machine now, and I have heard that the fuses can go
after repeated uses.... coincidentally, I had just used "low power"
to simmer things; this seems to be full power but switched on and off
every so often....