Dead microwave oven

There are lots of different magnetrons out there. The chances of a random one from another microwave being compatible are very slim. If you open your machine up though and get the actual magnetron model/part number, the chances of being able to get a replacement are pretty high.

Tim

Looks like the magnetron is available from various sources at around £50

- 60 for a new one (I'd rather avoid anything on eBay!). I can test the diode:

Better dig out my well-insulated screwdriver and a decent 1+Mohm resistor first, though, to put across the HV capacitor. ;-)

A loud humming noise could be indicative of a transformer with a shorted turn.

Cause could be transformer, diode, HV cap, HV fuse, wiring or less likely magnetron. Diodes are the least reliable, I'd test that 1st. Of course it's wired to a cap that can hold enough charge to kill a queue of people.

Definitely dry out before testing. HV does not like damp.

HV Diodes are largely interchangeable, not if the donor diode is much lower power. Magnetrons often too, and often not. But it's not so likely to be a dead mag.

I put a couple of 1Meg resistors in parallel, and placed them across the capacitor terminals using a long insulated screwdriver. I know it's rather a lot of belts and braces as there's an internal 10M resistor in the capacitor to discharge it, but it's not worth taking chances.

The HV diode, capacitor, and transformer all tested ok. The magnetron had less than 500 ohms from the heater to earth, so it's failed. I could mess around changing the magnetron, but I think it's time for a new microwave oven anyway.

I genuinely thought there weren't that many. Where quite a few are interchangeable.

BICBW

Likely just the ceramic caps in the maggy failed.

there is probably only about 4 power levels and all the other variations are fitting arrangements.. I have a dozen of so, because I save the ring magnets.

I'll likely take it apart and save possibly useful bits like the capacitor and HV diode. Although the transformer is ok, I doubt I can make use of it, and the likelihood is that it won't fit another make. If I can get the magnetron out, I'll have a look and see if it's obvious what is responsible for the conduction.

The new MO is being delivered tomorrow.

The new one has just been delivered. It was ordered Thursday afternoon from ao.com, so very quick service. Before I try it I'm just letting it warm up to room temperature. I'd hope condensation wouldn't get inside, but I'm in no hurry to try it out. ;-)