Microwave

I don't recognise that model (I am in the UK) Is it an "inverter" HV PSU?

If so, have a close look at the magnetron magnets. I bet one or both of them are cracked from overheating.

If you just replace the Mag, it will work for a while, but it will probably fail again due to being over-run.

So it's a replacement Magnetron and a replacement inverter, Panasonic don't encourage you to repair this item, bur if anyone has, I would be interested to hear.

I recommend people stay away from these models, and go for a conventional HV transformer type.

Maybe magnatron overheating opening thermal fuse. Is the fan working? Maybe mag bad getting too hot. Does the display stay lit when it quits?

Yeah,I got stitched up with this model [AN772] HV blew a transistor in the inverter board and PAN wanted 160 pounds to repair it! Seems that the whole inverter board needs a replacement[if you exchange your board] All this for one transistor s/c.As a qualified[if retired]Microwave engineer Pan finally agreed to supply an exchange board for 90 pounds plus VAT. I refused as it is likely to fail again,and bought a Sharp Combi for

Totally agree with you about the Panasonic's. Mind you, the Sharp R-XXX models have their own issues don't they? I am of course referring to the CPU (digital display) which seems to fail sooner or later in nearly 100% if them, and at GBP39.02 (for most of them) one is left wondering if Sharp deliberately built in some unreliability. (call me a cynic)

I have worked on a bunch of these and have seen several problems . The first ones i saw had mostly one of those long square hi voltage diodes shorted , then i stared seeing the big 4 lead diode all shorted . I have seen a few with one capacitor split open and shorted transistor . These were all the first models large black ones and med sized white ones using the same board .

Now i see the big ones with a mirror like door , very nice looking oven . many of these got samsung mags put in them and i saw these bad often causing the thing to shut off in 6 seconds or so . These also had a defect in the plastic door latch where the spring would fall off because a plastic part in the door would break off ( to small ) easy fix

Check the door safety interlock microswitches. There are usually two of these. One is normally open and closes when the door is closed, but the other is normally closed and opens when the door is closed. It is this second switch that creates a straight short across the magnetron and must open or else you will blow the fuse. It could be welded contacts, or simply a misalignment of the door causing it to stay closed. You should be able to verify this with an ohmmeter or by temporarily disabling the safety interlock. If you get it working, remember to replace the switch since it is there for good reason.

Good luck.

Bob

Door switches are working fine and if they wouldn't they would still blow the fuse even if the inverter board is not connected, because the short is created straight from the relay that powers up the inverter board.

When I last had this same fault, the big power transistor on the inverter PCB was collector-gate short-circuit.

(This device is an IGBT so I don't mean collector - base)

I did consider repairing the board but I couldn't find a supplier for the transistor, and I didn't discover whether the board had suffered any other damage.