Model #mmv4205baw Trips breakers after heating for about
30-40 seconds. Anybody have any idea why?

 

Model #mmv4205baw Trips breakers after heating for about
30-40 seconds. Anybody have any idea why?

Yeah, the refrigerator starts up.

 

Model #mmv4205baw Trips breakers after heating for about
30-40 seconds. Anybody have any idea why?

The Magnetron in the Mirowave is cooled by a fan blowing air over its cooling fins. If the temperature exceeds a set level, a thermostat on the magnetron will trip and shut down the oven.

Check if the cooling fan operates.
Check if the Magnetron cooling fins are clean.

Check if the Magnetron gets too hot in spite of the above.
If Mag not overheating, by pass thermostat and try again.

If tripping occurs again, the likely suspect is the Magnetron.

Ramesh

 

+1 on Ramussons

It is very hard to diagnose something just because you said it stops, but the only things that use enough power to trip the circuit breaker are the magnetron and the transformer. The fact that it takes most of a minute to fail leads to what Ramussons said.

 

another possibility is the monitor interlock playing up but even so the mw completely switches itself off or trips a breaker? i also had one with a faulty turntable motor witch did a similar thing....usually if the fan doesent drive air over the cooling fins on the mag the thermal cut out on the mag should disconnect the supply to the mw until it cools down and resets not trip breakers....

 

Is your microwave very heavy at one end?

Yes? Then it has a transformer as #12 says.

If it is quite light and well balanced it probably has an smps instead of the transformer. These can go faulty and cause this effect.

If you have a transformer, then you also have a large high voltage capacitor, probably with internal bypass diodes. These can also cause cutout after a short period.

 

Assuming the fan is working and clean, I would replace the main HV cap.