Maytag 1150 watt Microwave

Discussion in 'Electronics Resources' started by just al, Aug 28, 2013.

  1. just al

    Thread Starter New Member

    Aug 21, 2013
    Model #mmv4205baw Trips breakers after heating for about
    30-40 seconds. Anybody have any idea why?
  2. LDC3

    Active Member

    Apr 27, 2013
    Yeah, the refrigerator starts up.
  3. Ramussons

    Active Member

    May 3, 2013
    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.

  4. #12


    Nov 30, 2010
    +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.
  5. sheldons

    Well-Known Member

    Oct 26, 2011
    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....
  6. studiot

    AAC Fanatic!

    Nov 9, 2007
    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.
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Assuming the fan is working and clean, I would replace the main HV cap.