• ** REMEMBER! **The microwave can still shock you even unplugged!!

    ALWAYS discharge the high-voltage capacitor first if you even think your hands will come close to any HIGH VOLTAGE components.

    Jeff mentions this: Anything in the high voltage ( magnetron, capacitor, diode, wires to and from ):
    ...Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it.

    From Jeff's site: http://www.applianceaid.com/component-testing.php

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ME21H9900AS Microwave Transformer Bad?


Nov 10, 2018
Red Deer, Canada
Model Number
Everything works on my microwave expect it does not heat anymore. Just stopped working one day. Turn table turns, lights come on, controls are fine. Just wont heat food no matter how long it runs for.

I have tested the capacitor, diode, switches and temp sensors. All good. I have 120 volts AC going to transformer when running. I have it narrowed to transformer or magnetron.

The transformer when testing the HV side to ground gives 141 to 142 ohms. My research suggests it should be between 80 to 120. Does that mean my transformer is bad?

Tests on the magnetron seem good. There is some slight discolouration on the fins of the magnetron and there is a little noise from inside like a tinny sound if I shake it.

Please advise.


Hmm....Isolate and measure the secondary winding to transformer ground. 140Ω is too high.

There shouldn't be any discoloration on the tube fins and it shouldn't make any noise when you shake it.
DE26-00126A Trans

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