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kenmore microwave model 79080333310 - fully dead

Hello,

Trying a first time DIY kind of repair.

The microwave stopped working in the middle of heating while there were 2 mins. still left in the heating cycle. Two of the GFCI switches got turned off because of this and I had to reset them to have them working again. The microwave is fully dead since then. No light, no display. I checked the power outlet with a lamp and it works fine. I checked continuity on line fuse, the three switches (1 and 3 continuity on door closed and 2 on open) and they are working as expected. I tested both thermal fuses on the frame and one showed continuity. I read that the other one is normally open. So I suspected this might have gone bad and replaced it. Plugged microwave back in and still nothing. I am out of ideas what else I can test.

Here is the link to the product parts page which has the part info and circuit diagram.

Thanks in advance.

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Hi @abitt ,

For the microwave to function, power needs to be applied to the control board. It then connects the power via relays to the various components as required.

Looking at the wiring diagram, power passes through a line filter (did you test that?) and then on to the L.V. (low voltage) transformer on the control board.

For a GFCI to trip means that there was current flow between the active leg and earth when there shouldn’t be, so you may have to also test for that as well (faulty HV transformer?).

Here’s a link that may help as it shows how to test most of the functions in a microwave oven.

Be safety aware when working in a microwave oven. The HV capacitor can store >5000V DC for months even if the power has been disconnected for this length of time. This amount of voltage can seriously injure you. The HV capacitor needs to be discharged correctly as soon as possible after removing the cover from the oven and before commencing any other work.

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