Mmv4205baq is humming but wont heat 3 years old tested capasiter and get no needle move ment

If the control circuit turns on the power supply to the magnetron tube, the big power transformer should hum. Then after a couple seconds, it should hum louder as the magnetron warms up and starts to put out RF. If everything stays stone cold, the magnetron is probably shot.

These are repairable, and the parts are available. But you have to decide whether it is worth repairing. If it's past warranty, probably not. I am a radar transmitter engineer with 40 years' experience with these kinds of tubes, and if my ten year old microwave quits, I'm going to just throw it out (after I take it apart just to see what quit).

It's probably the internal fuse.You will have to take the microwave down so you can remove the housing to get at the fuse.(I will probably install an accessable panel mounted fuse holder if this ever happens to mine-already did it on the little microwave I carry around on my work truck to heat up my lunch).

That is possible but the parts are usually on the inverter board sold as a unit---Magnetron is also possible.

Hi,
Here is a tip that will help you to figure out what is wrong with yourMicrowave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101 ][
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if microwave is counting down but no heat you either have a loose connection at the magnatron tube or the thermal cut out fuse that is connected to the magnatron has blown or you have a micro switch, that has failed

When a high-voltage capacitor fails, it almost always shorts, which will cause the fuse to blow as soon as you hit "start" to begin cooking. So you can almost certainly rule that out.

A loud buzz, hum, or groan is usually a shorted high voltage rectifier diode, but a sound like gurgling into an empty coffee mug is one symptom of a failed magnetron, and yet the mag can be bad without that sound.

Here are some links you or someone you know can use (in order given) for test help, but read the safety warnings first:

http://www.gallawa.com/microtech/cap_test.html

http://www.gallawa.com/microtech/diode.html
(if it is NOT shorted or burned looking, it's probably fine)

http://www.gallawa.com/microtech/mag_test.html
(continuity can be good even though mag is bad!)

http://www.gallawa.com/microtech/xformer.html

You can find helpful exploded view diagrams and order parts by entering your full model number from the tag on the oven here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

From your description it sounds like the magnetron has failed in this oven. That's the part the makes the microwaves to heat the food. It typically fails by shorting out and making a loud hum noise. It not usually worth fixing since the price of a replacement magnetron is almost as much as a new oven.

This is probably a shorted triac or relay.

You can find exploded views and order parts by entering your model number at the Sears parts site.

There may also be a "mini-manual" (tech sheet) hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting, testing, and locating components.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

It does not heat.

I already replaced the HV diode. That did not fix the problem

It still has a loud hum and no heat. I'm guessing the magnetron.

The unit is six years old. I did not purchase it, the unit came with my house.

Model # JE1660MB002

hi,

You may need a new magnetron, contact sharp or the store you got it from; most microwaves have a 3-5 year warranty on the magnetron. If it's not in warranty, find a good appliance repairman, this is a difficult and dangerous repair job.