• ** 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

    Jake

FIXED 721.85039111 Microwave makes a loud buzzing noise when door is closed

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southcinci

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Location
ohio
Model Number
721.85039111
Brand
Sears Kenmore
Age
1-5 years
Microwave makes a loud buzzing noise when door is closed, but lights work and it heats food

Makes a loud buzzing noise but heats ok and only does it when the door is closed.
 

jeff1

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Hi,

721.85039
That is part of a full model#...I found 721.85039010 721.85039011

Is the magnetron coming on when the door is closed but the fan/turntable is not running?....that may account for the loud noise as the mag will over heat without the cooling fan running. magnetron, high voltage transformer are common for making noises. A stuck/welded closed relay on the board would be a prime suspect.
Does the turn table/fan/light work if you set a cooking time?

jeff.
 

southcinci

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Reply to Question

Hi Jeff,
The turntable works, the fan runs, and the light works. It heats just fine. The buzzing occurs whenever the door is closed. It stops with the door open.
Thanks,
Drew
 

jeff1

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The turntable works, the fan runs, and the light works. It heats just fine. The buzzing occurs whenever the door is closed
So when you close the door the turntable, works, fan works, lights works but you get a noise.....but if you set a cooking cycle normally it doesn't make a noise? Can you record the noise?

jeff.
 

southcinci

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Microwave makes loud buzzing noise

I am out of time for a couple of days but should be able to record sound. But I think the sound is still there while cooking food, but with the fan running it is not as noticeable. I tried to ease the control cover off, but there must be one screw I can't find holding it on. I thought I may be able to hear what part buzzes then take a picture. Thanks so much for your interest!!.
Drew
 

jeff1

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But I think the sound is still there while cooking food, but with the fan running it is not as noticeable.
That more and more sounds like the magnetron is coming on when the door is closed.

Still haven't seen a full model#.

I tried to ease the control cover off, but there must be one screw I can't find holding it on.
Normally the upper grill accross the top comes off and has a screw at/near the top of the consol....

F1010033-00002.jpg

F1010033-00003.jpg

....then we lift up and the consol will tilt open towards us.

jeff.
 

southcinci

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Messages
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Location
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I am out of time for a couple of days but should be able to record sound. But I think the sound is still there while cooking food, but with the fan running it is not as noticeable. I tried to ease the control cover off, but there must be one screw I can't find holding it on. I thought I may be able to hear what part buzzes then take a picture. Thanks so much for your interest!!.
Drew
I made a video of the sound, hopefully you can hear it. Sorry it took so long to reply. Thanks for your patience!

[video=youtube_share;GbjvRZg8fMo]https://youtu.be/GbjvRZg8fMo[/video]


Kenmore Microwave label.jpgKenmore Microwave label.jpg

Hopefully the attachment of the label comes through on the thread.
Thanks
Drew
 

jeff1

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721.85039111
That one works.

That buzzzzing noise is the magnetron firing up.
Sounds like ( no pun intended ) the board is welded closed and we may also still have a door switch/door switch mechanism isssue also.

jeff.
 

southcinci

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Kenmore Microwave

Should I try and replace the board? Is it worth fixing. It's only two years old.
Thanks,
Drew
 

jeff1

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Thankx for the update :)

jeff.
 

fshrmkmn

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Location
CT
Hello. I have this same problem described with the magnetron coming on when the door is closed. Same symptoms described. My microwave is a Kenmore model number: 40185052010 . I cannot find much info on this model number and cannot find any power control board part online. Any advise? Thanks in advance.

- mike
 

jeff1

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I have this same problem described with the magnetron coming on when the door is closed.
Check door switches first.
If ok, board is then suspect.

I cannot find much info on this model number and cannot find any power control board part online.
Appears to only come complete....#73....

50037507-00001.jpg

No pic LINK> Assy control box

jeff.
 

mvanstory

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Location
United States
I have the same exact buzzing - Kenmore Model 721.67909601

Hello Jeff-

Thanks for the help on this stuff! I'm amazed that I found this exact problem thanks to the microwave video. I think this may have been caused by a family member over during thanksgiving that put a plate (with a metal ring around it) in the microwave. Not positive though.

So it looks like I have the magnetron problem as well. Do you think I also need a new power control assembly?

Thanks a ton.

-Mike
 

jeff1

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Hi,

I have the same exact buzzing
When?...as soon as the door is closed....when the cooking is suppose to be occurring?

jeff.
 

jeff1

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So it looks like I have the magnetron problem as well.
Nope. ( other than it shouldn't run as soon as the door is closed )

Do you think I also need a new power control assembly?
Not yet. Check the door switches, door switch mechanisms first.
Top switch should open when the door is opened.
Middle switch should close when the door is open.
Bottom switch should open when the door is opened.
If ok, then yes the board would be the suspect.

jeff.
 

jeff1

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A bad switch is more common yes....both can and will fail but we see more door switch issues than anything else.

jeff.
 
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