• ** 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
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FIXED KHMS147KSS0 Loud droning sound coming from microwave, (video), smells a bit like something burning

jokken

Premium Member
Joined
Dec 10, 2016
Messages
25
Location
NJ
Model Number
KHMS147KSS0
Brand
KitchenAid
Age
6-10 years
hi all,

there is a loud droning sound coming from microwave when it is turned on. Also something smells a bit like something is burning

it doesn't happen right away, the lights and fan do turn on for 1 second before the sound starts.

can you identify the issue please. hopefully you can see the video

[video]http://www.jokken.com/downloads/VID_20161208_213725164.mp4[/video]
 
Last edited by a moderator:

rickgburton

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jokken

Premium Member
Joined
Dec 10, 2016
Messages
25
Location
NJ
sorry for the delay the model # is: KHMS147KSS0
thank you for the advice I will check the diode and HV capacitor, I will discharge the capacitor first too!
 

jokken

Premium Member
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Dec 10, 2016
Messages
25
Location
NJ
hi again,
our microwave sat in the basement for months. and since wife only complained about it 10 or 20 times I didn't get right to testing it. : )
but the empty hole above the stove did bother me. i finally got to looking at this today.

i think we have a bad diode. it was the part that gave me the most confusing readings. everything else was very on par with the diagram.

diode testing results:

red lead -> anode
black lead -> cathode
ohmmeter shows 1.5M

black lead -> anode
red lead -> cathode
ohmmeter shows 180K (once in awhile I was seeing 0L which confused me)

using the 9V battery as confirmation
Forward Bias showed 5V not 1.4V
Reverse Bias showed .002V

im not sure what to make of those readings. but I guess it is the diode that is bad. what do you guys think!?

thanks!!
 
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rickgburton

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If your meter has a diode check function you'll read open in one direction and closed in the other direction. If you use a 9 volt battery you're measuring resistance not voltage.
Diode WPW10492276
 

jokken

Premium Member
Joined
Dec 10, 2016
Messages
25
Location
NJ
thanks Rick for the response
I bought the diode for $10 and replaced it. I was hoping to be able to come back and post a success.. but I still have the same issue loud droning and burning smell when running.

seems it was not the diode.

although now that I've got a good view inside this thing I can see where the burning smell is coming from. it is coming from the magnetron
I see smoke coming off of it somewhere up by the woven metal gasket or by the filament terminals, i cant tell. here are some pictures of suspect spots on the magnetron
photo 1.jpg
photo 2.jpg

the multimeter shows just .1 ohms when I test between the filament terminals (sometimes .2)
what do you guys think?

thanks
 
Last edited:

jokken

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Dec 10, 2016
Messages
25
Location
NJ
ok, thank you. i got one ordered, i should have it in a few days. ill try it out and keep you posted.
does the woven metal gasket look bad or is that normal to discolor in time?
also is .1 ohms between the filament terminals too high, considering the guide says 0 ohms?
 
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rickgburton

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Are you reading your meter correctly? If you have a continuity function on your meter the mag tube should show closed or less than one ohm. .1 is less 1 is open and 0 is closed
 

jokken

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i hope i was using correctly. i was using the setting with the ohm symbol Ω
measured .1 between the filaments. on other subsequent readings it showed .2 sometimes.
do i that have it wrong?

regardless though, since this magnetron was smoking I did replace it. (see the pics of it above)
and now the microwave works!
thank you for the guidance!

when searching for a magnetron I did see that most places recommend replacing the diode at the same time of the magnetron. so, since I did put in a new diode already, I found a place selling a magentron without the diode and saved that got me a little bit lower price...

thanks again!
 

rickgburton

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If you look at the old tube the waveguide is cracked. You were using the meter correctly. Good job!
 

jokken

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Joined
Dec 10, 2016
Messages
25
Location
NJ
hi all, this repaired microwave worked well for almost 3 years! thank you again! (it was a bad magnetron back in 2017)
but now it has an issue again. I am hoping you can advise me again, please.
KitchenAid - KHMS147KSS0

it has stopped heating. it runs, the light goes on, and the fan runs, but I don't hear the magnetron at all. usually you could hear it cycle on and off, (also the light in the microwave would flicker briefly when it kicked on, and it no longer does that). Should I suspect the HV capacitor?

thank you!
 

jokken

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the HV side of the transformer (red wire at the bottom right of the picture) has 120VAC when the microwave is running. It doesn't have 120VAC when the door is closed but does when the door is open. (this is strange but I guess that's not important here) as long as it has 120VAC when the unit is running, right?
Looking further: at first I thought the door switches were causing an intermittent problem because i noticed the microwave/magentron did work but very intermittently.
But now I see the thermostat on the magnetron has seen better days. The connectors are very loose and a bit browned, even the wire is browned. If i wiggle it the magentron starts to work.
So you guys think I should just replace 4393943 thermostat?

on a side note: what functions do the 2 doors switches do? I think there are three total switches activated by the door, two at the bottom and one at the top. Since I was messing with them I want to make sure all 3 are still doing what they are supposed to

thank you!!

.
microwave.jpg
 
Last edited:

rickgburton

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the HV side of the transformer (red wire at the bottom right of the picture) has 120VAC when the microwave is running.
So you tried to take a measurement on the HV side of the transformer and you're not dead. Cool! The red wire and white wire connected to the transformer in your picture is the primary side and it sounds like the TCO on the mag tube is bad.


There's a primary interlock switch, secondary interlock switch, and monitor interlock switch. Remove the wires and check each switch for continuity by opening and closing the door
Microswitches.jpg
 

jokken

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oh right I should have said primary side not HV side!
lol it is cool that I'm not dead! and neither is this microwave. yet...

got the thermostat/TCO (is TCO Thermal Cut-Off?) in the mail and installed it. we are back in business! door switches are working correctly too. we are all set again, it is a lot easier to make hot chocolate for my son in the morning :)

thank you once again rickgburton!
 

jokken

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we are in North Jersey pretty near PA border (Delaware Water Gap). sadly I've never been out your way, pretty much have stayed on the eatern seaboard. hope to travel to other states someday!
 

rickgburton

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near PA border (Delaware Water Gap).
OK, right off I80, Warren County. I'm from Hunterdon county. I lived right below Round Valley Res. in Lebanon (Clinton, High Bridge area) Cool!
 
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