• ** 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

Jenn Air JMC8130DDW won't heat

petec

Premium Member
Joined
Jun 5, 2011
Messages
50
Location
ellington, ct
Model
JMC8130DDW
Brand
Jenn-Air
Age
1-5 years
Won't heat. Also, the carousel seems a bit jerky at times.

Here's a history. A few months back I had a house wiring issue. The neutral line coming in from the pole broke. This casused the center tap of the transformer on the pole to float. As a result, when I would run a heavy load, such as an AC, it would pull the 115 VAC on that leg down to about 65 volts. The other leg would go to 170!!!! This took out the washer, an old TV (good riddance CRT!!!) a radio, coffee maker and probably a few other things.

I did notice that before I diagosed the neutral issue, the microwave did seem to be losing a little off its fastball. This is understandable as it was probably running on 70 VAC. After the wiring issue was repaired the microwave ran like new again.....until this week. Now it appears the magnetron is dead. Everything else works. It just doesn't heat. I tried running it at 50% power and you can hear the transformer working overtime when it is trying to power the mag.

Before simply ordering the mag, I wanted to run it by you guys.

Thanks for this site. You've saved me countless dollars on other things.
 

rickgburton

Appliance Tech - Moderator
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Messages
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Does the mag tube have continuity? You normally don't hear the transformer when the tube is bad.
C-HV Testing.jpg
 

petec

Premium Member
Joined
Jun 5, 2011
Messages
50
Location
ellington, ct
Sounds like maybe it failed as a short rather than open. Or something close to a short. Is there another component involved? I saw a youtube video that mentioned a diode.
 

petec

Premium Member
Joined
Jun 5, 2011
Messages
50
Location
ellington, ct
I think I may know what killed it.

The microwave is mounted in an island. When something is left on the island that dangles over the side, like a phone charging cable, it sometimes bumps the key pad, turning it on. This has happened a number of times and from what I know, running an empty microwave isn't the best thing for a mag. Could running in this condition have overheated it and caused a partial short of the element? This might explain the transformer working overtime.
 

rickgburton

Appliance Tech - Moderator
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I forgot that some smart phones and tablets won't show the images for this site.
 

petec

Premium Member
Joined
Jun 5, 2011
Messages
50
Location
ellington, ct
Well, everything looks normal with the exception of the diode. It appears to be open. Will this cause what I am seeing?
 

rickgburton

Appliance Tech - Moderator
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Yes it could. Usually when the diode goes out you'll hear a loud humm. The diode is actually a rectifier (4 diodes). Some of the less expensive meters don't have the ability to measure it unless there's a diode check function on your meter. You can check it with a 9 volt battery if needed.
Diode WPR9800486
Diode-WPR9800486-01136059.jpg

C-HV-Diode Test.jpg
 
Last edited:

petec

Premium Member
Joined
Jun 5, 2011
Messages
50
Location
ellington, ct
Its a pretty good meter, Fluke 87. It does have diode check setting. Pretty certain that is the problem I ordered the diode.
 

petec

Premium Member
Joined
Jun 5, 2011
Messages
50
Location
ellington, ct
Well, the diode didn't fix it. No change in symptom. It runs, but doesn't heat and the magnetron sounds louder than I remember. Is it common to have the diode and magnetron fail together?
 

rickgburton

Appliance Tech - Moderator
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It's rare to have more than one part fail at a time but it does happen occasionally. You're either missing something or you're not testing the components correctly. It breaks down to this: If the primary side of the transformer is receiving 120 VAC supply voltage and the microwave does not heat, the problem must be one of the high voltage components. The high voltage components are the transformer, mag tube, HV capacitor and diode.

The first thing you should test is the supply voltage going to the transformer and confirm you have 120 VAC. If the voltage measurement is correct, unplug the microwave and discharge the capacitor. Here's how to test the

Transformer:
C-HV-Transformer check.jpg

Mag Tube:
C-HV-Mag Tube test.jpg

Capacitor:
C-HV-Capacitor Test.jpg

Diode:
C-HV-Diode Test.jpg

A Fluke meter is good enough to make all measurements without a battery or jumper wires. Let me know which one is hanging you up.
 

petec

Premium Member
Joined
Jun 5, 2011
Messages
50
Location
ellington, ct
Well, I have finally gotten around to playing with this thing again. It looks as though I may have gotten a bad replacement diode. I did not measure it prior to installing, or if I did, I forgot as it's been awhile. Xfmr measures good. Cap measures good. I have 120VAC into xfmr. Diode is measuring open both ways.

Is it possible I have another failure that is taking out the diode?
 

Jake

Appliance Tech - Admin
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Aug 24, 2004
Messages
99,213
Location
McMullen Valley, Arizona
I found where Jeff said this yesterday:
We got to the point now if the mag is bad we include the diode, and if the diode is bad we include the mag as they can damage each other.
So you may want to order a new mag when you order another new diode.:)

Here's the mag for your model:
W10859575 Magnetron


Jake
 
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