• ** 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 Kenmore Microwave/Hood Combo don't heat

red1958

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Nov 1, 2012
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54
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Model Number
721.80523500
Brand
Age
6-10 years
Hi:

I have a Kenmore 721.80523500 Microwave/Hood Combo that suddenly stop heating food. Everything else seems to be working ( lights, timer, turntable, keypad, etc. ). I opened the case to veify what was going on, and when i turned on the oven, I can hear a loud pop and was able to see a spark coming out near the area where the capacitor/diode are connected. It just happened the first time I start the oven after it has been disconnected from the outlet for a long time. I have checked the input to the high voltage transformer and it was 120 volts. I haven't checked the capacitor, magnetron or the diode yet and of course, I don't have a high voltage multi meter to check the output of the high voltage transformer. I understand I have to discharge the capacitor before I check it or the diode but I want to be sure how to discharged it correctly. I have to large insulated screwdriver I can use to short the terminals on the capacitor but need to know if I have to disconnect the wires going to the magnetron or the diode before I do this. Can anybody help me on this problem?
 

red1958

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Can anybody help me pinpoint why the microwave is not heating the food? Thanks for any help on this.

Best Regards
 

jeff1

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red1958

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OK Jeff. I will try that and see if I got high voltage all the way to the magnetron ( I am not going to measure the high voltage, just short the capacitor terminals ). Do I have to remove the capacitor from the bracket or just short the terminals with the capacitor in place and the oven unplugged? Do I have to disconnect all the wires ( including the one for the diode ) from the capacitor terminals in order to short the terminals? Thanks for your help.

P.S. - I will try to use my celular phone video camera to try to record the spark I am talking about.
 

jeff1

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Do I have to remove the capacitor from the bracket
Nope.

or just short the terminals with the capacitor in place and the oven unplugged?
Correct.

Do I have to disconnect all the wires ( including the one for the diode ) from the capacitor terminals in order to short the terminals?
Nope.

jeff.
 

red1958

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Hi Jeff:

I was able to check the diode using two different ohmmeters ( a craftsman cheap one and a Fluke 87 ) and it looks like the diode is not short out but open. I use the Fluke in both the ohms different scales ( ohms, K ohms, M ohms ) and also in the diode test only and did not get any reading on it. Is it possible that the loud pop I was hearing happened if the diode is open? I also checked the capacitor and it seems to be working OK ( ohms reading goes up and down depending on the polarity I connect the test leads. Should I look any further on this or just replace the diode. Thanks.
 
Last edited:

jeff1

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Diodes can fail, but you need a really high end meter to test them.
No harm is trying one.

Diode-6021W3B001U-01057733.jpg Microwave diode assembly

jeff.
 

jeff1

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Please do keep us posted.

jeff.
 

red1958

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Hi Jeff:

I installed the diode but still there is no heat in the microwave. I rechecked the diode, the magnetron and the transformer voltage output. The reading on the magnetron is around .2 ohms on the terminals and is reading infinite from the terminals to ground. The transformer secondary voltage is around 2250 volts to ground with the conector of the magnetron disconnected from the magnetron. I also checked the cook sensor assembly and was getting around 2.3 kohms with the oven unplugged. When I hit the addminute button to heat some water I had in the microwave, the oven start the timer and after 15 seconds I heard something ( like if the magnetron was aching ) but I was unable to see where it was coming from because I was recording the area close to the diode and the capacitor. It just did this aching the first time. After that first time the timer went the whole minute without incidente, except of no heat. Any help?
 

red1958

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Hi Jeff:

I installed the diode but still there is no heat in the microwave. I rechecked the diode, the magnetron and the transformer voltage output. The reading on the magnetron is around .2 ohms on the terminals and is reading infinite from the terminals to ground. The transformer secondary voltage is around 2250 volts to ground with the conector of the magnetron disconnected from the magnetron. I also checked the cook sensor assembly and was getting around 2.3 kohms with the oven unplugged. When I hit the addminute button to heat some water I had in the microwave, the oven start the timer and after 15 seconds I heard something ( like if the magnetron was aching ) but I was unable to see where it was coming from because I was recording the area close to the diode and the capacitor. It just did this aching the first time. After that first time the timer went the whole minute without incidente, except of no heat.
 

jeff1

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red1958

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Hi Jeff:

I used a voltmeter with a high voltage probe to check the voltage coming out of the secondary of the high voltage transformer. I got around 2300 volts going into the Magnetron. I checked the magnetron specs and it said it is a 4.1 kvolts magnetron for my oven. Am I getting the right amount of high voltage to the magnetron? The capacitor/diode circuit should works as a voltage doubler ( if I understand the circuit correctly ) but I am getting around 1875 volts on the capacitor side that is not connected with the diode and 2300 volts in the other side of the capacitor where the anode of the diode is located. Do I have a bad capacitor? transformer? magnetron? What else should I checked? I am running out of options here. Thanks for your help.
 

jeff1

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Not meter testing....try the spark test and let us know what happens.

jeff.
 

red1958

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Hi jeff:

I disconnected the two primary wire of the transformer and connected a lamp to them. Lamp works on and off with the power set at 50%. Seems to be OK.

Remove two wires from the magnetron and apply power for 5 seconds. Turn off power and discharged the capacitor. Good crack and spark out of it. Seems to be OK.

Reconnected the two wires to the magnetron. Apply power to the oven. No heat at all.

Hope this help.
 

jeff1

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Turn off power and discharged the capacitor. Good crack and spark out of it.
That means the system is creating high voltage...but the mag is not using it.
Also since you hear a noise, might be a good idea to check the stir blade where the energy enters the oven....make sure no arc marks or food spatter there.

50027659-00006.png ( 5014 is the blade - 5044 is the cover )

Magnetron-6324W1A001M-01057951.jpg Magnetron - that not good, says Not available

jeff.
 

red1958

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Hi Jeff:

After many hours trying to find the Magnetron, I finally found a used one through a friend of mine. I received it and installed it. The microwave is back in bussiness. Thanks a lot for your help.
 

jeff1

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Thankx for the update :)

jeff.
 
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