• ** 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 JVM1440WH04 GE Microwave not heating

kyferez

Premium Member
Joined
Mar 19, 2020
Messages
8
Location
GA
Model Number
JVM1440WH04
Brand
GE
Age
More than 10 years
Hi all, GE over the stove type microwave not heating. It acts like it's working, just no heat.

I have tested everything I can find, the thermal fuses (3 of them) door switches (3 of them, 2 NO 1 NC), diode, cap, transformer, and magnetron all per this video:
except the diode as my meter is auto ranging and wouldn't work on the diode at all in ohms mode. So I used the 9v battery test from this video:

So everything tests out ok, and I have 120V at input of the Transformer, no transformer shorts, coils test good at well under 1ohm on primary and secondary and no shorts to case, magnetron tests good well under 1ohm and no shorts to case, cap tests good as per video and no bulging. and Diode tests good at 6.5V with no leakage.

Edit: Also I don't see any cracks on the Magnetron magnets or ceramic.

So Anyone have any ideas? It's 25 years old but trying to conserve $ right now!

Added model number
 
Last edited by a moderator:

rickgburton

Appliance Tech - Moderator
Staff member
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Jul 11, 2006
Messages
38,220
Location
Murray, Utah 84107, United States
..... I have 120V at input of the Transformer ..... 1ohm on primary and secondary
120 VAC across the primary windings on the HV transformer and not heating would indicate a HV part failure.
C-HV-Trans.jpg
 

kyferez

Premium Member
Joined
Mar 19, 2020
Messages
8
Location
GA
Thanks, I did realize it's something on the HV side. I've retested all components as well - same results. I've reconnected everything and tested in hopes it was a bad connection - still not heating.

The issue is that with everything testing ok, I don't know what to do. I don't want to replace all 4 components: diode, cap, transformer, magnetron, as then I might as well buy a new microwave. But without knowing what to replace what other option is there?

I was looking for some guidance or recommendations from someone experienced with microwaves who might have had this situation before where everything tested ok.
 

rickgburton

Appliance Tech - Moderator
Staff member
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Messages
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Murray, Utah 84107, United States
OK, lets go over the testing again. I posted the diagram of the transformer because you said you had less than one ohm on the secondary windings. If that's true, the transformer is bad. That seems like a good place to start. Also, when measuring the voltage to the primary side of the transformer are the wires connected or disconnected?
 

kyferez

Premium Member
Joined
Mar 19, 2020
Messages
8
Location
GA
I said Secondary - it's what your image has listed as filiment - goes to the magnetron. The HV cap line reads 120ohms.
 

rickgburton

Appliance Tech - Moderator
Staff member
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Messages
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Location
Murray, Utah 84107, United States
Last edited:

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
38,220
Location
Murray, Utah 84107, United States
.... except the diode as my meter is auto ranging and wouldn't work on the diode at all in ohms mode
Your meter has a diode check function and audible continuity function. It looks like this:
symbol.jpg
Set your meter on the diode check function and touch the red lead to the anode and the black lead to the cathode. Meter should indicate closed or continuity. Reverse the leads on the diode and the meter should show open or no continuity.
C-HV-Diode Test.jpg

Touch each capacitor terminal with one test lead and the capacitor case with the other test lead. Any reading other 1 (open) the cap is bad.
C-HV-Capacitor Test.jpg
 

kyferez

Premium Member
Joined
Mar 19, 2020
Messages
8
Location
GA
My meter, similar to many, doesn't produce enough voltage in diode check to overcome the high bias voltage needed to test high voltage diodes, so I cannot perform the first one.

You have no text for the second image. But it is testing resistance with the 9v battery?! Couldn't that damage a meter set in ohms mode as it creates a short thru the meter when the diode is positioned so it's conducting? I did this test with meter reading Vdc and got 6.5v forward bias with no leakage in reverse.

Testing each cap lead to case it tests ok, no short.

Testing cap in capacitance mode on dmm, tests good at 880nF and cap is marked as 0.86uF.

Testing cap as shown in 3rd pic with dmm in resistance mode also tests good.

Testing cap as for 4th pic also tests good.
 

kyferez

Premium Member
Joined
Mar 19, 2020
Messages
8
Location
GA
Model number of what? If the microwave, I haven't been able to find it on it anywhere, Though it has schematics in a pouch in it if you want those pics.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
38,220
Location
Murray, Utah 84107, United States
Model number of what?
Microwave. Ge model numbers are usually around the door jamb or inside the oven cavity. If you can't find it, replace the mag tube. It's the only HV component that can test good but still be bad. If you're confident you tested the other HV components correctly it's the only part it can be.
 
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