Question about GE JVM1440 Microwave Oven

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HV diode producing resistance of 10 ohms.

Just tested the diode, transformer, capacitor, and magnitron in my GE jvm1441bh. Everything checks out but the diode.

The gallawa website says to set the ohmeter to read ohms @ a scale of R X 10,000 or higher. My meter just has one setting of 4000 ohms, which I suspect is just an auto range of 0 - 4000, so I'm afraid it isn't capable of reading resistances in the 50,000 - 200,000 range.

If that's the case is my multimeter simply providing a bad reading for the diode? It's reads 10 - 11 ohms across the anode/cathode.

Sorry for the ignorance, just not too familiar w/multimeters.

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  • dave_demaree Mar 07, 2009

    Appreciate the reply bob. Just a quick question.

    The gallawa site says that as long as you have a mm that utilizes a 6 volt battery or greater, you're ok. Mine uses a 9 volt battery.

    The website doesn't mention setting up a test circuit, just attaching the probes to either end of the diode and reading resistance. Is that not correct?

  • dave_demaree Mar 08, 2009

    Thanks for the clarification Bob. This microwave is only 3 years old, so I will have to use your method. To clarify, are you just hooking the diode in series with one of the battery terminals, then attaching the mm probe to the free end of the diode, and attaching the other mm probe to the free battery terminal?

    I tried that and I got a reading of 9.3 v both ways. When hooking the diode in parallel with the battery terminals, I got a reading of 5 volts one way, and three volts when reversed.

    Would this denote a faulty diode?

  • jpal012 Mar 26, 2009

    I have a jvm1440 ge microwave that doesn't heat the food but everything else works.The capacitor did not spark when I went to discharge it.I used your diode test with the 9volt battery . It tested good. The fuse also tested ok. I would like to test the transformer but I havent found a good test method yet also its pretty buried in the oven. If you know a good transformer test I would definitly be interested. Thanks



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You cannot check a microwave diode with just a mutli meter . you have to make a test jig take a 9 volt battery and a meter with dc volt scale set up the meter just like you would test a 9v battery .with me so far ? now remove one lead from the battery and insert the diode between the battery and the test lead .......take a reading . now reverse the diode take a reading ........ i just tested a diode before writeing this and this is what i got my battey volts where 9.2 v whith the diode inserted i got 7volts . reversing it i got .02 volts dc . a diode is a one way valve and mine is good because it passed curent only one way ...yours should be about the same ....... if you understand this please leave me 4 stars ! i even went out in the shop and tested a diode for you just to make sure my answer was correct

Posted on Mar 07, 2009

    BOB BROWER Mar 08, 2009

    there was a change in diode type . i for got to ask you how old your microwave is . if your microwave was made before around 1985 you can use the meter with the batterys inside . if it was bade after around 1986 its a very hv diode and will require the 9v battery test jig ..... there where 3 changes to the diodes 1966 to 1972 test with any meter 1973 -1986 any swing meter with 6 v battery (do not use digital) 1986 to present must use special equipment or homemade eqipment with 9v battery or higher and a dc volmeter ....... hope this helps , sorry i did not know you had an older microwave , i dont see them anymore in my shop and forget there are a still a few out there .... good luck

    BOB BROWER Mar 08, 2009

    the diode is in series with one battery connection and a meter lead eather one will do . then turn the diode over , you should be reading the battery volts through the diode



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I'd say your diode is bad but your capacitor may be good. You need to test it further - as described below.

In order to get reliable measurements to make a determination about the condition of the components, each should have at least one lead removed from the circuit. If not, your meter will read the through the rest of the circuit - and not be limited to the diode or capacitor under test.

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Fan works,all controls work,---loud motor noise right side by transformer and does not heat anything.


Depending on your technical skills , there are basically 4 components which you can check than normally cause this type of error in a microwave.


Firstly , check to see if your microwave is fitted with a fuse. This will normally be located inside the casing and it is not very common for a microwave to have a fuse , so don't worry if you can't find one. If you are in doubt , let me know and I will look up to see if there is a fuse for you to check.

Open the casing of you microwave and look at the back right of the unit for the following.

HV Diode is located near the power supply and is identified with a symbol like in the picture below.


Check the diode for physical damage like a crack , bulge , burst or burned smell as they normally fail physically. To test , set a multimeter to test resistance at 10k ohms and test. A normal diode should read 50-200 k ohms. If not , replace the diode as it has gone. Remember that the polarity is important , so test it both ways (or put positive to anode of diode)

Next component to check is the HV Filter Capacitor. This component is a big circular steel tube on the board/mounted near the HV diode.
Locate and remove any leads going to the capacitor AFTER DISCHARGING THE CAPACITOR.

Now , set you multimeter to resistance again to the highest available setting. Now put it onto the terminals for a few moments (Should read infinite) and then switch the leads around. The reading should go to almost zero and then go back to infinite. Also test between each terminal and the casing (if not covered in plastic) and this reading should be also be infinity. This test might not work if your multimeter is digital and has a very high latency. If it's a good quality multimeter , it should work fine.

Also inspect the capacitor for bulges , leaking , a strong burnt smell or a crack and replace if any of the test fails. These capacitors are designed to fail at the top of the capacitor where steel is visible , so check here especially.

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Most of these components can be found or ordered at radio shack (diode and capacitor) or most any other electronics supply store or (magnetron). If not , contact the GE directly.

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