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Faulty Big Capacitor In Microwave Oven

By on January 26, 2015
microwave oven repairing











The Brand of this Microwave oven is Citizen Model No.: JM5598K. This appliance belongs to the Restaurante Romantico San Severino in Matanzas-Cuba:

microwave oven repair

The complaint was it switched on but when you executed any function, the fuse blowed right away, and they were using a piece of wire to substitute the fuse. This happened in Chritsmas Eve and they had not any other Microwave oven to substitute the broken one.

Note: never use a piece of wire to substitute a fuse.

First thing done was to disassemble the device; some screws of the upper cover were taken out.

microwave oven repairs

            When you face a situation like this, you should take a look at the high Voltage (HV) section:

microwave oven repairings

  • The HV diode was tested and it was fine.
  • The Magnetron was not short-circuited.
  • But the HV capacitor was shorted.

This capacitor of 1.00µF/2100VAC was extracted from the system.

microwaveoven capacitor

Two days later a new one was bought with a similar features: 0.95µF±3% 2100VAC, it was connected into the circuit. The fuse was substituted for another one with same features too.


When the equipment was powered on, look at the results in the photos below:


The Microwave oven really worked perfectly fine, the owner of the restaurant, who is my friend was very happy now.













This article was prepared for you by Humberto Rodriguez, one of our ‘Master Authors’ from Cuba.

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  1. Shekhar

    January 26, 2015 at 10:51 pm

    I have faced many times microwave front panel membran foil switches not working problem,& the original foil many times not available.
    In such cases I have done the micro switch mounting on inner side of the panel, the front switches sticker kept intact,& done the circuit by way of wiring.
    Its very time consuming job but on customers demand I did it in many models of LG, SAMGSUNG etc.

  2. g wells

    January 26, 2015 at 10:53 pm

    way to go ,i knew you could do it.

    • Humberto

      January 27, 2015 at 9:23 pm

      Thanks g wells. You are welcome

  3. Yogesh Panchal

    January 26, 2015 at 10:56 pm

    How did you test this three leg capacitor for short circuit ? on capacitor print it is showing resistor connected in parallel can you please explain;this is new for me.

    • Dan

      January 27, 2015 at 7:23 am

      In my experience dealing with Capacitors with a bleed resistor, the resistor is rated in MegOhms.... for all practical purposes, you shouldn't even "see" the resistor in circuit. A shorted Capacitor will read way below MegOhm range..... Hope this helps...

    • Humberto

      January 27, 2015 at 9:48 pm

      Well Yogesh Panchal, this capacitor only has two poles, a pole has two or three connectors, I tested it on with a Digital Multimeter in ohms scale, and it was shorted

  4. andre

    January 26, 2015 at 11:21 pm

    Now thats, should be a free lunch for sure , nice one.

    • Humberto

      January 27, 2015 at 9:48 pm

      Thanks andre

  5. Luis Estrada

    January 26, 2015 at 11:56 pm

    Hurra!, Humberto. Nice trouble shooting and quick repair. Gracias, saludos.

    • Humberto

      January 27, 2015 at 8:54 pm

      Hi Luis Estrada, thanks for your opinion.

      By the way, tanto su nombre como apellido son latinos, where are you from?


  6. Robert Calk

    January 27, 2015 at 12:13 am

    Good job Humberto.

    • Humberto

      January 27, 2015 at 8:58 pm

      Thanks Robert, your opinions are always very well welcome.

      Have a good day, Humberto.

  7. Kevin

    January 27, 2015 at 12:51 am

    Good find and a worthy repair. But, I see a metal pot in the unit. I thought metal in the microwave was a big no-no. Must be I am missing something.

    • Robert Calk

      January 27, 2015 at 7:39 pm

      I think that is just a reflection on the glass.

    • Humberto

      January 27, 2015 at 9:19 pm

      Yes you are right, this Microwave oven belongs to Restaurante Romantico san severino in Matanzas, Cuba

      They tested on the equipment and I did not realized what kind of pot was put into the oven.

  8. colin

    January 27, 2015 at 2:48 am

    same fault can be caused by a faulty door switch as well,the faulty switch is normally the switch with 3 wires connected to it

    • Humberto

      January 27, 2015 at 9:00 pm

      you are right colin

  9. Andre Gopee

    January 27, 2015 at 3:35 am

    Great work Humberto. Substituting fuse with wire can be very dangerous and can cause fire.

    • Humberto

      January 27, 2015 at 9:02 pm

      Ok, Andre Gopee, fuse have to be taken into consideration in all kind of appliances.

  10. mohammed

    January 27, 2015 at 3:36 am

    thank you mr yong , and thank you mr Rodriguez for sharing this repair.
    mohammed from KSA

    • Humberto

      January 27, 2015 at 9:05 pm

      Thanks to you too mahammed, your opinion counts too

  11. Mohammed Kasim

    January 27, 2015 at 8:40 am

    Thanks for the wonderful article. I heared that there will be a heavy shock from microwave oven while repairing with out knowledge. I hope it is from this capacitor.

  12. Arthur

    January 27, 2015 at 10:39 am

    This side of the microwave is "soooo familiar" to me... I spent several years working on microwaves and other home and restaurant appliances and equipment. I grew up with a dad in electronics, TV's radios, airplanes and their eqipment. And yes, if someone is working on a microwave oven - if any way possible, obtain a "Leakage Meter". Check the unit out for "Microwave Leakage". It Does Exist. I have personally spent at least one day being sick and feeling it. I was working on a unit - in a repair shop in my hometown of Tulsa, Oklahoma years and years ago. My boss hesitatingly purchased a leakage meter and I used it to check an over I was working on. I felt nauseous before I got the meter and after I took a leakage reading and showed it to my boss, he was glad we had it. But unfortunately, I did have to scrap a few microwave ovens over time because they did leak. If you think your "Magnetron" is bad or find it is bad....DON'T TOSS IT IN THE GARBAGE. Try calling a local "Hazardous Material Handler" and ask them where you can dispose of "the most dangerous part of the microwave oven".

    • Humberto

      January 27, 2015 at 9:08 pm

      Ok Mr. Arthur, I'll take your advise.

    • Amir Mukhtar

      January 28, 2015 at 5:35 pm

      Thanks you Mr. Arthur

      Also, Please Inform us about Leakage meter Specifications if Someone want to buy good one.

      thanks you for your Precious Advise .

      Amir Mukhtar Ashrafi

  13. Beranrd D'Costa

    January 28, 2015 at 1:51 am

    Dear Humberto , Ola , Sir I enjoy your articles tremendously and find them informative I have a few Questions if you dont mind
    you said... •The HV diode was tested and it was fine. Pls explain how it was tested ? (HV )range ?

    •The Magnetron was not short-circuited. pls explain, how did you test and confirm the same

    •But the HV capacitor was shorted. I had a similar question as Yogesh but he ws given an explanation in a following answer ... still pls explain how the same was tested ...


    best regds bernard/~

  14. aword stephens

    January 28, 2015 at 8:13 am

    thanks for the boost ,,,,but i have one it lights up but there is no function of the power button nor some of the other button,,please tell me what to do

  15. Amir Mukhtar

    January 28, 2015 at 5:30 pm

    The Above Article Was Nice and Learnable for every Repairer.

    Thanks you Humberto Rodriguez, and Sir Jestine .

    A Student of Electronics
    Amir Mukhtar Ashrafi

  16. Salim Khan

    January 29, 2015 at 9:14 pm

    How do you test Magnetron?

  17. Nwosu Anthony

    January 30, 2015 at 12:16 am

    Thanks alot for the article its very helpful

  18. james

    April 27, 2015 at 1:38 pm

    I like whati read and learn about microwave repair iam still new inchield and need some help with a microwave a custermer boiled eggs in her microwave and tald me the microwave make an exploiding sound and it is dead no power when i open the microwave found the fuse had pop the door swithses fualty it still dont want to come on removed the fuse and put a 100watt bulp aa rplacement fr the fuse put it on no power when i remove blue or black wire from transformer it will come on but still no heat please i need advice


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