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Panasonic Microwave Oven Operates Thanks To Recycling

By on March 30, 2015
microwaveoven repairing









I have never worked on a microwave oven before. In fact I had no idea how they worked. So when a friend bought his in for repair, I realised that it was time for me to do some research. I was surprised by their simple design.

Microwave ovens operate due to 2 main components – the transformer and magnetron. The transformer outputs a high voltage of about 4 kV. The magnetron uses a form of vacuum tube. By applying a high voltage at the centre filament, electrons are ‘boiled off’ this filament and fly to the circular copper anode cylinder. Two magnets are fitted at either side of the centre filament and these are used to ‘bend’ the electron path back toward the centre filament. The magnetic strength is adjusted to get these electrons to just brush past the vane openings. This in turn creates an oscillating wave – the microwave radiation used to heat the food.

microwaveoven repair


The microwave oven was invented by Percy Spencer. In 1939, while working for the Raytheon company, producing magnetrons for use in radars, he noticed that a chocolate bar had melted in his pocket while he was standing near an active radar. He purposely tried to heat a corn kernel and popcorn was created. By enclosing a magnetron in an enclosed metal box, the electrons became concentrated. Raytheon filed for a patent in 1945 and the first commercial microwave oven named the ‘Radarange’ (weighing 750 lbs, 6 feet tall and costing $5000) became available.

As my friend bought in his microwave, he passed by mine and discovered that they were identical! At least I would be able to do some reference testing if required. I just had to make sure that my wife didn’t know what I was up to!!

This microwave operated, had a light and also circulated the plate. The main complaint was that there was no heating. I confirmed this with a glass of water. After removing the cover I was able to divide up the circuits. After testing the transformer, my next step was the magnetron. More Research!!

They seem very simple, but how do you test them? I found an internet site that gave me a few clues about how to test it.

In the meantime, I had to make a trip the recycling depot. They allowed me to bring some items home, which included (believe it or not) an identical microwave oven to both mine and the one I was working on!

Here is how I tested the oven from the recycling depot and then compared it to the inoperable one. I was unsure about the safety of this test, but by putting any metal in water, the energy is dispersed into the water and will not bounce off the metal. Just to be sure, I carried out this testing outside and also while my wife wasn’t home!


See the photos below:

microwaveoven repaired



You may also click on this link to watch the video.

Notice the light flashes off and on as the electric and magnetic fields change rapidly. This test proved that the recycled oven operated correctly. Further testing proved this to be the case. Why do people throw out perfectly good items? We live in a throw-away society. Frustrating!! I’m sure you would all agree.

I further pulled down the faulty microwave and noticed several things. The plastic cover that holds the light bulb in place was melted and also there were slight burn marks on the magnetron cooling fins.

microwaveoven repairs

I also noticed that one of the magnets was cracked and apparently this is a common fault with magnetrons.

I priced a new magnetron and the customer decided that he would get a new microwave oven. But now that I had a recycled part, he was happy to have the item back at a cheaper price.

Replacing the magnetron took only a short period of time and after doing so, I carried out further testing to prove the repair. The customer was happy to have the oven back up and running.

We can do so much with recycled parts and give electronic items a new lease on life.

Warning: Never work on the secondary side of the transformer without first making sure the high voltage capacitor is completely discharged. All high voltage capacitors on microwaves have got an in built discharge resistor but if the resistor goes open circuit then the capacitor will stay charged. For your information it is the amps that kill not volts, these caps in microwave can kill so beware.

You may also watch the video below on how to troubleshoot Microwaves Oven In Minutes:

This article was prepared for you by Mark Rabone from Australia.

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  1. Andrew F. Ali

    March 30, 2015 at 9:19 pm

    Very interesting!! I usually test microwave ovens by using a glass of water only. Now I will try this new method of testing with the light bulb in the water...Very nice indeed.


    March 30, 2015 at 9:43 pm

    Hi mark,
    It was a good repair job done with caution,Keep good work.Lot of thanks for sharing the knowledge.

  3. Humberto

    March 30, 2015 at 9:55 pm

    Hi Mark Rabone, I like saving devices from the dump too. By the way, could you give the website you found a few clues about how to test the magnetron.

    • Mark

      March 31, 2015 at 6:16 am

      Hey Humberto,
      Try as I may, I can't find the site that suggested to use a globe in water! It seems very safe and I would be confident doing it with my own microwave oven for a short period of time (I used 10 seconds) - as long as my wife wasn't home!
      Other sites that were of use were:
      E10-2010-06 - Panasonic

      I hope these may be of some use to you.


    • Mark

      April 1, 2015 at 6:44 am

      Hey Humberto,

      I finally found the site that suggested to use a light bulb to test the operation of a microwave. While I wouldn't suggest you do any of the other experiments listed later on in the article, I felt very confident using a light bulb in water & it directed me to a successful diagnosis.

      I hope this helps


  4. sudhir dullip

    March 30, 2015 at 11:17 pm

    Hello yestine
    It a very nice method of testing the magnetron of microwave.
    Before i test with a glass of water ;i will surely test as mention.
    Thanks yestine.

  5. Yogesh Panchal

    March 30, 2015 at 11:25 pm

    Good experiment Mr.Mark,

    It is very dangerous to do such an experiment when you are alone at home at least some body have to be there to provide us help in an emergency. any way just keep up sharing your experiments!! yes obvious with "CARE"

  6. Barry Merridan

    March 30, 2015 at 11:41 pm

    Hi, I used to repair microwaves for a living, and I am just a bit concerned that you never mentioned the safety aspect of a microwave oven before taking it apart. The obvious is to remove the plug first, secondly the capacitor should be shorted out incase it's still holding a charge. We had 3 engineers killed while working on a live microwave so I think it is important to advise this. Microwaves can easily blow a fuse inside, as customers remove an item then flick the door shut with their elbow, there are 5 micro switches connected to the door and all must close in a set sequence, should the door be closed too quickly it will blow the internal fuse.
    The main point on this is safety first, please make sure the capacitor is drained before starting work.
    Many Thanks

    • Mark

      April 1, 2015 at 6:29 am

      Hey Barry,

      Thanks for your comments. You are correct in saying that I should have stressed the safety aspect of the repair. I guess some of the things we do without thinking should be mentioned for the benefit of others. If I need to work on an appliance without live measurements, I remove the plug and have it in front of me so that I can physically see it, being confident that I have removed it. Any live testing is done with extreme caution as we can become a bit lazy and forget about the dangers of high voltage.
      While I was doing some research on microwave repair, one site said to discharge the main capacitor with a screwdriver! As you can imagine, some of the comments were very direct! ALWAYS discharge the capacitor with a load of some sort. I have made up a series of resistors on a pair of plastic tweezers that does the job very safely and I always check with a voltmeter afterward to confirm that the voltage is at 0.
      Once again, thanks for your reminders about the dangers of high voltage.


  7. sam montero

    March 30, 2015 at 11:44 pm

    Hi Mark
    From the oven I get for repair, the xformer
    output is 2Kv. The voltage is doubled to dc4Kv
    for the magnetron to operate. Usually a diagram of the circuit is pasted on the cover.
    I was able to get voltage readings from old sears roebuck mw oven. Hope this could help.


  8. Waleed Rishmawi

    March 31, 2015 at 12:18 am

    another way of testing magnetron is by measuring resistance between the body of the magnetron and the the two pins..there should be no readings there. when doing the same test with the two pins of the Magnetron, there should be reading of a continuity results.
    in other cases, no heating cases can be solved by checking the fuse between the main capacitor and the transformer. there is a fuse there that goes up to 5kV rating/.7 amp. most of the time that fused would be blown and that causes the magnetron not to get any power there causing the no heat problem.

    • Mark

      April 1, 2015 at 6:50 am

      Hey Waleed,

      You are correct in saying to check for continuity in the filter and filament of the magnetron, however in my case, the resistance tests were correct and it was due to damaged magnets that resulted in the magnetron failure. You can see this in one of the red circles shown on the photo above.

      Thanks for your comments.


  9. Robert Calk

    March 31, 2015 at 1:21 am

    Thanks Mark. Good job on all counts! I glossed over info about microwave ovens but not in depth, I guess because I haven't worked on one yet. Thanks for the article and tips.
    Percy probably realized that if a chocolate bar was melting in his pocket, he himself was being slowly cooked also.

  10. moshe

    March 31, 2015 at 3:58 am

    thanks for sharing a job well done & informative.

  11. Luis Estrada

    March 31, 2015 at 8:55 am

    Mark, nice troubleshooting and write up. However, what were you hinting at when you said 'the plastic cover that holds the light bulb in place was melted'? We have an oven that its light bulb burns up in months of normal use. Keep up the good work.

    • Mark

      April 1, 2015 at 6:34 am

      Hey Luis,

      The plastic cover was melted not by the excessive heat from the globe, but rather from the failing magnetron. In one of the pictures above shows a red circle where there was discolouration of the magnetron from excessive heat and this is where the plastic cover had melted.

      Thanks for your comments


  12. Anthony

    March 31, 2015 at 3:36 pm

    Great work Mark and thanks for would seem these things are pretty robust and hardly ever breakdown apart from perhaps the touch pads that control the functions .


  13. Robert Francis Gomes

    March 31, 2015 at 3:45 pm

    Thanks for the information. It help us also. I also have a microwave oven which is creating problem when used for a long time, it shuts down and after it get cool down its start work again. can you put some light on it.

    • Robert McVay

      March 31, 2015 at 11:58 pm

      ...most of these have a bi-metallic thermal cutoff switches attached to the heatsink or case of the magnetron cavity. They are similar in shape to a T0-3 power transistor case with 2 screws). They usually are high current devices 120-240VAC at 10-20Amps and are a critical safety device over heating feature.

      They are normally always in the ON state until a specific over-temperature condition is reached at which point the bi-metallic strip inside seperates and breaks the contacts resulting in safety 'cutoff' (stopping current from flowing through the device).
      Most are self resetting (once the temperature goes down they reset back to ON state in 5-10 minutes).
      Occassionally they go bad.
      a)may start to trip at the wrong temperature or trip intermittantly.
      b)main contacts may become arc-welded and melted off resulting in no current flowing through them under any conditions.

      replace with one of the same rating and physical footprint observing correct wiring and heatsinking as the original part.
      Remember to also check any fan or impeller (fan blade) for correct cooling operation. Make sure all ventillation slots in the case itself are free of dust, fuzz and debris.

  14. Zed Pato

    March 31, 2015 at 5:57 pm

    nice job mark and thanks for sharing this microwave repair.

  15. Andre Gopee

    April 1, 2015 at 8:56 am

    Good Work Mark, I learn something today about Microwaves. Very Interesting and keep up the good work.

  16. n. alex

    April 1, 2015 at 10:47 am

    very interesting! thanks for sharing the info. cheers!

  17. frikkie

    April 1, 2015 at 4:40 pm

    I used to work for a guy repairing electronic equipment including microwaves. Just something I also want to mention.The magnetrons become very hot as well.So one must keep in mind to check that the cooling fan sucks out the warm air and blows it out at the rear of the microwave.If the fan doesn't work,the magnetron will overheat causing the magnets to crack also.The magnets helps to focus the radiation beam.

    • weyi Nasser mohamed

      April 2, 2015 at 6:49 pm

      good te aching about microwave repair,well understood thanks.however can you help direct me on how to fix my iphone 3. it only dis plays apple brand sign,but while charging does not open .and when the charger is removed it switches off.

      • Robert Calk

        April 3, 2015 at 12:36 am

        Have you tried replacing the battery?

    • Mark

      April 4, 2015 at 7:59 am

      Hey Frikkie,

      Thanks for your comment. I honestly didn't think about the fan (although this one was working well). I guess it makes sense that the magnetron needs to dissipate the heat produced.

      I have learned a lot from both the research that I did during the repair and also all the comments that have been provided on Jestine's site.

      Thanks again

  18. Rashwan Shaban

    April 29, 2015 at 5:30 pm

    Good job man, In fact I learned a new things from you.
    Thank you.

  19. cliff louis

    July 10, 2015 at 3:26 am

    thanks for U R INFO i enjoyed waching learning from u
    man good job

  20. joshwa mukunzi nasio

    July 30, 2017 at 4:42 am

    Good job engineer


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