A Microwave Oven With Many Faults Repaired
A friend of mine brought a microwave oven for repair and explained that the moment he plugs in the device even when the door of the microwave oven is open, the earth leakage button trips.
If you look inside the microwave oven you would see that it was clean and nice.
There was neither dust nor any humidity signs and I was wondering why this is happening?
Usually when this happens I do directly to the safety micro switches and check there for faulty parts but in this case it was not that kind of fault.
I connected my multi meter probes on the main power of the transformer and plugged in for power, I got 220 AC volts here but in few seconds the reading was lost and the earth leakage tripped again.
I traced the issue from the main two pins of the power transformer back to the power panel on the front of the device. I took the board out and started checking any shorts there but I could not find any.
The only thing I could find was cold soldering joints on the legs of the 220/10 AC volt transformer on that board. I re soldered all these cold joints, put everything back and powered on the device.
This time, the microwave oven stayed on and the earth leakage did not trip but when I tried to heat up something, the counter was running but the device was not heating up the water I put inside the device.
I checked for 220 going to the microwave front panel and I was getting 220 AC volts there but the question here why it was not heating the water up?
When I checked almost everything on the microwave oven, I came across this. The door was not sitting up right to trigger the micro switches inside the device. When the device powered up and I press down on this door, the microwave oven started to heat up things and when I let go, the counter on the front panel keeps running but no heat is being produced.
These are the screws that hold up the front door; one of the screws was loose. When I tied up the screw, the door was sitting the way it should.
I powered on the microwave oven after I did the door adjustment and everything worked according to specs. It was heating the way it was supposed to.
Mission Accomplished.
This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.
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Note: You can check his previous repair articles in the link below:
https://jestineyong.com/iphone-11-pro-broken-screen-replacement/
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Parasuraman S
January 4, 2021 at 6:46 pm
That was a special wave of problems and you could solve all quickly and vow, the microwave is back to life! Many thanks for this article containing new problems and solutions!
Andrew F. Ali
January 4, 2021 at 10:54 pm
Well done!!!
Waleed Rishmawi
January 5, 2021 at 9:20 pm
Andrew: thanks man. have a good day
Waleed Rishmawi
January 5, 2021 at 9:19 pm
Parasuraman: the repair was not solve quickly it took me a while to figure out the misalignment of the door but finally it was repaired adding more experience to me. have a good day
Albert van Bemmelen
January 4, 2021 at 7:37 pm
Good repair with many faults fixed but in which no defect parts were found. Which is quite surprising just as the tripping of the earth leakage button the moment the device was plugged in even when the door of the microwave oven was open. Which could have been a safety issue.
Waleed Rishmawi
January 5, 2021 at 9:21 pm
Albert: yes no parts were found faulty but alignment of the door and therefore effecting the relays inside the device but finally it was fixed and maintained. have a good day
Yogesh Panchal
January 4, 2021 at 10:58 pm
Waleed,
Dry Solder and loose connection is always danger.I know one day while using hot water geyser i smell some thing burning and on checked i found mains cord of geyser is getting hot and my house mains line tripper is tripped.i just switched off the geyser on tracing the cause i found mains plug of the geyser is loose contact in the socket and result of that due to over heating causing the short.However i removed the geyser and disassembled for finding the cause but did not find any obstructor.I replaced mains socket and plug.......still it works fine.
Waleed Rishmawi
January 5, 2021 at 9:23 pm
Yogesh: totally agree especially in microwave ovens it keeps tripping the earth leakage and causing alot of headache. I am glad you were able to fixed the problem at your house. have a good day
Henrique J. G. Ulbrich
January 5, 2021 at 2:07 am
Well done, Waleed. Thanks for sharing. I´ve found two strange facts. The first is due to earth leakage tripping. This only occurs if there is a current leakage between a voltage wire and the metallic part of the device body (being the device due grounded by the PE connection, which not always happen). Dry solder points reworked as you explained just restore the connection, nothing to do with leakage to earth. It is not a reason do the earth leakage switch to trip.
The second strange thing is that, if you had measured 220 V on the transformer wiring input, so the microswitches were all drove correctly. If there is a misadjustment in the door that causes a microswitch to not operate, so you couldn´t have 220 V at this point as measured.
Waleed Rishmawi
January 5, 2021 at 9:29 pm
Henrique: you are most welcome.
dry soldering helped preventing the earth leakage tripping due to the fact it was sparking but the main fault was the misalignment of the door and the relays inside the device which i believe it was the main cause for that
have a good day