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A Dead Universal Microwave Oven Repaired. Model: Uni. 2040

By Jestine Yong on September 12, 2013

The microwave oven was brought to my shop for repair and the complaint was it does not heat. While the customer waits, I powered up the machine and tried to heat up some water in a glass, it did not heat. Based on this information, I opened the oven and started working on it.

When I checked for any volt reading at the main transformer, there was none. I went back to the main fuse and checked it out, the fuse was open. The main problem with this microwave oven was not heat problem, it was power problem.

I put a 100 watt light bulb across the fuse terminals and powered up the oven. The light bulb was on but very bright indicating a short in the oven. That explained why there was no heating going on and why the fuse was open.

I disconnected the two wires from the main transformer and powered up the machine. The light bulb was on but not very bright indicating that the short was gone in the oven. When I checked the voltage reading there, it was only 180 volts. It was supposed to get 220 volts at the connectors of the main transformer. That triggered my thoughts to started checking the lines that were feeding power to this transformer.

As you can see in the photo above, these black parts are safety switches that trigger the power to the transformer once the door of the microwave oven was shut. That was my next move to check these safety switches. I found one of the switches shorted and that what was causing the short in this microwave oven.

I found a replacement for this switch in my shop. The moment I replaced it and did the volt testing, I got 220 volts at the terminals of the power transformer. I kept the light bulb connected till I made sure that there was no short left in the microwave oven. Once I replaced the light bulb with 8 amps fuse, I powered up the machine and heated some water in a glass. It was hot and nice.

Customer might miss led us about certain problem that is why we as technicians, we need to do our own testing to figure out the problem. 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. Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.

By the way if you have any good repair article that you want me to publish in this blog please do contact me HERE.

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microwave oven repair

6 Comments

Amir Mukhtar

September 13, 2013 at 3:40 am

Sir, Jestine
thanks you for sharing a nice article on microwave oven.
thanks also to Mr. Waleed Rishmavi.

yours Student
Amir Mukhtar Ashrafi

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Waleed Rishmawi

September 13, 2013 at 4:02 pm

you are welcome Amir.

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Robert Calk

September 14, 2013 at 8:16 pm

Thanks for sharing the article with us Waleed.

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Waleed Rishmawi

September 15, 2013 at 5:02 am

Robert: you are welcome.

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raymundo saura

September 17, 2013 at 10:02 am

thanks for sharing GOD bless

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corriete

January 28, 2015 at 5:55 am

thanks sir for this piece of info.YES you are right. the customer can mislead us so all times we have to test. great job

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