Dead Fuse, High Voltage Diode and Capacitor Found In Microwave Oven
This Microwave oven was brought for repair and the main complaint was, it went dead while trying to heat up something. As the customer explained the situation and at the same time he told me that this device is urgently needed.
As you all know how much I hate the LG products but because the customer is also a friend of mine, I was willing to help out. So, here it goes.
the first thing I did when taking the cover off, is to discharge the main capacitor and I did that by touching the two terminals of the capacitor with two screw drivers with their handles insulated. Shockingly, the main capacitor was completely discharged already. Usually I get a little zap but this time, it was dead.
The 12 amp fuse on this device was already open and it had to be replaced. Before I replaced the fuse, I did some checking.
First thing I tested was the magnetron and I did that by setting the multi meter to ohm setting and checking the resistance between its terminals and its body and I should get no reading. If I get any reading, the magnetron is defective and it had to be replaced. It checked out fine
The second part for testing was the main diode which is called the bleeder. It is usually connected to the main capacitors. When checking this diode, I was suppose to get no reading on it both ways but when I checked, I got reading on both sides and this is a clear indication that it is faulty.
From experience, if this was shorted, I also check and replace the main capacitor even if it was giving me a good reading.
When I checked it with my multi meter, the reading was way below the 1.05 UF and therefore had to be replaced.
This is the capacitor replacement. It was a little bit higher in rating but it should work fine.
So far, I have replaced the diode, the capacitor and the main fuse. It was time to power on the microwave oven and hope for the best.
I put the cover back and powered up the microwave. I put a cup full of water inside and started the microwave oven and as expected, it was working the way it should be.
The microwave oven did not go into shut down, the water got hot and the customer was happy, what more can I ask for.
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.
P.S- Do you know of any your friends who would benefit from this content that you are reading now? If so, forward this website to your friends or you can invite your friends to subscribe to my newsletter for free in this Link.
Note: You can check his previous repair articles in the link below:
https://www.electronicsrepairfaq.com/igbt-transistor-shorted-in-welding-machine
About admin
Jestine Yong works as an Electronics Repair Lecturer in Kuala Lumpur Malaysia and his training website is http://www.NoahtechElectronicsTraining.com. You can check out his repair blog at http://www.JestineYong.com
21 comments on “Dead Fuse, High Voltage Diode and Capacitor Found In Microwave Oven”
Leave a Reply
Leave a Reply
This site uses Akismet to reduce spam. Learn how your comment data is processed.
Very well explained repair. High power devices, no matter what defects they might have are safe in your capable hands. Welders, Microwave ovens or any device we can think of are fixed in notime! I only wonder why you dislike LG that much?
Albert: thank you very much my friend. the reason I do not like LG is because they are excellent made once they are running but when they break, the parts only found at LG centers and they are usually expensive. my aim at the shop is to reduce prices as much as possible but when LG put their prices up like that, that aim is not accomplished. have a blessed day my friend.
Waleed thank you. As I write I have my magnetron on the table. I put the meter on the ohm scale (200) and I get a reading between its terminals and when I put between each terminal and body, I do not get any reading. I also tried the diode continuity test, and I heard a bip sound.
Could you say the magnetron is defective?
Hi All this information is very useful Thanx
Rodney: I am glad you liked it. have a blessed day
After reading your article, the question that came to my mind was why you disliked LG so much. But you’ve already answered that for Albert.
I thought diodes are supposed to show a low ohms reading on one way and high (infinity) on the other. But here you said that you shouldn’t get any reading from either way. It’s just a bit confusing. Can you explain to me why that’s so?
I’m an electrician, but I’m trying very hard to get into electronics repair because it’s interest that I had from childhood.
Hi Gashaan. Because it is a special High Voltage Diode it acts differently, not exactly like any normal silicium diode. By-the-way: I also was an electrician in the beginning +40 years ago but never liked that job. For me it always was electronics.
Albert: thank for explaining the High voltage diode. I appreciate it very much and have a blessed day
Quite unusually, I book marked this link for future reference, because the contents and information shared were really rich in its value, especially when I have one LG microwave oven waiting for its turn! Many thanks!
Parasurman: I thank you for your nice comments. good luck on the repair of the LG microwave oven. have a blessed day
Good, Waleed. Indeed an efficient maintenance. Thanks for sharing. Just a doubt: the bleeder function in microwave ovens does not reside on the diode. This function is performed by the capacitor, that has a resistor in parallel (as can be seen in two pictures of your article).
Great job. However, I must comment that I have fixed countless microwave ovens that had defective high voltage diodes and not once did I changed the high voltage capacitors. You are correct respecting the testing of the diode. There are special meters for testing those diodes. The meters used by us can only be used to determine if the diode is shorting and or has become short circuited. When testing a diode, if there is no reading, it could be an indication that the diode has become open circuited. To determine if the diode is open, you can connect it in series with a light bulb, if the bulb does not light up, the diode is open.
Devon: thank you very much. i never used this method of light bulb to test a bleeder diode in a microwave oven. I will test it out. thanks for the input
In addition to the reasons given heretofore, another reason for not liking LG products is often times they will not sell you the parts unless you are one of their authorized service representative. I feel the same way about Sony products.
Devon: yes that is so true. And if you want to buy the parts anyway and do it yourself it will cost you and arm and a leg for it. I ever had the same issue with Sony Product. thanks for your input. have a blessed day
Thanks much for your technical work sir
Paul: you are most welcome. have a blessed day
Good job Waleed
Jai: thank and have a blessed day
Hi Waleed.
Thanks for the repair article.
Just one thing I would like to point out.
You said that the diode is also called the “bleeder”.
I dont agree. It is a rectifier.
The bleeder is a resistor which is found inside the capacitor.Your photos show 10 meg ohm quite clearly.
Thank you very much for repairing dead microwave oven. And i want to use that procidure to repair my in-law’s microwave oven. It comes on but the programming buttons are dead.