Modification Of Microwave Oven
This sharp microwave oven was brought to me by a woman in the neighbourhood with complaints not powering ON. This microwave was once repaired by me three years ago. If you missed the acticle you can still read it at article 988 of 17/11/22.
When I removed the sheet cover and scrutinised the components,I did observe a/c input fuse has blown, before replacing it, I tested all other components: door switches, thermal switches, high voltage components, etc…all tested good. So what I decided to do next is to remove the two high transformer a/c input pins and replace burnt fuse,why do I have to do this…… this’s how to test the main control board, if turntable works(roll) a/c bulb On, and fan turns, then board is good,including door switches, but in this case nothing happen: microwave still dead….this is a sigh of bad control board. So I pulled out the board for diagnosis, check all components on board….all tested good,there is a spider legs ic on it which can’t be tested, so suspected it to be the problem.
So I decided to check for a replacement,which I was not able to get in the local market, so a friend of mine who repairs only microwave oven in the city repair village told me he can modify it to manual type.
So I handed it to him to do and left his place, some minutes later I went back to him and alas he had finished modifications without the H/transformer,for I removed it before taking it to him,but when the device was test, without transformer, turntable,fan and bulb work, so took it to my workshop, removed the sheet cover once again and examined the wiring, did a wiring diagram,documented it for my future use.
Then fixed the h/transformer and all other high voltage components and switch ON, to my surprise the a/c input fuse got burned again which I was not expecting, for I have tested all and all pass tests.
So I call the modifier on phone, inform him about this new development,he told me the high voltage capacitor must be bad,which I find it difficult to accept because I tested it on multimeter: use of 200ohms and 2000ohms. But I was suspecting transformer, while trying to remove transformer,I accidentally broke one of magnetron input pins….another problem so to say.
So change my mind,forget about removing transformer,fix a working old spare magnetron that I have, replaced a/c input fuse again, and replaced the h/capacitor and switch ON….Wow microwave came alive and water in a cup got heated.
However,the problem of broken magnetron pin became an issue, I understand the magnetron socket can be replaced, so I embark on repairing that too.
I eventually replace the magnetron socket and fix it to the microwave oven and it worked well.
The repair experience of this will probably be shared latter on another article.
This is the finished repair work.
This article was prepared for you by Imoudu Onwumah from Nigeria. He is 62 years old and has just 3 years experience in electronics repairs. I started career in hotel industry as a chef, but then I was doing repairs only in electrical repairs as a hobbyist. In 2018, I decided to learn about electronics which through Jestine’s electronics e-books and holding my hand, am an electronics techie today.
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Note: You can read his previous article on Blue Ring Tester Goes Packing Up
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Albert van Bemmelen
December 28, 2025 at 6:34 pm
Using the microwave oven without the Sharp control board probably meant using the oven without power control or some other function. Like no working beeper function. But if even after modification without that board the blown fuse was caused by the bad HV capacitor, it probably also meant that the control board was still fine? Sadly you didn't share the drawing mentioned. Your previous repair on this oven as article 988 of date 17/11/22 sadly didn't show anything.
ANTHONY PATERSON
December 28, 2025 at 7:42 pm
Initially, I was unsure what changes had taken place but then realised the electronic touch-controls on the bottom of the microwave control panel had become defunct and that a manual switch/timer had been installed to replace them. If my understanding is incorrect then accept my apologies.
Parasuraman S
December 28, 2025 at 8:18 pm
Vow! That was a marvelous job done, dear Imoudu! Eagerly look forward to seeing your article on fixing the broken pin!
Mark J
December 29, 2025 at 1:04 am
Imoudu well done on the repair...
Imoudu.O
December 29, 2025 at 5:12 am
Anthony.P
I guess your understanding is right,thanks friend
Imoud.O
December 29, 2025 at 5:14 am
Anthony.P
I guess your understanding is right,thanks friend.
Imoudu.O
December 29, 2025 at 5:17 am
Parasuraman.S
Thanks sir, I will surely do that.
Yogesh Panchal
December 30, 2025 at 6:02 pm
Good Job!Imoudu,
Capacitors are unpredictable while testing, Better to try using some working one.
Philip
January 3, 2026 at 11:41 pm
It remains unclear to me what modification was done by the other technician shortly after you had shown him your back. But if the specialists' modification involves bypassing the spider resembling IC, then the magnetron may soon face execution due to improperly metered voltage and current. Well, thats only if there is no other IC that oversees current and voltage metering to the magnetron. In my view, I stand corrected though, possibly getting the spider IC out of the control way may lay off the thermal switch and alarm beside other important functional systems that the spider IC controls. The angular view of the taken photos only shows a few primary circuit components. So I cant say with certainty that the magnetron will soon face the hangmans noose because there could be a control IC thats out of visibility. If the unseen IC controls power to the magnetron without being influenced by the spider IC, then I can imagine that the microoven will see many days and nights of the magnetrons' heating loyalty.