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BackLight Problem In LED TV Repaired

By Jestine Yong on November 18, 2023

A regular customer who is a cctv technician called me on phone to meet him at his client house, on which getting there, this 43″ combo led tv was shown to me with complaint of no picture, but there is audio. When i flash my flash torch light on the screen i could see traces of faint images which indicates it’s backlight problem.

So i carried tv to workshop, removed back case of tv and on visual checks, i noticed e- caps on backlight circuit had bulged. (Let me point out here the brightness of backlight had been defaulted to 50% by the manufacturer.)Moreover when i checked the backlight voltage from connector pins, it reads just 15V.

The bad e- caps values are 220uf/50v ×2, 470uf/16v, however i don’t have 220uf/50v in stock, so i had to use 220uf/35.

But before i use this, i did measure the voltage across the positive pin of cap on board which was 30V, so i did assume 220uf/35 should be able to work for it….I stand to be corrected guys.

After replacing bad caps and powered tv, it came on beautifully, picture below. This’s the finished repaired 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 Dead Microwave Oven Restored

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LED TV Repair

12 Comments

Anwar Shiekh

November 18, 2023 at 7:00 am

Capacitor repairs are the best.

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LUIS GALANG VILLEZA

November 18, 2023 at 7:05 am

Most of problem often cause by bad capacitors

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Parasuraman S

November 18, 2023 at 11:11 am

The voltage of a capacitor should at least be double if not treble, which is what most of the experts recommend. Otherwise, it won't last long and fail again. Good work, though, and many thanks for sharing!

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Tito Kanshulu

November 18, 2023 at 1:48 pm

Good repair Sir, but replacing with e-caps 35v was a bad idea. The customer will in the next few days come again with the same complaint. Try to find e-caps of value 330uf 35v not 220uf 35v. 220uf 35v will not stand the heat. It will soon fail.

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Albert van Bemmelen

November 18, 2023 at 3:31 pm

I always call myself lucky when it are just bad e-caps. And by replacing them is the fastest way to know if everything else afterwards works as they should.

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Imoudu.O

November 18, 2023 at 9:36 pm

Tito.K and Parasuraman.S
Thanks for your corrections which are highly appreciated and noted. Learning is endless in mans life. I keep on learning from you good guys

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Imoudu.O

November 18, 2023 at 9:38 pm

Luis
Thanks for your comment,have a nice day

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Imoudu.O

November 19, 2023 at 4:17 am

Albert.B
Yes you are right.

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Menahem Yachad

November 19, 2023 at 5:33 pm

There appears to be a lot of misunderstanding about Capacitor voltages and performance here.

If you are using good-quality GENUINE 105°C caps from Panasonic, Nichicon or Chemicon, then 20-30% margin above the actual circuit voltage is just fine.

If you are using DingDong or WingTang 85°C caps from China, then perhaps even 10x the voltage rating may not be sufficient.

The reason WHY you should not have a high voltage rating is because the capacitor may never be able to fully energize when the actual circuit voltage is far below the cap's voltage rating, causing unstable current (not voltage) in the circuit.

Regarding HEAT - a cap's voltage rating will not greatly influence how much the cap will heat up. What really influences how much the cap will heat up, is its RIPPLE CURRENT rating, versus the circuit's ACTUAL ripple current.

And being that many Chinese manufacturers publish very unreliable datasheets, we can understand WHY these Chinese caps heat up and fail much more than Panasonic or Nichicon caps. Their poor quality-control during manufacture simply does not correspond to the numbers published in the datasheets.

Menahem Yachad
CondorAudio
Jerusalem

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Waleed Rishmawi

November 20, 2023 at 3:36 pm

good repair although I do not agree with the lower voltage capacitor replacement..that is not a good idea to do that. thanks for sharing and have a blessed day

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Yogesh Panchal

November 20, 2023 at 11:05 pm

Good Job! Imoudu.O

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Humphrey Mndaka

November 22, 2023 at 3:59 am

Thanks my friend for sharing this, this is a Common problems with cheap tv from China which has unfortunately flooded the Kenya Market, Seems like Nigeria is not left out...Whenever i get such a case i usually retain the same capacitor-capacitance but voltage rating i move higher...in your case i see the same problem coming up again in a few weeks time....i am not a prophet though, hahaha

Regards Humphrey

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