LED Backlight Problem In LG TV- Checked With LED TV Backlight Tester
A couple of months ago a friend asked me to help him fixing his second time defect Samsung backlight tv problem. The first time his Samsung was still fixed in Warranty time. The tv was a Samsung European model UE39F5000 or a similar model slightly bigger in that series.
I already had ordered Samsung type 2828/3228/1,5-3Watt backlight leds with internal zener diodes. (3,13 Euro for 100 leds). And those worked also perfectly when tested on my Led backlight tester. Which made testing tv led strips a real easy fun thing. Something that is difficult to do with just your digital meter at diode/beep test. Testing one led is no problem but only if the copper tracks on the strips are visible. But most strips only can be tested at the beginning of the strips where the copper + and – contacts are free. And that can’t be done with the low voltage of your DMM.
Lateron I also had ordered other more expensive high power type 1 Watt 3537 Samsung backlight leds. (they were 5,80 Euro for 50 leds). But strange thing was that they seemed to easily short circuit on the >322V DC test voltage coming from my tester. They immediately dimmed into giving no light whatsoever with only showing 0V on the Led tester’s display. But after I tested those same leds afterwards on a voltage of 3V they were just working fine! So they internally must be heavily protected against any high overvoltage to save them from fast destruction.
But fixing the backlight of that Samsung tv was put on hold for a later time because my 3 replaced type 2828/3228 leds worked fine on one of his led strips but his original 5 leds on that strip afterwards for no known reason simply had quit working. We had no clue what had happened. And all his led strips had also two zenerdiodes 12V and 24V on the voltage input of which a couple of them were completely blackened after they had collapsed. Something that you do not see anymore on newer tv’s.
So when my good friend Chafik recently asked, already months later, to help him fix the backlight of a larger LG 47LA6208 tv, I had my doubts. Next photos show the Led tester I use and the label of the 47 inch LG tv.
Although it was quite easy to disassemble the LG to reach the partly defect strips with 6 x 9 leds, we first do have to remove a lot of screws on the outside. But it really may be a two person’s job to prevent breaking the large 47 inch thin glass screen when you want to turn open the screen from the led back panel. Best way is to turn the screen with the glass plate downwards on a big table. Leave the glass plate on the table and then remove the back away with the led panel in it .
And next place the metal backside downwards on the table with the leds inside facing upwards and carefully remove the light filters without getting them dirty onto the glass plate. We therefore first removed the two outside rectangular plastic and the aluminium strips that normally hold plates and screen together. Which we have to remove In order to free the inside metal back panel with the led strips we need to check. We accordingly test each strip with our led tester for bad leds. And if necessary by completely removing bad strips to be able to replace any defect leds with our hot air solder station as was shown on previous photo.
The biggest handicap of fixing the led strips on this LG is here that the strips are made from 2 layer copper strips. Which makes it almost impossible to use the easy 260 degrees Celsius hotplate method. Because the copper makes it almost impossible to provide enough heat this way to reach the solder of the leds on the top layer. That is why we have to use a hot air solder-/desolder station.
We set it to about 290 degrees Celsius which took at least about 30 seconds for the top copper layer to reach the right temperature to be able to remove the bad leds. And we used the same temperature to place leds back with sometimes the help of our solder iron if it was necessary to clean the solder on the copper tracks, or if it helped to better place the new leds.
This can be done by one person but we did the job together. One person held the air gun while the other removed the bad leds from their position on the strips.
Naturally we also need to remove the lenses first, and we have to glue them back on after those bad leds were replaced. Of course we also can just replace all strips by ordering new strips but the repair will cost much more afterwards. 60 Euro for 6 led strips with 9 leds on them is the high price we about have to pay for the complete set for this LG. However that way we can rule out that leds, like after led repair, differ in age and lifespan. Anyhow, replacing leds one by one manually is much
cheaper. Next photos show the tv with the progressing repair of the backlight panel. First photo shows all leds are working perfectly!
Because we use leds that were not specifically for this LG, the solder pads on the leds differed from the copper pads on the strips and we had to shift the new leds a few millimeters to make them work.
I am happy that after our work all leds worked! But look closer and you’ll probably notice that one of the lenses is missing. After we took the photo the plastic lens was glued back on. Gluing sometimes simply appears to be more difficult than soldering. If I would have to give this photo a title it could be “Led’s work” which I believe almost resembles another famous title of a song from The Stones and Mr.Bowie which was “Let’s Work”. But it also could be that I become a bit senile at my age (LOL).
Anyway, we are ready to assemble everything back and closed the tv. The last photos show the great result after we connected the HDMi input connector to the output of our laptop.
Let’s hope that all backlight leds will survive for a very long time after our repair!
Maybe in the near future fixing and replacing these backlight leds will be less time consuming. Repair wise we may have to admit that those old long lasting HV CFL tubes were not so bad in the recent past as we probably were thinking?
The older led tester I used in this repair in the meantime now also can also be bought with an extra switch to select the led current. I have no idea if you would need that but since that led tester is furthermore identical and just as expensive as the meter without the extra switch, I now would go for the newer model. Anyway, my young friend Chafik can be proud with the repair job done at his ICT shop.
Until another repair!
Albert van Bemmelen, Weert, The Netherlands.
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Note: You can read his previous repair article in the below link:
https://jestineyong.com/heater-element-problem-in-s993a-vacuum-desoldering-gun/
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Suranga Electronics
October 3, 2018 at 1:14 pm
Hello Mr,Albert van.
Good Job !
Common Fault Some LG TV Model
BackLight Problem.
Albert van Bemmelen
October 3, 2018 at 5:43 pm
You are completely right Mr. Suranga! Most tv´s nowadays suffer from backlight problems to happen, including this LG. That is why I think those old cfl backlight tubes were a lot more reliable over time. But those are now becoming obsolete of course because of the environmental issues with the mercury and-or other poisonous materials.
Robert Calk Jr.
October 3, 2018 at 2:42 pm
Good job, Albert. Shop Jimmy has a nice little hot plate for $39.99 that they show working great in their video. https://www.shopjimmy.com/shopjimmy-led-strip-rework-station.htm
I have the new Backlight/Component Tester Model# TD3H that has the new board #KT4H inside. I can control the voltage and current with the Pot's on it. It also has a 1mA switch that keeps the current at 1mA or below.
Albert van Bemmelen
October 3, 2018 at 5:51 pm
Thanks for the link and info Robert. Did you also test the shopjimmy hot plate on double layer backlight strips like the ones in my LG repair article? Because I have another 260 degrees Celsius hotplate that was unable to hotfix the solder on the thicker two layer strips. Only hotfixing one layer copper boards and single side BGA chips was no problem with my heater plate!
Robert Calk Jr.
October 4, 2018 at 12:50 pm
Hi Albert,
I didn't mean buy one, I was just telling you about it for reference, that's all. It would be cheaper from Aliexpress or somewhere else anyway. I have never used it before, that's why I referred to their video. How are you liking your Hakko Omnivise?
Albert van Bemmelen
October 3, 2018 at 10:47 pm
Buying the $39.99 Shopjimmy hot plate would be a too costly venture for me Robert! Not only because Shipping costs are about an extra $23 dollar but also because of the absurd import charges for products bought from outside the EU !
It would have been a good product because apparently the hot plate had no problem with hot fixing the two layer copper LG led strips as the video must have showed. I saw the TD3H tester on Aliexpress you mentioned. It looks great too!
Albert van Bemmelen
October 4, 2018 at 9:37 pm
Understood Robert. Sadly the ShopJimmy Hot Plate can´t be bought on Aliexpress. The Hakko Omnivise was received within 2 days and is the ideal help in holding objects like my solder iron like you showed in your last repair safely. Sadly it won´t hold my Hot Air Heater because the Hot Air gun is too big for it. Still I have to agree that they could have put gold inside for the price that was asked.
Robert Calk Jr.
October 5, 2018 at 12:44 am
Yeah, they are pretty proud of the Omnivise! For holding the Hot-Air I would use my Panavise. You don't have a vise? I figured that some Chinese companies were making Hot plates like the Shop Jimmy one. They make everything else.
I just use my soldering iron mostly. I have the board preheater that uses air that I showed in the Hakko 888D iron repair. Using it and my Rework Station, LED strips would be a piece of cake. But in my Sanyo TV repair article that you will see soon, I just used my iron.
hongkong pom
October 3, 2018 at 3:01 pm
Thank you for that article.
I am looking forward to Samsung fix chapter 2 🙂
Albert van Bemmelen
October 3, 2018 at 5:56 pm
If there is a Samsung backlight problem to fix I will be happy to continue with another article fix chapter 2, Hongkong pom. But at the moment this repair was just about a fixed backlight of a 47 inch LG tv.
Parasuraman S
October 3, 2018 at 4:31 pm
Excellent is what I have say on this intricate work! Shows your skill and expertise!
Albert van Bemmelen
October 3, 2018 at 6:03 pm
Thank you Parasuraman for your kind comment. About this repair concerning the high power type 1 Watt 3537 Samsung backlight leds mentioned in the article only one of three new leds we tested on the led tester output voltage acted as if it was a complete short circuit, but afterwards still worked perfectly when tested on a 3V DC voltage. Which never happened when we used the other type 2828/3228 Samsung leds on the output of the led tester. Why we chose to use those in the repair thinking only they would work. But probably both types would have worked.
And although we called the led transparant diffusers in the article lenses, they in fact normally of course only spread the light coming from the backlight leds.
Lee
October 3, 2018 at 8:06 pm
I recommend turning the back lights down in the setting and not to have them at full brightness as this will make then last longer.
I've had my LG 47 6200 series since 2012 and it's still going.
Albert van Bemmelen
October 4, 2018 at 2:43 pm
Thank you Lee. We were about thinking doing that, but the owner left his IR remote at home when he brought in his tv for repair. We will have to tell the owner the message to turn the backlight brightness down. Good to know that your LG is still going after the backlight repair!
Andre Gopee
October 3, 2018 at 11:36 pm
Good Job Albert, Sometimes changing the LED's themselves solve the problem and sometimes they don't last very long. I have done this many times and they turn out fine but on some TV you have to replace the full strip. Thanks for the Video.
Albert van Bemmelen
October 4, 2018 at 2:56 pm
Thanks Andre. I am afraid that those backlight problems have become a new problem in the industry of tv repair only after they changed it from cfl tubes into todays leds.
And to save a dollar some manufacturers probably don´t care about how long the backlight will work after the warranty time has expired. The Video ´shown´ on the last 2 photos was just some online advertising about new Sony movies we can watch in the Cinema.
Eric Leung
October 5, 2018 at 11:18 am
Good article ! I have try to fix two Led TV with fault in Led bakight. Eventually the result is a tragedy, the panel broken durng the removal procedure.I want your advice how to remove the panel especial with the TV size over 42 inches in a safety. Thanks
Robert Calk Jr.
October 5, 2018 at 9:59 pm
Hi Eric,
I am right-handed. So the way I did it was to get a piece of ply board about 2'x3' and cover it with a thick towel. Then I put a suction cup a little ways back from the side I am in front of near the center, and lift the LCD screen up a little bit.
While I'm holding the screen up, I hold the covered ply board level in front of the screen with my left hand and slowly slide the screen onto the covered ply board. Then I carry them to a table and carefully slide them on the table leaving the covered ply board under the screen. When you want to replace the screen, just reverse the process to put the screen back into the LCD module or case. It worked for me! Cheers!
Albert van Bemmelen
October 6, 2018 at 4:12 am
Glad that you successfully managed to fix the backlight problem in your tv Robert! Probably fixing your vacuum cleaner was more difficult considering that replacing the motor or the brushes almost never is an easy to replace electronic part.
Robert Calk Jr.
October 6, 2018 at 8:13 pm
Actually, I couldn't find anything wrong with the vacuum cleaner. I took it completely apart and couldn't find anything wrong. Then I put it back together and it is working fine. I didn't think I had the electrical circuit overloaded, but maybe it was.
Albert van Bemmelen
October 7, 2018 at 1:54 am
It could be a break in the AC power cable that incidentally is beginning to fail, until it is a permanent open connection?
Robert Calk Jr.
October 7, 2018 at 10:03 am
Several years ago a puppy chewed the cord into, and I fixed it. I will check it and see if that could be the problem.
Eric Leung
January 15, 2019 at 9:14 am
Thank you idea. using your method, recently i disassemble a 48 inch wihtout damaged the panel by using suckion cup get it from China.
Albert van Bemmelen
October 5, 2018 at 3:50 pm
Sorry to hear you had bad luck with fixing two Led TV´s Eric. With the broken panel you probably meant the glass LCD TV screen? And if you accidentally broke the Led strips that would not be good either of course. The glass screen should be kept free from any mechanical outside force and best kept flat on a table to prevent it from accidental breaking. It was easy with the LG repair in the article because we started with removing the glass screen by placing it safely flat on a large table first. Best done with at least 2 persons to prevent any bending of the glass. Especially when it involves larger screen sizes! And by only touching the screen glass outside without making the inside of all inside plates filthy! And removing the glued ledstrips from the metal back inside also needs to be done with some care. After bad leds are replaced the adhesive tape on some of those strips may need new adhesive tape to firmly keep them in place again. We used very thin 3M double sided tape on those ledstrips that always is the best available quality to use. I do hope that this helps to still fix your Led tv´s Eric.
Beh
October 5, 2018 at 7:21 pm
Great repair ALBERT
Albert van Bemmelen
October 5, 2018 at 10:24 pm
Thanks Beh. As I wrote in the article I first hesitated to start repair on such a big size tv screen. But in the end all worked out for the best!
Yogesh Panchal
October 5, 2018 at 8:40 pm
Albert!
Congratulations! for repairing the backlit.
Bigger screen are very difficult to handle by single hand
once i have damaged the panel it was very thin like Paper and having crack on it.
Albert van Bemmelen
October 5, 2018 at 10:41 pm
Thanks Yogesh. It was that my shop owner friend had good faith in taking on this risky repair. I probably wouldn't have done it on my own myself but together it was a rather easy job. Afterwards I sold him my >320V automatic voltage ledtester for almost half price and bought some new tools including a new led tester. The tester that Robert suggested in his post above. Do not know if I would need that but I always keep an open mind in improvements on new equipment. Especially if that helps saving time and money in new repairs.
Humberto
October 17, 2018 at 12:55 am
Hi Albert, great repair and thanks for sharing your experiences.
Albert van Bemmelen
November 12, 2018 at 9:34 pm
The LG in this repair sadly failed partly a few weeks later when a few leds no longer gave enough light. And the backlight became a problem again.
So the best thing to do in these repair cases is to replace all original led strips by new ones. Especially if only the bad leds are replaced by new leds that are maybe are not equal to the types of leds originally used in the TV. Or if the recurring of the backlight problem is caused by other original leds that started to fail afterwards.
emmanuel
January 30, 2019 at 11:04 pm
GOOD WORK DONE,
Philip Turner
December 21, 2019 at 5:26 am
To test backlights, just use a number of 9 volt batteries in series to exceed the forward voltage of the required number of LEDs in a strip and a limiting series resistor for about 100mA for the voltage difference between the battery voltage and the LED forward voltage drop, and apply this to the strips one at a time. Then scratch the insulation off the LED lands, and apply one 9 volt battery and a 56 ohm resistor to each one to do the same thing. No need for expensive testers.
sandun
August 9, 2020 at 9:14 pm
Very good article Mr. Albert.
I found the same exact LG TV is repairing for backlight issue here, I hope this will be helpful for all : https://www.youtube.com/watch?v=6CVT9-Lts4o
REZA
December 19, 2020 at 12:18 pm
GOOD JOB MR.ALBERT
How many LEDs did you finally change?
What were the exact specifications of the LEDs?
Thanks