LG Slim TV With One Horizontal Line Solved

By on November 2, 2015



crt tv one horizontal line repair

 

 

 

 

 

 

 

one horizontal line repair

 

The complaint of this LG slim TV was one horizontal line across the screen. The common faults are usually bad vertical output IC, improper DC supply voltage, open vertical yoke coil, missing vertical signal from the vertical oscillator IC and also bad or leaky components in the surrounding area.

As usual, one need to open up the back casing in order to check on the circuit board. I was little surprised when I saw the vertical output IC was cracked and burnt-see the photo below:

vertical ic

 

Once you see a cracked IC, the first thing you need to do is to locate the part that was broken off. The reason for it is to track down the IC part number and this can eliminate the time of searching for the right part number.

burnt vertical ic

 

The part number was LA78141 and you can see the datasheet below:

LA78141 DATASHEET

Besides the burnt vertical output IC I also discovered two dead lizard-see the photo below. Probably these two lizards could have cause the vertical IC to blow.

4

 

I also noticed that the vertical output IC had some dry joints at the pins.

vertical ic dry joints

 

I continued to check on the corresponding components to make sure all the components are good.

clean soldering

vertical ic in crt tv

 

I had this new IC LA78141 for replacement and of course I had to clean the circuit board first before installation of the IC.

resolder ic joints

 

Ok, now the board is clean and I can power up the TV to see if the problem solved.

crt tv board lg

 

Guess that the one horizontal line problem was solved but there was another problem which is color patches in the TV screen. From experience, this kind of problem can be caused by bad CRT Tube, open degaussing coil, bad posistor or dry joints in the posistor area.

crt tv color patches

I checked on the degaussing coil and it shows low ohms reading which was good and there was no dry joints in the posistor.

posistor crt tv

good posistor crt tv

 

So I directly replaced the posistor and powered it On and guess what? The display was back to normal and two problems solved. If you want to learn CRT TV repair you can check on this ebook by Humphrey.

lg slim tv repair

suranga

 

This article was prepared for you by Suranga Bandara who owns an Electronics shop in Anuradapura, Sri Lanka.

 

Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.

P.S-  If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!

Note: You may check out his previous repair article in the below link:

http://www.jestineyong.com/samsung-subwoofer-damaged-by-a-mouse/

 

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20 Comments

  1. Mark

    November 2, 2015 at 10:56 am

    Hey Suranga,
    As usual, thanks for a well written and diagnosed repair. You provided a good diagnostic path.
    Amazing the wildlife people invite into their houses and TV's!
    RIP lizards!

    Likes(13)Dislikes(0)
  2. hongkongpom

    November 2, 2015 at 1:26 pm

    Great article!

    I think the problem is that the lizards only like the music channel 🙂

    Likes(6)Dislikes(0)
    • Pepper

      November 2, 2015 at 10:10 pm

      After skinning the lizard, dress and cut up the meat. Marinate it in sour orange juice, or in sweet orange juice acidulated with lemon juice. Add 1 teaspoon whole peppers and a dash nutmeg. After 3 hours, drain and wipe the meat dry. Season with salt, dip in beaten egg and in fine bread crumbs, and fry in deep, hot fat. Or it may be sautéed butter until it is brown and tender.
      Yum, yum, yum! (-;

      Likes(0)Dislikes(1)
  3. Albert van Bemmelen

    November 2, 2015 at 4:06 pm

    Hi Mr.Suranga, thank you for making me remember the degaussingcoil serie PTC posistor component. (That only demagnetizes/degausses the crt tube shortly after powering on the TV set, by attaching an AC Sinus current onto the degaussing coil via a PTC serie resistor that after heating up will stop the current through the coil). I saved a few of these degaussing coils that can be used in future projects, because they cost nothing and work fine on the AC Power line voltage. (and also because the insulated coil wire can be useful in other projects too).

    Likes(1)Dislikes(0)
    • Henrique Jorge Guimarães Ulbrich - Brazil

      November 3, 2015 at 3:22 am

      Albert, which type of projects can be done with the saved degaussing coils?

      Likes(0)Dislikes(0)
      • Albert van Bemmelen

        November 4, 2015 at 5:57 am

        Hi Henrique Jorge, it is not that any projects come to mind right now. But you can demagnetize tape heads and larger metals with such a coil. And saving these coils after dismantling those old CRT tv sets costs really nothing.
        And when you undo the tape round the coil, you get a very large insulated wire you can use to repair all sorts of transformers and similar devices that contain coils. They also use these coils to externally degauss Arcade CRT tubes that have magnetized tubes (that cause colour faults). On this link you are able to read about professional used Degaussers. http://degausser.com/. You can use the very strong produced magnetic fields to render your harddisk to completely unreadable before throwing it away if you have important personal data on it. Or use the wire to create a large Audio Induction Loop.

        Likes(3)Dislikes(0)
        • Henrique Jorge Guimarães Ulbrich - Brazil

          November 4, 2015 at 8:48 pm

          Thanks, Albert. Very useful information. I visited the link you've recommended about degaussing. This link is now in my browser favorites.
          Thanks again.

          Likes(2)Dislikes(0)
  4. Aziz

    November 2, 2015 at 6:00 pm

    Hi mr Suranga. thank you very much

    Likes(1)Dislikes(0)
  5. Gary

    November 2, 2015 at 8:01 pm

    Wow crt tv I have not seen for 2 years one of these.
    Good repairs info but plasma and Led tv and board swaps are all that shops near me do now - there are no good electronics engineers anymore in my country.

    Likes(0)Dislikes(0)
  6. Yogesh Panchal

    November 2, 2015 at 11:01 pm

    Suranga Congratulations! for your effort.

    Likes(0)Dislikes(0)
  7. Parasuraman S

    November 3, 2015 at 5:49 am

    Excellent! The posistor defect symptoms are new to me! Many thanks for sharing it! All the best!

    Likes(0)Dislikes(0)
  8. Ulises Aguilar Pazzani

    November 3, 2015 at 11:58 am

    Good fix Sir

    Likes(0)Dislikes(0)
  9. Humberto

    November 3, 2015 at 9:14 pm

    Good repair Suranga. In my country there are a great deal of CRT Monitors and TV sets.

    Likes(0)Dislikes(0)
  10. Aziz

    November 4, 2015 at 6:51 am

    Hi mr. Jestineyong , i got interested in the electronic age ten until now i know many things from your website thanks to you dear, i wish you success

    Likes(2)Dislikes(0)
    • Jestine Yong

      November 4, 2015 at 8:56 am

      Hi Aziz,

      You are welcome.

      Jestine

      Likes(1)Dislikes(0)
  11. Tito Kanshulu

    November 4, 2015 at 4:39 pm

    Good work Suranga and the ts is well explained.

    Likes(2)Dislikes(0)
  12. Saikrishna

    November 4, 2015 at 7:38 pm

    Very well explained, in fact i have a similar kind of problem in my old TV, i thoroughly examined exactly the way you described and i found the faulty IC LA78045.

    Now that i have located the fault, on the brief check i also came to know about the burn out resistor. But unfortunately am unable to find the Resistor value. Suranga can you help me finding the value of the resistor. Since my TV is old and unable to get the schematics for it.

    Your thoughts will be very helpful for me.
    Please, reply me.

    Thanks
    Saikrishna

    Likes(2)Dislikes(0)
  13. Parasuraman

    November 5, 2015 at 12:34 pm

    To know the values of burnt out resistors, pl read Jestine Yong's book on it. To my knowledge, there is no match to the packed infos and secrets that his books give!

    Likes(2)Dislikes(0)
  14. Derek

    November 6, 2015 at 12:17 am

    I had a problem with a new VHS VCR National NV-340EN ----the customer complained that the picture is very unstable. The problem was that a small mice got stuck in between the Guide Pole and the slot, in the play mode one guide pole could not reach the end because of the dead mice, after removing the dead mice and cleaning the area the set operated normal. small creatures usually creep inside TVs and other electronic equipment and create serious problems.

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  15. reza

    November 13, 2015 at 3:17 am

    hi Suranga Bandara
    thank u very much for good article.

    Likes(0)Dislikes(0)

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