Don't Miss


Repairing Samsung LCD Monitors

By on March 22, 2012

samsung 943nx lcd monitor repair

Nowadays I found that the  Samung LCD Monitors like Syncmaster 943nx, 932 B plus, 943 Bwx and etc that was manufactured in the year 2008/9/10 a lot coming in to my workshop for repair. The complaint was usually no power, power blink and display shutdown. It seems that this batch of LCD monitors have a common fault. The cause of the above problem were bad filter capacitors (usually you have to replace few of them) and bad high voltage transformer. If the high voltage transformer have problem it would cause display to shutdown. One of the secondary resistance value will shoot up in ohms causing the feedback circuit to shut the display down.

Just compare the secondary winding ohms value and you will know if the high voltage transformer is good or bad. The Samsung boards was not complicated and it is a blessing to my company because the problems can be easily solved within minutes! If you found the e-caps that is rated 820uf 25 volt you can just put in 1000uf 25 volt and you are done.

If  you or your company is not repairing LCD Monitors I suggest that you include this equipment in your workbench because LCD Monitors generally are easy to fix. The only drawback is the LCD panel and some of the mainboard or parts that cannot be found in the market. Almost 60 to 70% LCD Monitor problems are due to bad electrolytic capacitors and the rest of the problems are power, inverter, backlight,  mainboard and LCD panel.

Likes(5)Dislikes(1)

19 Comments

  1. Humphrey Kimathi

    March 22, 2012 at 9:29 am

    Hi Jestine, Thanks for this info on solving LCD Monitors and Congratulations for the new face to your Blog.

    On this article you have said one can substitute e-cap rated 820uF 25 volt with the one rated ***100ouf*** 25 volt.

    I think you typed the last zero for the 1000uF as a letter "o" and hence is reading out like 100uF which would be too low as a substitute.

    Kind regards

    Humphrey

    Likes(1)Dislikes(1)
    • Jestine Yong

      March 22, 2012 at 8:55 pm

      Hi Humphrey,

      Thanks and I have amended it. Now could see your face in the comment box!

      Jestine

      Likes(1)Dislikes(1)
  2. beh

    March 22, 2012 at 10:21 am

    thanks MR YONG this article is very useful

    Likes(1)Dislikes(3)
    • Jestine Yong

      March 22, 2012 at 8:55 pm

      HI beh,

      You are welcome.

      Jestine

      Likes(1)Dislikes(1)
  3. Galib

    March 22, 2012 at 4:28 pm

    Yes, There is no way without learning to repair the LCD Monitor/TV . Because after few years later it will be hardly found CRT Monitor/TV like Black & White Television .

    And your new theme is looking gorgeous and attractive .

    Thanks

    Likes(0)Dislikes(0)
    • Jestine Yong

      March 22, 2012 at 10:10 pm

      HI Galib,

      Yes you are right. Thanks for the compliment about the theme.

      jestine

      Likes(0)Dislikes(0)
  4. Alex Lee

    August 30, 2012 at 2:43 am

    I've just fixed a Samsung 732N with slightly bad transformer (original should be around 1K to 1.1K, but the transformers measure 1.18K) by bypassing the FB (feedback) and OLP section. Because of that extra 80 Ohm difference, the inverter shutdown after 2 seconds. At the moment it operates properly (no more shutdowns). Will this be OK and can be used continuously, or should I replace the transformer or try the feedback tuning trick (will be bit tricky as it uses surface mount resistor)? Thanks...

    Likes(0)Dislikes(0)
    • Jestine Yong

      August 30, 2012 at 9:44 pm

      Hi Alex,

      Defeating the feedback could be dangerous. defeating it temporarily for testing is ok. I suggest that you get a new transformer so you will have a peace of mind when you go to sleep and need not worry about customer place catch fire and etc.

      Jestine

      Likes(1)Dislikes(0)
  5. Alex Lee

    August 31, 2012 at 1:41 am

    At the moment the monitor is running fine with both FB and OLP disabled. Currently "burning in" the monitor, to see if there are other weak or failing parts. The old transformer seems to be holding up well despite the slightly increased impedance, the display looks fine with no flicker and good brightness. Will ask the client if he could wait at least 2 weeks or more, since that will be the amount of time for brand new transformer to arrive.
    When I first examined the monitor there was a 5-band resistor which burned up and measured 220k but the color code indicated 2.29M (replaced it with 2.2M). Usually when resistors fail, their resistance increases or become open but this one does the opposite. Also this resistor was not mentioned in the service manual schematics nor was in the datasheet for the backlight controller! If you have a 732N, look for R31 (red-red-white-yellow-green). Any idea why Samsung added that resistor?

    Likes(0)Dislikes(1)
    • Jestine Yong

      August 31, 2012 at 9:44 pm

      Hi Alex,

      Sorry I do not have the schematic. As for the resistor the 220 k could be the original value because after a resistor went through heat the color may change. Yellow color could be orange and red color could be turn into brownish.

      Jestine

      Likes(1)Dislikes(0)
  6. Alex Lee

    September 1, 2012 at 5:00 am

    I have the service manual for that monitor, and guess what.. the inverter schematic is literally the same as the one in the backlight controller I.C datasheet including values and component labels (you can look it up, its FAN7310 or FAN7311 from Fairchild). As for the burnt resistor, the coloring did not change since the coating did not degrade from the heat. Here's the picture http://i.pictr.com/hns727uhcz.jpg  You can clearly see that the color bands are still intact despite the heat which caused discoloration of the surrounding area (becomes black'ish)...

    Likes(0)Dislikes(0)
    • Jestine Yong

      September 3, 2012 at 9:00 pm

      Hi Alex,

      If you see the surrounding circuit you will know that the resistor already gone through some heat. The color band is not vibrant anymore. Sometimes you may think that it did not change color but actually it already changed.

      Jestine

      Likes(0)Dislikes(0)
  7. Alex Lee

    September 1, 2012 at 5:03 am

    That picture links is "http://i.pictr.com/hns727uhcz.jpg", not sure why the "&nbsp" appeared at the back after posting.

    Likes(0)Dislikes(0)
  8. Lee Pham

    October 27, 2014 at 7:51 am

    I need schematic for repair LCD Sam Sung LS19A100NS/XS, Can you help me?

    Likes(0)Dislikes(0)
    • Jestine Yong

      October 27, 2014 at 11:18 am

      Sorry we don't carry any schematic. Try eserviceinfo.com

      Jestine

      Likes(0)Dislikes(0)
  9. hannes from south africa

    January 8, 2015 at 3:16 am

    Good day sir. I also have an 732n samsung that only shows the picture for one second. Can jou please send me an email so that I can reply with pics of the mother board. Then you can show me where to measure the transformer please.

    Likes(0)Dislikes(0)
    • admin

      January 10, 2015 at 9:21 am

      Hi Hannes,

      I suggest that you visit this link:

      https://www.jestineyong.com/test-lcd-inverter-transformer/

      Jestine

      Likes(1)Dislikes(0)
  10. Alexandre Barcelos

    December 28, 2016 at 9:44 pm

    This is a 334k precision resistor. The right colors are (orange, orange, yellow, orange and green(0.5% tolerance). Good look!

    Likes(0)Dislikes(0)
  11. ahmed essa

    July 26, 2017 at 1:34 am

    thank you very match

    Likes(0)Dislikes(0)

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Free Report