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Backlight rare white rings. Samsung 50in 4K TV

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    Backlight rare white rings. Samsung 50in 4K TV

    I have a Samsung 50KU6000 4K TV model 2017 with this rare problem of backlight.
    Everything works ok, all backlight leds work but in bright parts of every image appears those white rings.
    I attached a image of a plain white picture; in darker movies is much less noticeable. Some rings are more noticeable than others, but almost every led produce those rings.
    I tested different levels of backlight setting from 0 to 20.... same results
    Opened the TV and it have 6 rows with 13 leds each. The power supply have 2 output lines with 120Vcc each, each for 39 leds of 3V....everything seems ok
    The led's lens are good attached to each led.

    Have you ever see this problem? Do you have any suggestion?
    I don't want to buy a whole new backlight and maybe I spend that money and not resolve the problem

    I appreciate any input in advance
    Defective backlight or something else?
    Attached Files

    #2
    Re: Backlight rare white rings. Samsung 50in 4K TV

    Interesting, haven't seen anything like it before, will be watching this one.
    Last edited by nomoresonys; 02-26-2019, 06:46 PM.

    Comment


      #3
      Re: Backlight rare white rings. Samsung 50in 4K TV

      What is the history of this set, is this a previous screen repair or otherwise.

      Comment


        #4
        Re: Backlight rare white rings. Samsung 50in 4K TV

        that is what I am thinking too... maybe that tv had been apart before and the diffuser sheets aren't in the right order or some are missing. Another thing that came to my mind is, someone changed the backlight strips from some different tv.
        Last edited by CapLeaker; 02-26-2019, 09:09 PM.

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          #5
          Re: Backlight rare white rings. Samsung 50in 4K TV

          May be look at the P/N on the strips to see if they are made for your LCD panel model number.
          Never stop learning
          Basic LCD TV and Monitor troubleshooting guides.
          http://www.badcaps.net/forum/showthr...956#post305956

          Voltage Regulator (LDO) testing:
          http://www.badcaps.net/forum/showthr...999#post300999

          Inverter testing using old CFL:
          http://www.badcaps.net/forum/showthr...er+testing+cfl

          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
          http://s807.photobucket.com/user/budm/library/

          TV Factory reset codes listing:
          http://www.badcaps.net/forum/showthread.php?t=24809

          Comment


            #6
            Re: Backlight rare white rings. Samsung 50in 4K TV

            I bought the TV new in early 2017. And never left my house, and never had been touched by any technician. Everything original, not refurbish.
            In mid 2018, just after passed the 12-month warranty, I started to notice only 3 of those white rings (in the upper left corner, now those 3 rings are among others, but are more noticeable)
            During the last 6 months, other rings are appearing.
            The TV is wall mounted in my living room; never exposed with sun light or humidity.
            And TV have a high usage; maybe 6 hours a day, every day.
            The white rings don’t depend in the usage hours; looks the same just turned on after a day off or after 24 hs straight on.

            After months of this problem I wanted to put my hands in the TV; I have some electronic background but never opened a TV before. I saw some internet videos and talk with some TV repair store employees.
            This weekend I opened the TV for the first time; I was expecting some deformation in led strips or lens because I supposed that the problem was led strip detached to the frame and too close to the screen…was not the case.
            I found led strips well attached to the frame and lens well attached to the leds.
            Every led works (78 leds; 6 strips of 13 leds each); I found that 3 o 4 of them have a bluish color (you can see that in the picture; even if the picture didn’t catch all of the 78 leds).
            The supply board BN94-10712A have 4 wires to leds (1+ 1- 2+ 2-) measured with the main board disconnected and supply board connected to leds and found 120Vcc between 1+ and 1- and 120Vcc between 2+ and 2-
            I cleaned every len even if they look pristine (two of them I detached the len from the led to clean it better in both sides and glue again to the led, but no noticeable effect)
            I didn’t touch the white sheets between the leds and the screen…they didn’t look dirty at all…next time I open the TV I will try to clean those white sheets anyway. A repair employee recommends me doing so because could be like invisible dirt? Is that possible?
            The led strips are V6DU-500DCB-R2 (16.03.14)
            Thank you in advance for your interest.

            Comment


              #7
              Re: Backlight rare white rings. Samsung 50in 4K TV

              this issue happen because of wall mounting, and i think the TV wasn't straight standing, just little curve to down. the first reflection hard plastic plate by time at this condition got moved forward the screen, so the distances between it and the led lens became bigger, this why the issue start at the top left then more.

              you need after take it apart. the hard plastic one fix it with type a round or you fix it tight to chassis then the other diffuser sheets on it in order and fix them all together with type a round

              by the way this hard plastic it had 2 surfaces one of them are very fine. this surface should be to the top
              Last edited by Diah; 02-27-2019, 01:46 AM.

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                #8
                Re: Backlight rare white rings. Samsung 50in 4K TV

                Not due to wall mounting
                contact samsung and get it replaced (major fault)

                Comment


                  #9
                  Re: Backlight rare white rings. Samsung 50in 4K TV

                  If your leds are starting to turn blue they are probably near end of life, many times backlights are set to vivid or turned up full to 20 etc. this is an led killer if tv is still under warranty make them replace it for sure if not could try replacing backlights but be warned, it's very very easy to break the flimsy screen in the process, suction cups are a good tool for such a job.

                  Comment


                    #10
                    Re: Backlight rare white rings. Samsung 50in 4K TV

                    Originally posted by chrismurphy View Post
                    Not due to wall mounting
                    contact samsung and get it replaced (major fault)
                    funny to read this.. you called it major fault.?? but you never explain where are the fault...

                    Comment


                      #11
                      Re: Backlight rare white rings. Samsung 50in 4K TV

                      Very interesting problem, especially if the TV has not been serviced or repaired before.

                      Are you sure these rings have not always been there? Perhaps they were more subtle?

                      It looks like ALL the LEDs have rings so I'm not sure they are appearing "one by one".

                      You said the TV is wall mounted? Does it angle downward? or is it perfectly level?

                      If the TV is at a slight downward angle, I'm inclined to think there is an issue with the diffuser sheets separating from one another and creating reflections that amplify the effect.

                      What happens if you press the LCD screen gently in different areas of the screen? Do the rings get better or worse?
                      Last edited by Unspun01; 02-27-2019, 03:20 PM.

                      Comment


                        #12
                        Re: Backlight rare white rings. Samsung 50in 4K TV

                        TV has around 26 month old, is out of warranty.
                        AND THE WALL MOUNT IS SLIGHT DOWNWARD ANGLE (maybe 5º) pointing to the couch 😊
                        Thank you guys I think you nailed it

                        Originally posted by Unspun01 View Post
                        Are you sure these rings have not always been there? Perhaps they were more subtle?

                        It looks like ALL the LEDs have rings so I'm not sure they are appearing "one by one".
                        What happens if you press the LCD screen gently in different areas of the screen? Do the rings get better or worse?
                        Yes; I have a very trained eye...the first 12-15 month no rings at all; then 3 rings appeared; and after some months with only 3 rings then the rest; maybe not exactly one by one, many at the same time gradually going worse.
                        Is difficult to press LCD and see the effect because as soon as you press the image get distorted badly; but pressing from the screen It doesn't seem to be any significant gap between the screen-diffuser sheets-diode frame plastics separators. But maybe some millimeters are enough to cause this.

                        Originally posted by Diah View Post
                        need after take it apart. the hard plastic one fix it with type a round or you fix it tight to chassis then the other diffuser sheets on it in order and fix them all together with type a round
                        Thank you very much; I don't understand the procedure you described (maybe is my limited English language ) I don't understand “type a round”
                        Could you explain little longer or with other words how to make that first hard white plastic get closer to the frame leds?

                        Comment


                          #13
                          Re: Backlight rare white rings. Samsung 50in 4K TV

                          Originally posted by pablo712 View Post
                          TV has around 26 month old, is out of warranty.
                          AND THE WALL MOUNT IS SLIGHT DOWNWARD ANGLE (maybe 5º) pointing to the couch 😊
                          this what meant and other explained it with clear english.. but still the meaning same.
                          1- you can take out the panel absolute totally out from the set,
                          2- the socket between PSU ( power supply ) and MB ( Main Board ) if you disconnected it the LED Back light will turn on so you can check yours work always with out panel

                          3- the hard plastic it standing on legs pin at the middle of chassis . check if they are all in place

                          4- the top of chassis had 1 cm wide place where the hard plastic sitting at it. this need to fix it that the plate will never move. by clues or any method which not effected out side this 1cm wide i mentioned for example.

                          5 same way the diffuser you bring them back in order and fix them

                          hard plastic plate had 2 surfaces the fine one should be on the top forward the to the LCD...

                          Comment


                            #14
                            Re: Backlight rare white rings. Samsung 50in 4K TV

                            The only time I have seen something similar is when an led was replaced and the lens was not installed properly, So maybe something has caused the led lenses to move or maybe fall off?
                            I doubt the diffuser sheet is to blame for this type of problem, it's to uniform across the whole screen.

                            Comment


                              #15
                              Re: Backlight rare white rings. Samsung 50in 4K TV

                              i would call the manufacturer . they might want to take a look at it .

                              Comment


                                #16
                                Re: Backlight rare white rings. Samsung 50in 4K TV

                                Even though the OP has "tested" various levels of backlighting, what he indicated in all the use what the settings were during that time. It might provide some insight as to what may have caused the issue. Changing the level after the fact / damage, isn't likely to help.

                                Comment


                                  #17
                                  Re: Backlight rare white rings. Samsung 50in 4K TV

                                  Are the rings more visible the "bluer" the LEDS get?

                                  The reason I ask, here's my theory: Blue light is towards one the edge of the visible spectrum. (think how hard it is for your eyes to focus on true blue signs at night). If the LEDs shift to the blue side of the spectrum with age then the optics of the lenses cannot disperse/direct the "incorrect wavelengths" as designed. The lenses don't work right, therefore casting rings on the diffuser sheets. I suspect there is a correlation between how blue the light is and how visible the ring is from that LED.

                                  I've seen those rings before in a set that had significant blue'd lights. But they were all equally blue, so I didn't give it much thought at the time and just used the LCD in another TV.
                                  Last edited by jjanssen7; 02-28-2019, 01:20 AM.

                                  Comment


                                    #18
                                    Re: Backlight rare white rings. Samsung 50in 4K TV

                                    Looking again at your first post, I don't see any correlation. So it's just a wonky theory... Maybe with age/heat the lenses themselves are changing their optical properties?

                                    Comment


                                      #19
                                      Re: Backlight rare white rings. Samsung 50in 4K TV

                                      Do you smoke in the room? Have seen similar to this a couple of times, both occasions the customer were smokers.

                                      Comment


                                        #20
                                        Re: Backlight rare white rings. Samsung 50in 4K TV

                                        For davph: I vape with an e-cigarrete; but very few times inside the house. What could happen with that?
                                        For other questions: most of the life of the TV the backlight setting was 20/20… I didn’t know that could harm the TV back then.…Now I have set it to 13/20… but any setting produces rings

                                        I opened the TV again and NO SUCCES.
                                        No curvature of that hard plastic diffuser; If I press the diffuser few millimeters against the leds that reduce the rig’s diameter and in opposite way if I lift the diffuser that result in a bigger diameter rings.
                                        No way that plastic diffusers (hard and sheets ones) could be misplaced or rotated because marks in plastic and rubber borders only let those fit in the right way only.
                                        I also cleaned diffusers (both sides of each one) and led lens…no change at all
                                        I think the only thing left to do is change the whole 6 strips of leds… I only found a workshop that sell those “used” from a broken screen TV at u$s 60 with no refund…
                                        I attached some photos with all the diffusers; then with only the hard plastic one; then pressing and lifting that diffuser; also with no diffusers
                                        Attached Files
                                        Last edited by pablo712; 03-05-2019, 06:34 PM.

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