TD Systems K55DLT6F Backlights OK but no picture

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • dicky96
    Sun Seeker
    • Mar 2017
    • 1825
    • Spain

    #1

    TD Systems K55DLT6F Backlights OK but no picture

    Hi guys I got this TD Systems K55DLT6F 55" LED TV here

    It has back lights but just a very dark blue screen, no image no menus.

    Disconnecting the left hand (looking from the back) TCON cable gives a white screen, or sometimes a blue screen on the same side of the panel as the disconnected TCON and dark on the other side

    Disconnecting the right hand TCON cable gives a good picture on the other side of the panel and a white screen that gradually fills out to the edges on the same side as the disconnected TCON - see pics

    Ther are test points on the HV77DA TCON board but none are marked with obvious voltage names

    Is that anything other than a faulty panel?


    Rich
    Attached Files
    Last edited by dicky96; 09-03-2018, 05:41 AM. Reason: correction
    Follow me on YouTube
    ------------------
    Learn Electronics Repair
    https://www.youtube.com/channel/UCFX...R8UZ2vg/videos
  • dicky96
    Sun Seeker
    • Mar 2017
    • 1825
    • Spain

    #2
    Re: TD Systems K55DLT6F Backlights OK but no picture

    Anybody? IIRC if I disconnect one TCON and the other side gives a good picture, but I have no image at all with both TCON connected then I have a faulty panel?

    Thanks
    Rich
    Follow me on YouTube
    ------------------
    Learn Electronics Repair
    https://www.youtube.com/channel/UCFX...R8UZ2vg/videos

    Comment

    • vinceroger69
      Badcaps Legend
      • Mar 2012
      • 6714
      • uk

      #3
      Re: TD Systems K55DLT6F Backlights OK but no picture

      on the lcd panel pcb on the side that shows a white screen have you checked for shorted smd capacitors theres been a couple of threads people have one on the bad side

      Comment

      • dicky96
        Sun Seeker
        • Mar 2017
        • 1825
        • Spain

        #4
        Re: TD Systems K55DLT6F Backlights OK but no picture

        No shorts across any of the caps on the panel PCB. All the 0 ohm smd 'resistors' read OK too

        I also checked from the all the test points on the TCON for shorts to ground. None found.

        Richard
        Follow me on YouTube
        ------------------
        Learn Electronics Repair
        https://www.youtube.com/channel/UCFX...R8UZ2vg/videos

        Comment

        • budwich
          Badcaps Legend
          • Jul 2015
          • 3097
          • Canada

          #5
          Re: TD Systems K55DLT6F Backlights OK but no picture

          "normally", as you see when a cable is disconnected from the panel, the panel shows "white". It would appear from the "fringe" on the bad side that panel has an issue along the side and "smear of black" is showing.... it is like a similar effect if you press on an LCD screen. What is the history of the set? Are there tabs bonded along each side?

          Related to the above "guess", if power is able to get to the panel but not able to "drain" then the LCD remains powered and shows black... its possible that you may have a bad connection / "improper" smd cap as opposed to shorted one.
          Last edited by budwich; 09-04-2018, 07:04 AM.

          Comment

          • dicky96
            Sun Seeker
            • Mar 2017
            • 1825
            • Spain

            #6
            Re: TD Systems K55DLT6F Backlights OK but no picture

            Hi Bud
            When I remove the cable from the 'good' side it is white all the way to the edges. The bad side is black.

            When I remove the cable from the 'bad' side, the good side shows an image, the bad side is white, but as you say with dark fringes to the edges that gradually go white over several seconds. So the white area gradually fills the edges of the screen.

            With both cables attached all is black.

            The set is less than a year old but the bar who it belongs to lost the paperwork/receipt.

            It's used outdoors for the football games but moved in at night.

            I didn't look for tab bonds down the sides, I will look in the morning.

            My guess is that condensation could be the culprit here. We don't get any rain here (well maybe 3 inches a year and most of that falls in February) but it's common to see condensation covering parked cars in the mornings even though the night time temperature rarely goes much below 20C. I guess we have a very high 'dew point'
            Last edited by dicky96; 09-04-2018, 10:55 AM.
            Follow me on YouTube
            ------------------
            Learn Electronics Repair
            https://www.youtube.com/channel/UCFX...R8UZ2vg/videos

            Comment

            • dicky96
              Sun Seeker
              • Mar 2017
              • 1825
              • Spain

              #7
              Re: TD Systems K55DLT6F Backlights OK but no picture

              @budwich
              I can't easily check if there are any tab bonds at sides without dismantling the whole set.

              There are no cables going to the sides of the screen that I can see from the mainboard or TCON. There are 6 tab bonds from each of the panel PCBs at the bottom

              This is the panel model number (I think) if that helps
              Attached Files
              Follow me on YouTube
              ------------------
              Learn Electronics Repair
              https://www.youtube.com/channel/UCFX...R8UZ2vg/videos

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #8
                Re: TD Systems K55DLT6F Backlights OK but no picture

                Your LCD panel has integrated T-CON which is part of the tab bonding boards.
                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

                • dicky96
                  Sun Seeker
                  • Mar 2017
                  • 1825
                  • Spain

                  #9
                  Re: TD Systems K55DLT6F Backlights OK but no picture

                  Originally posted by budm
                  Your LCD panel has integrated T-CON which is part of the tab bonding boards.
                  Hi can you elaborate on what that means please

                  There is a lvds to the TCON PCB and ribbons connecting to the lcd panel pcbs just like I usually see

                  cheers
                  Rich
                  Last edited by dicky96; 09-05-2018, 03:45 PM.
                  Follow me on YouTube
                  ------------------
                  Learn Electronics Repair
                  https://www.youtube.com/channel/UCFX...R8UZ2vg/videos

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: TD Systems K55DLT6F Backlights OK but no picture

                    Ops, sorry I got your thread mixed up with another thread. Please disregard my comments.
                    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

                    • Andrew F. Ali
                      Badcaps Legend
                      • Jan 2014
                      • 2450
                      • Trinidad & Tobago

                      #11
                      Re: TD Systems K55DLT6F Backlights OK but no picture

                      The flat cable from the T-Con Bd. to the Source Bd--are they in good condition? Do they have any abnormal marks on them? Did you try switching left and right flat cables to see if the problem remains on the originally bad side?

                      Comment

                      Related Topics

                      Collapse

                      • Fly_Among_Stars
                        VIZIO E70-E3 Half picture with half TCON
                        by Fly_Among_Stars
                        Hi,
                        I have a VIZIO E70-E3.
                        Symptoms: Black screen, no picture, but LED backlights are working.
                        I probed the power board and voltages are as listed on the board.
                        Main board appears fine, too.
                        I believe the problem is either a bad T-CON board, or connection to LCD, or bad LCD.
                        There are two separate ribbon cables feeding the LCD.
                        If both are connected, the screen is black.

                        If only the ribbon cable that feeds the right side of the screen (when viewed from the front) is disconnected, the left side of the screen shows picture and...
                        04-24-2023, 08:20 PM
                      • Helikvar
                        Hisense 58A6KV
                        by Helikvar
                        No picture ,tv appears to turn on and off using remote as standby led goes from red to nothing when on and red again when off
                        . Backlights also light up when tv is powered on.
                        Removing panel ribbon cable from left side screen still dark.
                        Removing panel ribbon cable from right side the right panel is white and left panel is dark but within a few seconds the left panel has a large green vertical bar and beside it many thin red lines.This whole screen dims down to dark within a few seconds and the right side slowly turns white again.
                        . Tcon gets 12 volt
                        . Tried taping...
                        02-21-2025, 03:52 PM
                      • Awsmessymail
                        Vizio E701i-A3 backlight only and now no backlight
                        by Awsmessymail
                        Hello all,
                        I’ve tried to repair TVs in the past with some luck. Toms repair manuals got taken down and now thats a bit harder.
                        I picked this TV up hoping for a quick fix. When the TV would power on, only the backlights would come on. The owner told me they heard loud screeching before it shut off. This alone makes me want to think the main board has an issue.
                        As I researched, I found the TCON/driver boards were an issue on this unit. I went in troubleshooting the TCON but found good voltages on the TCON. I followed shop jimmys guide to test the transistors and they seem okay....
                        02-13-2024, 11:04 PM
                      • shelby5041
                        Samsung LCD TV no picture backlight on no 12v at tcon
                        by shelby5041
                        hi
                        i have a samsung lcd tv

                        it powers on with sound and backlight but no picture

                        all voltages from PS are good 12v 3.3v and 5v

                        whats odd is that at the tcon i tested voltage across the fuse on the tcon and i get 0v

                        i figured main board issue..so i ordered a used main board....when i put replacement main board in i still have same issue

                        no 12v at the tcon fuse

                        i disconnect the panel ribbon cables to rule out any panel issues and i still have no 12v at the tcon fuse

                        the odds of having 2...
                        10-08-2021, 08:21 AM
                      • stinger
                        Samsung UN70TU6980FXZA no sound no picture but does have backlights
                        by stinger
                        When I turn tv on, the backlights come on but there is no sound or picture. I have read that these tv's have problems with the panels going bad but the "no sound" has me questioning if the main board is bad. Is there a way to troubleshoot the main board to determine if that is the problem?
                        04-17-2024, 03:06 PM
                      • Loading...
                      • No more items.
                      Working...