Cynascan DS551LT4 backlights working but no video or menu

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

    #1

    Cynascan DS551LT4 backlights working but no video or menu

    Hi guys I honestly did not know whether to post this as a TV or a monitor - but it is being used with an HDMI converter as an outdoor TV at a local hotel swimming pool bar so I put it here

    @moderators - move this thread to monitors if preferred

    OK so I have a Dynascan DS551LT4 on my bench
    http://www.dynascanusa.com/product/5...ezel-ds551lt4/

    Anyone here familiar with these? It powers up, I have 12V from the little smps supply, and LED the backlights are working.

    It actually goes through a sequence of a green LED lighting on the logic board, then a green LEd flashes on the other board, then a red led flashes on the logic board, a relay clicks and the backlights come on. So it's not 'brain dead'.

    However I get no video, not even menu from the remote or the 'no signal' box. The hotel has two of these so I know the external hdmi converter box is working ok.

    Something has burnt out on a connector on one of the PCBs (the one where a green LED flashes once on power up) - but I don't know what this PCB does as I have not seen anything quite like this in LCD TVs. It looks more like a plasma X buffer or Y buffer board to me but this is LCD

    The two wires from the burnt out connector feed with some other wires into a cable and the other end of this cable disappears under the metal work at the corner of the LCD panel. There also looks to be a bad cap on he PCB near this burnt out connector. There seem to be similar cables going to other corners of the panel.

    There is another board maybe Tcon underneath the main logic board right at teh front of the panel, it's hard to see as it is partially obscured by metalwork.

    Please see pics and any advice welcomed, I'm a bit out of my experience with this one TBH.

    Cheers
    Rich

    PS I put Cynascan instead of Dynascan in the thread title but seem unable to edit it
    Attached Files
    Last edited by dicky96; 12-12-2017, 01:31 PM.
    Follow me on YouTube
    ------------------
    Learn Electronics Repair
    https://www.youtube.com/channel/UCFX...R8UZ2vg/videos
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Cynascan DS551LT4 backlights working but no video or menu

    You need to fix the burnt wires first.
    Yes, the T-CON board is under the metal works, you need to find out if it is fuse on the TOCN board is good or not and if you do have 12V feeding the fuse or not.
    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

      #3
      Re: Cynascan DS551LT4 backlights working but no video or menu

      Thanks Bud that's more stuff to strip down them. On further reflection that board with the burnt wires appears to be something to do with driving the LED backlights.

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

      Comment

      • budm
        Badcaps Legend
        • Feb 2010
        • 40746
        • USA

        #4
        Re: Cynascan DS551LT4 backlights working but no video or menu

        Originally posted by dicky96
        Thanks Bud that's more stuff to strip down them. On further reflection that board with the burnt wires appears to be something to do with driving the LED backlights.

        Rich
        https://www.badcaps.net/forum/attach...1&d=1513106807

        I cannot tell from the pictures as to where the burnt red wires go to, the picture is cut off.
        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

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #5
          Re: Cynascan DS551LT4 backlights working but no video or menu

          https://www.badcaps.net/forum/attach...0&d=1513106807
          I see two LVDS cables,you should check for 12V on those red wires of the LVDS51P , they should be for switched 12VDC that feeds the T-CON board.
          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

            #6
            Re: Cynascan DS551LT4 backlights working but no video or menu

            Didn't fix the burnt wires just yet but I removed a load more metalwork and checked F1 on the TCON board. It is intact and has 11.56V on it

            Rich
            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: Cynascan DS551LT4 backlights working but no video or menu

              TCON board
              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: Cynascan DS551LT4 backlights working but no video or menu

                Next test is to have one ribbon cable between T-CON and LCD panel connected one a time to see if you will get image on half of the screen.
                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: Cynascan DS551LT4 backlights working but no video or menu

                  With one cable diconnected (the left hand one looking at the screen from the front) I get a plain screen, one half slightly brighter than the other, though I tried this a few times and am fairly sure a least one time I got the whole screen evenly and brightly lit white

                  With just the other cable disconnected I get one side bright plain white and vertical stripes on the other.

                  I didn't see any video when I connected a hdmi-dvi adapter and a video source.

                  Even with no video input I should see a blue box on the screen saying 'no signal' as that is what the other one does at the hotel

                  Rich
                  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

                    #10
                    Re: Cynascan DS551LT4 backlights working but no video or menu

                    Next test will be putting all the cables back in place and use Oscilloscope to check the LVDS feeding the T-CON to see if they are present or not.
                    You may also have bad T-CON too.
                    Last edited by budm; 12-13-2017, 11:40 AM.
                    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

                      #11
                      Re: Cynascan DS551LT4 backlights working but no video or menu

                      That board with the burnt out connector - must be the dimming control for the backlights as it has connectors from the two big 42V 7.65A supplies, and a cable running to each corner of the panel where it vanishes under the metalwork. The only other connector on it is a 6 pin lead from the mainboard. The big 42V supplies don't connet to anything else so this is the LED driver.

                      The two burnt out connections, though they look bad they actually check out for continuity OK. So that is not the problem. I will of course fix them if I get the screen working.

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

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: Cynascan DS551LT4 backlights working but no video or menu

                        I see some Voltage test points on the T-CON that you should check:
                        Vin
                        Vcore
                        VGH
                        VGL
                        VCC18 (1.8V)
                        HVDD
                        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

                          #13
                          Re: Cynascan DS551LT4 backlights working but no video or menu

                          The pin pitch on the board is too fine for me to probe but I could probe the connectors

                          On one LVDS I could easily get to blue wire of twisted pairs.

                          There are 12 twisted pairs on this connector, I found high frequency data (seems to have some sort of 'frame' structure to it) on most of the twisted pairs at about +/1 1.5 Volts

                          One twisted pair was lower about +/- 1 Volt and a couple didn't seem to have data on them

                          On the other LVDS I could only get easily to the white wires. This again had 12 twisted pairs and 10 of trhem had high frequency data about +/- 1.5V slightly offset to the negative side

                          Not quite sure what I was expecting and whether there should be data on all the pairsso I will not surmise on these results

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

                          Comment

                          • dicky96
                            Sun Seeker
                            • Mar 2017
                            • 1825
                            • Spain

                            #14
                            Re: Cynascan DS551LT4 backlights working but no video or menu

                            Vin 11.53V
                            Vcc 3.319V
                            VGH (Odd/Even/R/F) all -5.01V
                            Vcc18 1.8V
                            HVDD 0.862V

                            and I spotted another test point VCOMLFB -0.130V

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

                            Comment

                            • freakaftr8
                              Badcaps Legend
                              • Oct 2012
                              • 3743
                              • USA

                              #15
                              Re: Cynascan DS551LT4 backlights working but no video or menu

                              HVDD looks dead to me this is the voltage driver to the film ICs on the ribbons on the panel. VCOM should have about 8v or so as well. May be a shorted panel or tcon
                              Last edited by freakaftr8; 12-13-2017, 02:59 PM. Reason: Added info
                              Did I leave the soldering iron on?

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Cynascan DS551LT4 backlights working but no video or menu

                                Those test points I see they are just round copper pads that you should easily probe them.
                                https://www.badcaps.net/forum/showth...&highlight=VGH
                                https://www.badcaps.net/forum/attach...3&d=1392518753
                                https://www.badcaps.net/forum/showpo...54&postcount=5
                                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

                                  #17
                                  Re: Cynascan DS551LT4 backlights working but no video or menu

                                  Originally posted by budm
                                  Those test points I see they are just round copper pads that you should easily probe them.
                                  I meant it is hard to probe the LVDS cables

                                  I disconnected the tcon cables in turn

                                  When I remove this one (see pic) I get a bright white background on the same side half of the screen and vertical lines on the opposite side half but HVDD goes to 8.25V

                                  So something on the panel or the PCB at the bottom edge of the panel is dragging HVDD down

                                  I still don't get any video on the screen
                                  Last edited by dicky96; 12-13-2017, 03:38 PM. Reason: clarification
                                  Follow me on YouTube
                                  ------------------
                                  Learn Electronics Repair
                                  https://www.youtube.com/channel/UCFX...R8UZ2vg/videos

                                  Comment

                                  • dicky96
                                    Sun Seeker
                                    • Mar 2017
                                    • 1825
                                    • Spain

                                    #18
                                    Re: Cynascan DS551LT4 backlights working but no video or menu

                                    forgot to add pic
                                    Attached Files
                                    Follow me on YouTube
                                    ------------------
                                    Learn Electronics Repair
                                    https://www.youtube.com/channel/UCFX...R8UZ2vg/videos

                                    Comment

                                    • freakaftr8
                                      Badcaps Legend
                                      • Oct 2012
                                      • 3743
                                      • USA

                                      #19
                                      Re: Cynascan DS551LT4 backlights working but no video or menu

                                      When you have good HDVD what's VCOM reading? Not VCOMFB,
                                      Did I leave the soldering iron on?

                                      Comment

                                      • dicky96
                                        Sun Seeker
                                        • Mar 2017
                                        • 1825
                                        • Spain

                                        #20
                                        Re: Cynascan DS551LT4 backlights working but no video or menu

                                        With ribbon disconnected VHDD 8.25V VCOM 7.1V

                                        With ribbon connected VCOM floated around like a capacitor charging or discharging. Went from -0.05V up to +0.15V approx then went back down to about -0.16V and stayed there This took maybe 15 seconds or more

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

                                        Comment

                                        Related Topics

                                        Collapse

                                        • Hakuu
                                          LG OLED77G1PUA - No Video / Audio after a TCON Board change and Software Update
                                          by Hakuu
                                          Hi There,

                                          This TV was auto switching off after few seconds with some vertical lines on the screen, so got a new TCON board and replaced it.

                                          After replacing the TCON board it was working fine and i set it up with everything, used for few hours, then had the bright idea to update the software on it. During the update process, TV switched off and now no audio or video. No relay switch sound.

                                          More Details

                                          TV Model - LG OLED77G1PUA

                                          Got the same exact TCON board from TVPartsToday and replaced it. But didnt transfer the EPPROM data (didnt...
                                          07-12-2023, 02:37 PM
                                        • Document Archive
                                          LCD LED TV Service Menu Codes
                                          by Document Archive
                                          ALL LCD LED TV SERVICE MENU CODES

                                          Service Menu Code with Board Name

                                          China Universal Board / Jumper Board Service Menu Code
                                          Changhong Ruba Service Menu Code
                                          Ecostar LED TV Service Menu Code
                                          Orient LED TV Service Menu Code
                                          Haier LED TV Service Menu Code
                                          TCL LED TV Service Menu Code
                                          Samsung LED TV Service Menu Code
                                          LG LED TV Service Menu Code
                                          Videocon LED TV Service Menu Code
                                          Supra LED TV Service Menu Code
                                          Toshiba LED TV Service Menu Code
                                          Symphony LED TV Service Menu Code
                                          Veste/ LED TV Service Menu Code...
                                          10-31-2024, 03:58 AM
                                        • lostone
                                          Looking for help with a Viewsonic VP230mb where the backlight comes on only momentarily
                                          by lostone
                                          Hello, I came here after finding some similar questions asked on other monitors and hope someone here can help me get an ancient Viewsonic VP230mp (23" 4:3 LCD) back to working condition.

                                          First a little background, I have a background in computer and electrical engineering, and I'm smart enough to know I know nothing about LCD displays and how they work. For this topic I'm as green as they come.
                                          When the display is turned on the viewsonic logo displays in the uppper left for 2 seconds then the screen goes black, the power LED is green (on) and when a computer is connected...
                                          05-19-2024, 11:40 AM
                                        • Aimbit
                                          JBL Flip Essentials - Bluetooth not connecting after a fall - video of board
                                          by Aimbit
                                          video: https://www.youtube.com/watch?v=S-xBu7m6SwE

                                          Hi all. I was given this JBL Flip Essential speaker that 'fell from about 8 feet' and then the bluetooth would no longer function. It seems to power on normally and responds to button presses, but it will not showup on bluetooth for any device I try to connect to it.

                                          The bluetooth daughter board has a 26mhz oscillator that I could not get to read the proper frequency so I tried replacing that to no avail. Thought maybe something was wrong with the bluetooth IC it's connected to, so I tried replacing that as well. None...
                                          10-28-2024, 09:29 PM
                                        • Ierwin
                                          Philips 58PUS7805 Menu working but no/weird picture from video sources
                                          by Ierwin
                                          Hello everyone,

                                          I got a 58pus7805 that shows some weird behavior.
                                          The menu and remote work fine and the picture is looking crisp and flawless while navigating the menu.
                                          However, when a video source is displayed the screen either goes solid green (HDMI), solid black (SAT TV) or shows some fragments on mostly green background (AVI Playback from USB).

                                          I tried to reinstall the firmware through the menu which was rejected saying it already had the latest version.
                                          I managed to install the latest official firmware by holding the control button while plugging...
                                          03-10-2024, 12:50 PM
                                        • Loading...
                                        • No more items.
                                        Working...