Sony KDL 42W705 backlight no sound, no picture

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  • sansiro2
    Member
    • May 2016
    • 18
    • United Kingdom

    #1

    Sony KDL 42W705 backlight no sound, no picture

    Hi guys, got a Sony 42W705 LED TV. Only get backlight but no picture. I get a one second blast of sound when I switch the TV on but then silence. I have changed the T Con and the main logic board to no avail. If I pull the LDVS off or the power cable to the main board while TV is on nothing happens.

    By the way for the T Con I matched the TX-5542T35C01 bit of the barcode, although the rest is slightly different.

    Any ideas what could be the cause?
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Sony KDL 42W705 backlight no sound, no picture

    Pictures of the whole back side of the TV so we can see all the 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

    • sansiro2
      Member
      • May 2016
      • 18
      • United Kingdom

      #3
      Re: Sony KDL 42W705 backlight no sound, no picture

      1st pic Power board with cover taken off
      2nd pic main board
      3rd secondary av board which clips on to main board
      The t con is underneath the secondary av board
      Attached Files

      Comment

      • budm
        Badcaps Legend
        • Feb 2010
        • 40746
        • USA

        #4
        Re: Sony KDL 42W705 backlight no sound, no picture

        I expect to see the FRC (Frame Rate Conversion) board between the main board and the T-CON board, it does not look like it has one.
        Did you check the DCV on both ends of the SMD fuse with ref to the chassis to see if the T-CON is getting the 12VDC? It is not going to be easy due to the location of the T-CON board.
        Last edited by budm; 06-14-2016, 12:58 PM.
        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

        • dick_barton
          Badcaps Legend
          • Aug 2015
          • 6642
          • Wales

          #5
          Re: Sony KDL 42W705 backlight no sound, no picture

          Have you checked F101 on the Tcon. Recently received a Tcon where the fuse was blown.
          Willing to help but I'm no expert.

          Comment

          • sansiro2
            Member
            • May 2016
            • 18
            • United Kingdom

            #6
            Re: Sony KDL 42W705 backlight no sound, no picture

            F101 appears to be fine. It's going to be awkward but where would I put the test probes to test if 12v is coming in? I assume tv needs to be switched on. Apologies been a since I done any electronics

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #7
              Re: Sony KDL 42W705 backlight no sound, no picture

              Black probe on the chassis Gnd, red probe on the fuse's ends (check DCV at both ends), TV has to be ON.
              Last edited by budm; 06-14-2016, 01:56 PM.
              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

              • sansiro2
                Member
                • May 2016
                • 18
                • United Kingdom

                #8
                Re: Sony KDL 42W705 backlight no sound, no picture

                Thanks I'll try to find a way to do this given the awkward positioning and let you know. Thanks

                Comment

                • nanias
                  New Member
                  • Aug 2016
                  • 6
                  • Portugal

                  #9
                  Re: Sony KDL 42W705 backlight no sound, no picture

                  Can you tell us the result?

                  I have the same problem.

                  Any one can help with a solution for this sintomes?

                  Thanks

                  Comment

                  • nanias
                    New Member
                    • Aug 2016
                    • 6
                    • Portugal

                    #10
                    Re: Sony KDL 42W705 backlight no sound, no picture

                    Please, If someone can help I appreciate because Sony is make me crazy...

                    I have already change the cable (and nothing change so that was not the problem):
                    SONY KDL-42W705B LVDS CABLE 1-848-110-11

                    This are the Symptoms in na attached video:
                    https://drive.google.com/open?id=0B_...UtEZklmYUliZzA

                    Can it be T-Con?

                    Thank you
                    Antunes
                    Lisbon-Portugal
                    Attached Files
                    Last edited by nanias; 08-18-2016, 03:18 PM. Reason: Add information

                    Comment

                    • ReeceyBurger123
                      Never Give Up !
                      • May 2014
                      • 7325
                      • Britain

                      #11
                      Re: Sony KDL 42W705 backlight no sound, no picture

                      Hi Nanias, what have you tested so far ? I also have the same set with a blown up Tcon I will diagnose it soon. Shame the guy NEVER BOTHERED to update the thread.
                      Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

                      https://www.facebook.com/Telford-Tel...7894576335359/

                      Comment

                      • nanias
                        New Member
                        • Aug 2016
                        • 6
                        • Portugal

                        #12
                        Re: Sony KDL 42W705 backlight no sound, no picture

                        In fact I dind't check nothing else because i am only a curious guy.

                        I read that could be a problem with the cable LVDS and I start there

                        Because the T-Com is more expensive i was trying by parts.

                        My afraid is that the problem can be the LCD panel. That's why I show the Symptoms to see if someone can help because i found a lot of people with the same problem.
                        Thks
                        Last edited by nanias; 08-19-2016, 05:39 AM.

                        Comment

                        • sansiro2
                          Member
                          • May 2016
                          • 18
                          • United Kingdom

                          #13
                          Re: Sony KDL 42W705 backlight no sound, no picture

                          Sorry guys I didn't get an email notification. But diagnosis was short circuited panel so TV is a goner. Shame on Sony, used to a brand you could rely on.

                          Comment

                          • nanias
                            New Member
                            • Aug 2016
                            • 6
                            • Portugal

                            #14
                            Re: Sony KDL 42W705 backlight no sound, no picture

                            Thanks sansiro2.

                            I made some more tests. I unplug one of the cables of T-Com and the result was this in the photo. No image. I do the same on the other cable and the result was the same. No image in none of the sides.

                            Any help?

                            Thanks
                            Attached Files

                            Comment

                            • sansiro2
                              Member
                              • May 2016
                              • 18
                              • United Kingdom

                              #15
                              Re: Sony KDL 42W705 backlight no sound, no picture

                              Sorry I have no idea. Maybe the technical guys can help.

                              Comment

                              • Moreno83
                                Badcaps Legend
                                • Jun 2014
                                • 2008
                                • The Netherlands

                                #16
                                Re: Sony KDL 42W705 backlight no sound, no picture

                                That looks like a bad t-con or bad panel! You need to measure the voltages as described above!

                                The T-con had a small fuse ( usually ) next to the LVDS port. Its very small and says something like "F101". Measure for continuity and measure the voltage.
                                I only repair Panasonic plasma tv's! Currently owning a TX-P55VT50 and still searching for a ZT60!

                                Comment

                                • nanias
                                  New Member
                                  • Aug 2016
                                  • 6
                                  • Portugal

                                  #17
                                  Re: Sony KDL 42W705 backlight no sound, no picture

                                  Originally posted by Moreno83
                                  That looks like a bad t-con or bad panel! You need to measure the voltages as described above!

                                  The T-con had a small fuse ( usually ) next to the LVDS port. Its very small and says something like "F101". Measure for continuity and measure the voltage.
                                  Hi Moreno83,
                                  Thank you so much. I will do that.

                                  My doubt is exactly that: T-con or bad panel. How can I be shure? Because if it is the panel everyone said to forget this TV and buy a new one. I will buy a T-con if I have the certainiity that this is the problem. I must import the T-Con and it will cost me about 50€ (used).

                                  Can you please tell me a test or a trick to eliminate this doubt? For exemple, if the fuse is ok can I assume that the problem is the panel?

                                  Can someone confirm that I have understand correct the possition of the probe of the multimeter? (I attach a picture).

                                  For someone who be interested i alsso attached a picture of the back of the TV.

                                  Thank you so much for everyone who can help.

                                  Nanias
                                  Attached Files

                                  Comment

                                  • dick_barton
                                    Badcaps Legend
                                    • Aug 2015
                                    • 6642
                                    • Wales

                                    #18
                                    Re: Sony KDL 42W705 backlight no sound, no picture

                                    Screw your tcon board back down. Black lead on chassis. Red lead on one side of the fuse and read dc voltage, then red lead on other side of fuse and read dc voltage and the readings should be identical.
                                    Willing to help but I'm no expert.

                                    Comment

                                    • nanias
                                      New Member
                                      • Aug 2016
                                      • 6
                                      • Portugal

                                      #19
                                      Re: Sony KDL 42W705 backlight no sound, no picture

                                      Originally posted by dick_barton
                                      ...the readings should be identical.
                                      If they are identical, can I assume the problem i have mencioned is on the LCD panel or that is nor conclusive and the problem can be at the T-Con but on other part (not the fuse).

                                      Forgive me the questions but I will open the TV and I would like to be conclusive at that time to see everything when the tv is open. Furthermore english is not my language and sometimes I don't understand words (i use Google translation...).

                                      Thanks again

                                      Comment

                                      • KEHT
                                        New Member
                                        • Apr 2016
                                        • 4
                                        • Ukraine

                                        #20
                                        Re: Sony KDL 42W705 backlight no sound, no picture

                                        Originally posted by sansiro2

                                        Any ideas what could be the cause?
                                        Yep, unscrew metal shields from the bottom of the LCD. Something like this.
                                        http://www.imagebam.com/image/219837503058597

                                        Check burned routes on the flexible cables. Something like this.
                                        http://www.imagebam.com/image/913b54503058762

                                        Congratulations, you got a s/c in your LCD. Yes, its time to buy a new TV

                                        Comment

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