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Sanyo DP46848 screen half dark

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    Sanyo DP46848 screen half dark

    I have this TV that when I turn it on the left side of the screen is dark, then after about 10 to 20 minutes the left side (which I think are the backlights) will start to flicker and then will come on and stay on until I turn off the TV. Then if I turn it back on it does the same thing.
    Any help would be appreciated

    Thanks in advanced

    #2
    Re: Sanyo DP46848 screen half dark

    Forgot to attach pics

    middle pic is after 20 mins or so
    Attached Files

    Comment


      #3
      Re: Sanyo DP46848 screen half dark

      I don't have a definitive answer and have way less experience on the TVs versus the computer LCDs, but you probably will have to take the TV apart and post pictures of the internal boards. Look for bad capacitors, poor solder joints, etc.
      Last edited by retiredcaps; 04-25-2011, 01:16 PM.
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        #4
        Re: Sanyo DP46848 screen half dark

        Originally posted by rhino18e View Post
        I have this TV that when I turn it on the left side of the screen is dark, then after about 10 to 20 minutes the left side (which I think are the backlights) will start to flicker and then will come on and stay on until I turn off the TV. Then if I turn it back on it does the same thing.
        Any help would be appreciated

        Thanks in advanced
        In every case problems such as this are due to malfunctions of the panel in some way. Power supply problems seem remote to this effect.

        T-Con is unlikely. Connections from the T-con to the panel are a possibility.

        Comment


          #5
          Re: Sanyo DP46848 screen half dark

          Definitely looks like backlights to me. Unusual that it wouldn't trigger an inverter shutdown. A picture of the back of the TV (with the cover off) would be a big help.

          PlainBill
          For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

          Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

          Comment


            #6
            Re: Sanyo DP46848 screen half dark

            Pics of the power supply and video card

            solder joints look good on the power supply
            Attached Files

            Comment


              #7
              Re: Sanyo DP46848 screen half dark

              The pins on the two inverter transformers (1st photo upper left) look a little discolored (2nd photo). Suggest you try resoldering all the inverter transformer pins with fresh solder. Also, resolder the leads of the two heat-sinked mosfets to the right of the inverter transformers.

              Comment


                #8
                Re: Sanyo DP46848 screen half dark

                The power and signal cards are in a depression of the back cover, I took them out and hooked them up like the back cover isn't there
                Attached Files

                Comment


                  #9
                  Re: Sanyo DP46848 screen half dark

                  Originally posted by jetadm123 View Post
                  The pins on the two inverter transformers (1st photo upper left) look a little discolored (2nd photo). Suggest you try resoldering all the inverter transformer pins with fresh solder. Also, resolder the leads of the two heat-sinked mosfets to the right of the inverter transformers.
                  That area is a little darker. I will resolder all points you made, I noticed there is a solder bridge near the one mosfet and a diode should I fix this too?
                  Attached Files

                  Comment


                    #10
                    Re: Sanyo DP46848 screen half dark

                    I circled a couple of what looks like solder ring cracks to me (or is it the lighting)? You have the best view and if you use a 10x magnifier you might see more?
                    Attached Files
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                      #11
                      Re: Sanyo DP46848 screen half dark

                      This tv has master and slave inverters. I have seen these shut down when ccfls get to a certain point of failure and it only takes a couple. The pattern looks odd though and not sure of the bulb layout on this panel.

                      Comment


                        #12
                        Re: Sanyo DP46848 screen half dark

                        Originally posted by cadiman View Post
                        This tv has master and slave inverters. I have seen these shut down when ccfls get to a certain point of failure and it only takes a couple. The pattern looks odd though and not sure of the bulb layout on this panel.
                        By the pictures in post #8 the inverters are on either side of the panel. That suggests the CCFLs run horizontally, which makes it likely that this is NOT a CCFL problem and Village Electronics is right.

                        PlainBill
                        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                        Comment


                          #13
                          Re: Sanyo DP46848 screen half dark

                          Originally posted by PlainBill View Post
                          By the pictures in post #8 the inverters are on either side of the panel. That suggests the CCFLs run horizontally, which makes it likely that this is NOT a CCFL problem and Village Electronics is right.

                          PlainBill
                          I took the black plastic off the sides and there are master and slave inverters. I resoldered the power supply transformers and the mosfets and have yet put it back together to see if anything changed. I found the specs for the panel if that helps. Will post results when reassembled.
                          Attached Files

                          Comment


                            #14
                            Re: Sanyo DP46848 screen half dark

                            Originally posted by retiredcaps View Post
                            I circled a couple of what looks like solder ring cracks to me (or is it the lighting)? You have the best view and if you use a 10x magnifier you might see more?
                            That's refection, I took the picture outside in the shade. I looked at it with a 4x magnifier and it looks good.

                            Comment


                              #15
                              Re: Sanyo DP46848 screen half dark

                              After resoldering the transformers and mosfets there is no change. Could it be the master or slave boards?

                              Comment


                                #16
                                Re: Sanyo DP46848 screen half dark

                                I apologize in advance for bringing up an old thread, but I'm having the exact same issue. I've done a bit of troubleshooting on my own. I removed the main board (video card, signal card, whatever you call it) and looked around for dark spots which I didnt find any. The problem goes away when you tap on the upper left corner of the housing around the display which makes me think its some sort of connection problem. I hooked the signal board back up but I didnt screw it in all the way. I wanted for the problem to occur and then wiggled the signal board to see if the problem went away, and it did not. So that almost verifys for me that it is not a problem with the signal board. Is it worth it to remove then entire back panel and check for loose connections or anything else? What else should I look for? Is there a part that I can replace myself fairly easily? Let me know if there is anything else you would like me to try, if you need pictures of anything.

                                Thanks

                                Comment


                                  #17
                                  Re: Sanyo DP46848 screen half dark

                                  Also, I know it is not a backlight issue as the top part of the screen goes a little glitchy. Its hard to explain, so here is a video I took of the problem a while back. http://www.youtube.com/watch?v=9Mi-q8kMAwc

                                  Comment


                                    #18
                                    Re: Sanyo DP46848 screen half dark

                                    Originally posted by CamBlack View Post
                                    I apologize in advance for bringing up an old thread, but I'm having the exact same issue. I've done a bit of troubleshooting on my own. I removed the main board (video card, signal card, whatever you call it) and looked around for dark spots which I didnt find any. The problem goes away when you tap on the upper left corner of the housing around the display which makes me think its some sort of connection problem. I hooked the signal board back up but I didnt screw it in all the way. I wanted for the problem to occur and then wiggled the signal board to see if the problem went away, and it did not. So that almost verifys for me that it is not a problem with the signal board. Is it worth it to remove then entire back panel and check for loose connections or anything else? What else should I look for? Is there a part that I can replace myself fairly easily? Let me know if there is anything else you would like me to try, if you need pictures of anything.

                                    Thanks
                                    This is almost certainly a bad bond between the flex circuit that runs from the tcon to the glass lcd panel. Some people have had limited success inserting foam to force a better contact, although this is at best a temporary patch.

                                    PlainBill
                                    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                                    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                                    Comment


                                      #19
                                      Re: Sanyo DP46848 screen half dark

                                      Originally posted by PlainBill View Post
                                      This is almost certainly a bad bond between the flex circuit that runs from the tcon to the glass lcd panel. Some people have had limited success inserting foam to force a better contact, although this is at best a temporary patch.

                                      PlainBill
                                      So you don't think this is a problem with the T-CON board itself? I disassembled the TV all the way and removed the T-CON board and cleaned all of the contacts on both the board and on the 4 ribbon cables, and still no change. I already had the TV put back together before I saw your post so I didnt put any foam or anything inside there. Where would I place the foam at if I do decide to take it apart again? Would it go under the ribbon cables? or above the ribbon cables between the area where it connects into the lcd panel and the top of the housing?

                                      Comment


                                        #20
                                        Re: Sanyo DP46848 screen half dark

                                        Originally posted by CamBlack View Post
                                        So you don't think this is a problem with the T-CON board itself? I disassembled the TV all the way and removed the T-CON board and cleaned all of the contacts on both the board and on the 4 ribbon cables, and still no change. I already had the TV put back together before I saw your post so I didnt put any foam or anything inside there. Where would I place the foam at if I do decide to take it apart again? Would it go under the ribbon cables? or above the ribbon cables between the area where it connects into the lcd panel and the top of the housing?
                                        No, it's probably not the tcon. A pair of flex conductors run from the tcon to the LCD panel, the other end of those conductors are bonded to the glass plate that makes up the active part of an lcd panel. While it is possible the problem is the tcon, it is much more likely the bond between the flex conductor and the glass panel has broken. A definitive test would be to tap the tcon and then the upper left corner of the display to see which 'fixes' the problem.

                                        If it is the panel, you would have to put something between the panel housing and the panel frame, or inside the panel frame. Even then the cure is temporary at best.

                                        PlainBill
                                        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                                        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                                        Comment

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