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    TV LEDS come on a brief second, then off

    Sony KDL60NX720 when turned on had a dark spot on top of the screen, then would turn off and blink red light 4 times

    Bad LED strip? That's what I thought. Took apart. It has 4 LED cables plugging into the LED board, I was going to swap two cables to confirm but I could not get the cables off

    Then decided to take two led strips off the front and swap the connections at the other end but they do not have connectors, they are ribbon connected

    Before I took it apart it would come on a few seconds then turn off, had a dark spot

    When I powered it up when first disassembled it showed the same issue but I had the press the power button a few times, each time I did I would see the bottom leds dimly light for a nano second then go off, then the third press of the power button the LEDs came on for a second, except the dark spot, then turned off (the dim area was part of a strip not all of it, I see no brown spots on the LEDs)

    Now when I do the same test, the first two times the leds on bottom dim for a nano second, then on the third try ALL (even the dark area) the leds come on for a nano second then turn off. When they all came on except the dark spot they were on a good 2 seconds, now when the ALL fire they last a nano second then turn off.

    I have to unplug the power each time to get it to work again.

    Is this the LED driver board the 4 leds wires go to or the board below (tcon I believe) that has a ribbon from the LED board going to it, then two ribbons out of the bottom of it to the LED screen?

    Thanks
    Last edited by kneeman; 08-16-2015, 10:39 PM.

    #2
    Re: TV LEDS come on a brief second, then off

    Any good clear pictures so we can see what we are dealing with?
    'then the third press of the power button they came on for a second, except the dark spot,' What do you mean by dark spot? Do mean that NOT ALL the LEDs light up?
    Do ALL the LEDs lights up with the same brightness?
    'When I powered it up when first disassembled ' Do you mean you took the LCD panel apart so you can see all the LEDs?
    Last edited by budm; 08-16-2015, 10:33 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


      #3
      Re: TV LEDS come on a brief second, then off

      Yes I have it all apart now.

      I powered it now and after the 2nd or 3rd press of the power button all the LEDs flicker on one time only, then turn off. I do not have the front LED connected to see if I get the 4 red lights, I can go check if I need to. That as what it did before I took it apart.

      When I first took it apart and powered it on, after pressing the power button three times, I would get the same results as I did before I took it apart. All the lights except part of one strip came on for a couple seconds then turned off.

      So when the problem first happened, the lights would come on longer than they do now, now they just blink once, BUT now they all blink, before part of one LED strip would not light,.

      The lit LEDS are all the same brightness when on.

      When it tried to fire up the first couple times I see the bottom leds very faintly flicker, then the turn on the third time I press power.
      Last edited by kneeman; 08-16-2015, 11:42 PM.

      Comment


        #4
        Re: TV LEDS come on a brief second, then off

        I'll photo whatever you want to see

        Comment


          #5
          Re: TV LEDS come on a brief second, then off

          btw, thanks for the tab fix issue, I posted photos over there of what I did on mine.
          Last edited by kneeman; 08-16-2015, 11:42 PM.

          Comment


            #6
            Re: TV LEDS come on a brief second, then off

            Sorry, the board that drives the screen at the bottom is covered by the stand it is currently on.
            The picture has never been a problem though just the backlight.
            Attached Files
            Last edited by kneeman; 08-16-2015, 11:13 PM.

            Comment


              #7
              Re: TV LEDS come on a brief second, then off

              On the secondary power supply I would suggest.

              Grounding BL_ERROR signal wire off of the connector cable.

              This will bypass the error signal
              And see how the picture is displayed.
              Will instantly show which is the offending led if you have and issue with it.

              It should be marked on the board BL_ERR I think.
              Just double check on the scematic and report back.

              etc..

              Comment


                #8
                Re: TV LEDS come on a brief second, then off

                the connector I have cricled should be it ..
                Attached Files

                Comment


                  #9
                  Re: TV LEDS come on a brief second, then off

                  I see the bl_err wire on the connector you circled.

                  To confirm. You want me to jump a wire from this connector while it is still connected, correct?

                  Or do I disconnect it and then jump a wire from the wire connector to the TV frame?

                  The same bl_err connector is on the main power supply board also. That wire connects them together.

                  Comment


                    #10
                    Re: TV LEDS come on a brief second, then off

                    Disconect and ground it
                    Removed it from the connector plug where I have cricled.

                    And tape it to the back of the metal chasis and that will ground it.

                    Comment


                      #11
                      Re: TV LEDS come on a brief second, then off

                      I pulled out the bl_err wire from the connector you have circled, the one on the smaller power supply and taped it to the back of the tv metal frame

                      Nothing changed.

                      Press power and nothing
                      Press power again and the leds faintly light a nano second
                      Press power again and the leds (all of them) light 100% bright for a flicker then off
                      Press power again and nothing

                      I assume that grounded it. There is a black and white wire that appear to be screwed to the frame the way it was built, they come off a small circuit board that comes of the board that has the HDMI, etc connectors. Not saying this is wrong just stating what other wires are screwed to the frame.

                      Anyone has any ideas what I need to replace?
                      Attached Files
                      Last edited by kneeman; 08-18-2015, 10:54 PM.

                      Comment


                        #12
                        Re: TV LEDS come on a brief second, then off

                        Just to confirm hae you tested all the individual leds ?

                        I mean individually with a multimeter.

                        You only really have 3 parts

                        the leds
                        the led driver board
                        the sub power supply board

                        ( or in some cases the wiring)


                        generally 1 of those is suspect...

                        Comment


                          #13
                          Re: TV LEDS come on a brief second, then off

                          How would I test the LEDS?

                          My I thought for sure since only half of one strip lit that it had a bad strip but I didn't see any burned ones. It has 4 strips so my plan was to unclip two from the led board and swap wires then see if the same strip only partially lit but I cold not see how this one clip comes off. It doesn't appear to slide or flip up. I tried to gently wiggle it back it is really on there tight.

                          I have a meter, how would I test each strip? The connection between the led strip and wire on the other end does not look removable, it looks like the connection between the lcd screen tabs and the circuit board.

                          btw, thanks for the responses Zomi and Bub
                          Attached Files
                          Last edited by kneeman; 08-19-2015, 06:34 AM.

                          Comment


                            #14
                            Re: TV LEDS come on a brief second, then off

                            Did I stump Zomi and/or Bud?

                            Anyone know what it is?

                            Comment


                              #15
                              Re: TV LEDS come on a brief second, then off

                              budm may be offline for a while
                              https://www.badcaps.net/forum/showthread.php?t=48410
                              regarding testing the leds/removing the clip i havnt really tested any myself as yet but im sure a more experienced member will advise when they have a few spare minutes.

                              Comment


                                #16
                                Re: TV LEDS come on a brief second, then off

                                Multi meter
                                Sharp probes
                                diode mode
                                will only light up one way
                                Test each led like a diode.
                                You have to make sure you contact the solder points to get a proper reading
                                Scratching area sometimes helps either side of the led.
                                tedious task ...

                                Or if you have acess to an inverter supply power then up as is..

                                ** that clip the black portion of it prys up to open it
                                gently work your fingernail across the entire length of it and it will come up.


                                Even if a few leds were out, Bypasssing the error wire should have bought the tv on

                                When you say nothing happened is the tv on ?
                                Do you have sound ?

                                Comment


                                  #17
                                  Re: TV LEDS come on a brief second, then off

                                  When together you could tell some leds on top were out when you turned the tv on, the tv would power off after a few seconds and flash the red led light four times. I only had to press the power button once to get it to turn on. After the red leds blinked it would not turn on and I would need to unplug it and plug it back in to be able to do the same test and results over and over.

                                  When first disassembled, I got the same results, tv would cut off after the leds came on a second (same area was dark on top, it was about half of one led strip) The only thing different than when assembled was I would press the power button once and nothing happened, I pressed again and the leds would dimmly glow (not fully light) a nano second, I press a third time and the leds would light at full brightness (except the ones that were out before.

                                  I didn't do any further disassembly (nothing left to take apart) all that I could have done was wiggle the power supply board or the led board while looking for loose connections etc but now when I press the power button nothing still happens the first time, then on the second press the leds still dimmly glow a nano second, when I press the third time ALL (even the ones that were out on top) turn on full bright but just a second, then the set turns off again and I have to umplug it to do the same test again.

                                  Sometimes now they light on the second press of the tv power button instead of the third press, but the first press of the power button never turns it on. I tried plugging the power in and waiting a minute before pressing power, same results.

                                  I have never tested diodes, I found a link on fluke training website so I will watch it and try and do what you are asking.

                                  2 weeks to football so I hope I can get this back up.

                                  Thanks If you/anyone has any other ideas let me know.

                                  Sorry to hear about Bud

                                  Comment


                                    #18
                                    Re: TV LEDS come on a brief second, then off

                                    You simply put the meter in diode mode/ conintuity mode
                                    then test the individual leds..
                                    they will only light up one way, go through them all
                                    mark dead ones..
                                    then you either source complete strips if you can
                                    find a donor strip from sony tv and replace individual leds.
                                    will need to be done with hot air

                                    Comment


                                      #19
                                      Re: TV LEDS come on a brief second, then off

                                      I'm confused. Have you actually removed the lcd panel to gain access to the led strips ?

                                      Comment


                                        #20
                                        Re: TV LEDS come on a brief second, then off

                                        Originally posted by mmartell View Post
                                        I'm confused. Have you actually removed the lcd panel to gain access to the led strips ?
                                        Yes it is apart. The LED strips must be taped on in addition to the three screws per strip because they will not budge after I took the screws out.

                                        So I need to find a way to get the LED strips off the silver metal bracket they are on and test the back side of the strip for each LED light where the connections are? So I do not need to remove the 4 clips the 4 LED strips attach to the LED board?

                                        I'm doing all this this afternoon.

                                        If I have to remove the LED strips any idea how they come off? They don't slide and I don't see any two tape just the screws.

                                        Thanks.
                                        Attached Files
                                        Last edited by kneeman; 08-22-2015, 10:16 AM.

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