Samsung UN40H5203 Flashing Backlight

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  • jason123
    Badcaps Legend
    • Oct 2015
    • 1068
    • USA

    #1

    Samsung UN40H5203 Flashing Backlight

    Happy holidays folks.

    I just got this Samsung with weird symptom. Powers up and the backlight flashes very bright at roughly 1 Hz. When I first got it, it flashed few times then stopped. When I opened up the panel, the majority of the LEDs where dead. I replaced them all put it back together and it's flashing again. I don't want to troubleshoot while flashing because the LEDs are ultra bright and will eventually die.

    Seems that the LED drive circuit doesn't have sufficient current limit?

    It's BN44-00769C power board. Has anyone seen this before? The backlight voltage at pin with LEDs disconnected is roughly 200 V and doesn't fluctuate with the LEDs disconnected.
    Attached Files
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Samsung UN40H5203 Flashing Backlight

    1) You indicated that the old LED's were dead, were they shorted out or open circuit?
    2) What LED's did you use for the replacement, spec?
    3) lift up one leg of the diode d9801? (next to blue disc cap C9842) in the LED driver section then check the resistance between the two legs of that diode in both directions, report the result.
    4) The LED's are connected in series and the LED power supply rating (printed on the board) is 151.8V @425mA with load, so 200V without load is correct.
    5) Provide the P/N of the LED driver SMD IC9805 on the bottom side of the board by the LED connector.
    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

    • jason123
      Badcaps Legend
      • Oct 2015
      • 1068
      • USA

      #3
      Re: Samsung UN40H5203 Flashing Backlight

      Hi budm
      1) You indicated that the old LED's were dead, were they shorted out or open circuit?
      Recall upon first few power ups, these were flashing, then eventually stopped. 2 strips had many shorted. the 3rd strip has several open.

      2) What LED's did you use for the replacement, spec?
      I use the 1W 3V LEDs (I've used them before on Samsung, very similar to the ones that were on the board, physically)

      3) lift up one leg of the diode d9801? (next to blue disc cap C9842) in the LED driver section then check the resistance between the two legs of that diode in both directions, report the result.
      One direction shows open (High Impdeance) and the other direction 4.62 MOhm

      4) The LED's are connected in series and the LED power supply rating (printed on the board) is 151.8V @425mA with load, so 200V without load is correct.

      5) Provide the P/N of the LED driver SMD IC9805 on the bottom side of the board by the LED connector.
      Marking on the IC is 7014X

      Thanks

      Comment

      • jason123
        Badcaps Legend
        • Oct 2015
        • 1068
        • USA

        #4
        Re: Samsung UN40H5203 Flashing Backlight

        Anything else you can suggest looking into?

        Comment

        • vinceroger69
          Badcaps Legend
          • Mar 2012
          • 6714
          • uk

          #5
          Re: Samsung UN40H5203 Flashing Backlight

          maybe same as in this video disconnect pwm wire if your set is the same
          https://www.youtube.com/watch?v=sQn5QZ4SK80

          Comment

          • jason123
            Badcaps Legend
            • Oct 2015
            • 1068
            • USA

            #6
            Re: Samsung UN40H5203 Flashing Backlight

            Thanks. This TV is responsive to power button and the backlight flashes even if the main board is disconnected. I think it's LED strips or Power Supply. Maybe I used the 3V LEDs and I should have used the 6V instead?

            Comment

            • vinceroger69
              Badcaps Legend
              • Mar 2012
              • 6714
              • uk

              #7
              Re: Samsung UN40H5203 Flashing Backlight

              do samsung even use 6v leds i know lg do though whats the lcd panel number used in this set maybe then we can find the led specs
              Last edited by vinceroger69; 12-23-2018, 07:50 AM.

              Comment

              • jason123
                Badcaps Legend
                • Oct 2015
                • 1068
                • USA

                #8
                Re: Samsung UN40H5203 Flashing Backlight

                Here is the label on the panel.. not sure if it tells you the LED spec?
                Attached Files

                Comment

                • budm
                  Badcaps Legend
                  • Feb 2010
                  • 40746
                  • USA

                  #9
                  Re: Samsung UN40H5203 Flashing Backlight

                  Were these your LED strips with 38 LED's total?
                  http://www.silvershoptvparts.com/sam...r-un40h5203af/
                  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

                  • jason123
                    Badcaps Legend
                    • Oct 2015
                    • 1068
                    • USA

                    #10
                    Re: Samsung UN40H5203 Flashing Backlight

                    That's it eaxactly.. 12 leds center 13 top and 13 bottom.

                    Comment

                    • jason123
                      Badcaps Legend
                      • Oct 2015
                      • 1068
                      • USA

                      #11
                      Re: Samsung UN40H5203 Flashing Backlight

                      You think its the LEDs that are causing the problem? All have been replaced and all light up. Would love to get this repaird asap. I ordered a ps board.. waste of money?

                      Comment

                      • vinceroger69
                        Badcaps Legend
                        • Mar 2012
                        • 6714
                        • uk

                        #12
                        Re: Samsung UN40H5203 Flashing Backlight

                        3v leds would use 114v 6v leds 228v your power pcb states 151.8 v i hate issues with backlights i usually just replace the lot like you have and that fixes the issue maybe budm will have more ideas on what too check next
                        Last edited by vinceroger69; 12-24-2018, 10:22 AM.

                        Comment

                        • jason123
                          Badcaps Legend
                          • Oct 2015
                          • 1068
                          • USA

                          #13
                          Re: Samsung UN40H5203 Flashing Backlight

                          A new power supply board just arrived and it's doing exactly the same.. flashing backlight at 1 Hz or so... it's got to be the strings

                          Comment

                          • budm
                            Badcaps Legend
                            • Feb 2010
                            • 40746
                            • USA

                            #14
                            Re: Samsung UN40H5203 Flashing Backlight

                            Sounds like you have to get the LED strips out and wire them up out side the panel and hook up to the power supply board and see what is going on.
                            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

                            • jason123
                              Badcaps Legend
                              • Oct 2015
                              • 1068
                              • USA

                              #15
                              Re: Samsung UN40H5203 Flashing Backlight

                              Just a quick update.. got a set of backlights from China ($38.00 + a couple of weeks) and it fired right up. All is good.. thank you

                              Comment

                              • nomoresonys
                                Badcaps Legend
                                • Jan 2013
                                • 12145
                                • U.S.

                                #16
                                Re: Samsung UN40H5203 Flashing Backlight

                                So the first set of backlights you replaced were bad, were they new, if so could you share where you got them? wouldn't want to buy from them if they sell bad lights.
                                Last edited by nomoresonys; 01-08-2019, 07:16 PM.

                                Comment

                                • jason123
                                  Badcaps Legend
                                  • Oct 2015
                                  • 1068
                                  • USA

                                  #17
                                  Re: Samsung UN40H5203 Flashing Backlight

                                  No, the first set I installed where the original but with LEDs replaced.. They worked great outside the set with a tester.. so I'm not sure what was wrong with them.

                                  Comment

                                  • nomoresonys
                                    Badcaps Legend
                                    • Jan 2013
                                    • 12145
                                    • U.S.

                                    #18
                                    Re: Samsung UN40H5203 Flashing Backlight

                                    Ok, I see, thanks, nice fix.

                                    Comment

                                    • budm
                                      Badcaps Legend
                                      • Feb 2010
                                      • 40746
                                      • USA

                                      #19
                                      Re: Samsung UN40H5203 Flashing Backlight

                                      May be you should try out the old set of LED powered by your power supply/LED driver board so you can see what is going on.
                                      LED tester only puts out 30mA so any bad connection, weak LED may not show problem until they driven by high current.
                                      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

                                      • jason123
                                        Badcaps Legend
                                        • Oct 2015
                                        • 1068
                                        • USA

                                        #20
                                        Re: Samsung UN40H5203 Flashing Backlight

                                        So my first step was to replace LEDS. Once i did, i tested with original power supply. They turned on blinking very bright. Got a new ps board. It did the same thing but i left the strings connected too ling while i was attempting to take measurements... eventually most leds shorted opened again...unfortunately unsalvageable at this point .. none related quick opinion.. up for sale for $20 is a samsung 50" 4k tv... any guess if this issue is fixable (color line and color bleeding on top)

                                        Comment

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