Samsung UN48H6350AF Black Screen, No Sound

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  • mlemon
    Member
    • Feb 2021
    • 34
    • United States

    #1

    Samsung UN48H6350AF Black Screen, No Sound

    Issue with my TV:

    1. The standby red LED continuously flashing red with dark screen. Pressing the power button manually or from the remote has no effect
    2. When and if all the cables are connected, the display is dark, nothing appears on the screen.
    3. The flash light test of the LCD display does not produce any images that is because there is no power reaching the LCD from the Tcon board.
    4. The Tcon board gets no power at all on pins 47 to 51 (according to the legend) of flex cable from the MB, expected 12 to 13V. The fuse on the Tcon is NOT open, I verified. And there are 3 LEDs on the Tcon board, none is lit, supposedly blue. Again, the Tcon board does not get power from the MB board therefore, I do not expect these blue LEDs to light up.
    5. The Main logic board gets the 13VDC from the PS. I am very confident the PS has no issue given I verified all the voltages with and without load (cable to backlight LEDs and cable to to MB).
    6. If I disconnect the flex cable from MB to the Tcon board, the backlight LEDs start flickering at the same frequency as the flashing red light, appears that way anyway.
    7. If I disconnect the power cable from PS to the MB, the backlight LEDs will light up and say lit with Blue screen while the standby red light still flashing
    8. Disconnecting the speaker and power board/IR board from the PS has no effect.
    9. Here are the voltage readings on the PS plug to the MB:

    Again, pressing power button has no effect but the PS to MB makes a bit of a difference on some readings, the Even pins [2,4,6]:

    Connector CNM803 - PS <---> MB. All measured Voltages:

    (Even Pin#)

    All Cables connected PS <---> MB Disconnected

    2 OD/UD 0.1 - 2.47V 2.29V
    4 BLU ON/OFF 0.0 - 0.15V 3.3V
    6 PS ON/OFF 0.0 - 3.30V 4.46V
    8 GND 0.0 0.0
    10 GND 0.0 0.0

    (Odd Pin#) - same values when all cables connected and disconnected.

    1 A13V 12.12 - 12.77V
    3 A13V 12.1 - 12.77V
    5 A13 12.1 - 12.72
    7 A13V 12.1 - 12.72
    9 GND 0V

    My observation is that the CP or BGA on the MB keeps resetting probably on Pin 6 (PS ON/OFF). I did back trace pin 6 and 4 with some measurements on the MB but could not find anything shorted or open, at least nothing obvious. And nothing charred or burnt on any of the boards.
    Also, I heated the BGA with hot air gun for 3min and did not make any difference.

    All indications point to the MB but I am more interested in figuring out which component (s) is faulty. Replacing a whole board takes the fun out of it and frankly not worth the cost given how expensive they are. So any help or pointers much appreciated. Thanks
    Attached Files
    Last edited by mlemon; 05-06-2021, 09:01 PM. Reason: Edited the Title
  • mlemon
    Member
    • Feb 2021
    • 34
    • United States

    #2
    Re: Samsung UN48H6350AF Black Screen, No Sound

    PS: Plz ignore the "blue" LED on the Tcon. This is not my board. Ones on my board (3 LEDs), none light up due to NO power getting to the Tcon board. However, 2 out of the 3 LEDs do light up when I checked by Multimeter, the 3rd looks burnt out which should not effect the function of the board as it is just an indication LED.

    Comment

    • neilc6
      Badcaps Legend
      • Nov 2015
      • 1550
      • Canada

      #3
      Re: Samsung UN48H6350AF Black Screen, No Sound

      Tcon voltage typically comes from a power supply and is switched through a FET with a control signal from the processor on the main board. Either the control signal is not going high or the FET is bad. Usually a few pins on the outer side of the LVDS cable carries the voltage.

      Comment

      • mlemon
        Member
        • Feb 2021
        • 34
        • United States

        #4
        Re: Samsung UN48H6350AF Black Screen, No Sound

        Yes, the outer lines 47 to 51 on the LVDS suppose to carry that voltage from the MB to the Tcon but re not present. I will reinvestigate around those lines on the MB side for FET control signal or faulty one. Thanks for the reply

        Comment

        • mlemon
          Member
          • Feb 2021
          • 34
          • United States

          #5
          Re: Samsung UN48H6350AF Black Screen, No Sound

          However, the Tcon in my situation is probably secondary issue if any. The reason is that when the Tcon LVDS is completely disconnected, the TV still behaves the same; continuous flashing red and backlight LEDs flickering. Again pointing to the MB. Thanks

          Comment

          • mlemon
            Member
            • Feb 2021
            • 34
            • United States

            #6
            Re: Samsung UN48H6350AF Black Screen, No Sound

            Here is the LVDS image. Highlighted in yellow the power lines to the Tcon from MB.
            Attached Files

            Comment

            • mlemon
              Member
              • Feb 2021
              • 34
              • United States

              #7
              Re: Samsung UN48H6350AF Black Screen, No Sound

              I would like some help on identifying the specs on this component on the MB next to the LVDS; Q201_NHSP (DFPA15 written on it). It's a 6pin that looks like an IC but am suspecting it is a dual MOSFET. See attached image with red arrow showing location.
              I can't find any info on it online as I would like to replace it. I appreciate all the help.
              Attached Files

              Comment

              • mlemon
                Member
                • Feb 2021
                • 34
                • United States

                #8
                Re: Samsung UN48H6350AF, Standby Red Light Continuously Flashing, No Pic or Sound

                Originally posted by mlemon
                Issue with my TV:

                1. The standby red LED continuously flashing red with dark screen. Pressing the power button manually or from the remote has no effect
                2. When and if all the cables are connected, the display is dark, nothing appears on the screen.
                3. The flash light test of the LCD display does not produce any images that is because there is no power reaching the LCD from the Tcon board.
                4. The Tcon board gets no power at all on pins 47 to 51 (according to the legend) of flex cable from the MB, expected 12 to 13V. The fuse on the Tcon is NOT open, I verified. And there are 3 LEDs on the Tcon board, none is lit, supposedly blue. Again, the Tcon board does not get power from the MB board therefore, I do not expect these blue LEDs to light up.
                5. The Main logic board gets the 13VDC from the PS. I am very confident the PS has no issue given I verified all the voltages with and without load (cable to backlight LEDs and cable to to MB).
                6. If I disconnect the flex cable from MB to the Tcon board, the backlight LEDs start flickering at the same frequency as the flashing red light, appears that way anyway.
                7. If I disconnect the power cable from PS to the MB, the backlight LEDs will light up and say lit with Blue screen while the standby red light still flashing
                8. Disconnecting the speaker and power board/IR board from the PS has no effect.
                9. Here are the voltage readings on the PS plug to the MB:

                Again, pressing power button has no effect but the PS to MB makes a bit of a difference on some readings, the Even pins [2,4,6]:

                Connector CNM803 - PS <---> MB. All measured Voltages:

                (Even Pin#)

                All Cables connected PS <---> MB Disconnected

                2 OD/UD 0.1 - 2.47V 2.29V
                4 BLU ON/OFF 0.0 - 0.15V 3.3V
                6 PS ON/OFF 0.0 - 3.30V 4.46V
                8 GND 0.0 0.0
                10 GND 0.0 0.0

                (Odd Pin#) - same values when all cables connected and disconnected.

                1 A13V 12.12 - 12.77V
                3 A13V 12.1 - 12.77V
                5 A13 12.1 - 12.72
                7 A13V 12.1 - 12.72
                9 GND 0V

                My observation is that the CP or BGA on the MB keeps resetting probably on Pin 6 (PS ON/OFF). I did back trace pin 6 and 4 with some measurements on the MB but could not find anything shorted or open, at least nothing obvious. And nothing charred or burnt on any of the boards.
                Also, I heated the BGA with hot air gun for 3min and did not make any difference.

                All indications point to the MB resetting but I am more interested in figuring out which component (s) is faulty. Replacing a whole board takes the fun out of it and frankly not worth the cost given how expensive they are. So any help or pointers much appreciated. Thanks
                The tv looks its continously restting.

                Comment

                • mlemon
                  Member
                  • Feb 2021
                  • 34
                  • United States

                  #9
                  Re: Samsung UN48H6350AF Black Screen, No Sound

                  Finally fixed by replacing the MB as I could not source a major component that I am confident is the culprit, the CPU.

                  All the MB voltages read correctly however they kept resetting which after further investigation pointed to the CPU. I did try reflow the CPU using my Hot air station for nearly 8 min at 480C but did not help. I would have liked to replace the CPU but I could not find online.
                  So I ended up buying a brand new MB not exactly the same but it worked. This MB is same PCB layout but missing one USB and HDMI and couple of supporting components which I am thinking to source from the original defect MB. And at a cost of $35 compared to the original one which is very hard to find for $100 or more.
                  Additionally, the Tcon had bad LED2 which I managed to buy from surplus Excess Solution in San Jose, CA and fixed that.

                  Here is the MB I bought in eBay but picked up in person, very close to me so was great:
                  https://www.ebay.com/itm/28286238088...Cclp%3A2334524

                  Comment

                  • mlemon
                    Member
                    • Feb 2021
                    • 34
                    • United States

                    #10
                    Re: Samsung UN48H6350AF Black Screen, No Sound

                    Tcon tiny green LED is one I replaced. Original was blue I assume based on other two & from a pic I see elsewhere
                    Attached Files

                    Comment

                    • mlemon
                      Member
                      • Feb 2021
                      • 34
                      • United States

                      #11
                      Re: Samsung UN48H6350AF Black Screen, No Sound

                      And with new MB
                      Attached Files

                      Comment

                      • mlemon
                        Member
                        • Feb 2021
                        • 34
                        • United States

                        #12
                        Re: Samsung UN48H6350AF Black Screen, No Sound

                        Update: I was able to find a CPU but too late now

                        Comment

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