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    Samsung UN65JS9500 / BN44-00818A - no LED backlight

    Hi Everyone,

    I've been poking though the forum and have got a lot of great info so far but I'm at a loss at this point and was turning to the forum for some assistance.

    I have been troubleshooting my UN65JS9500 TV where there is no backlight. Upon further investigation of the Power Supply / LED Board BN44-00818A when testing the CN803 connector(circled in green) which goes to the LED control board I have Pin 1 - 5v and Pin 3 -13V but I would expect to see 32V on PIN 14 - PIN 21, there is no voltage.

    I have continued to investigate and found no voltage at TM901CS (circled in pink) which I believe is responsible for generating the 32V for the Vdrv outputs but I also haven't located the schematic for this board either.

    If I look at the board correctly there is a THICK black line which I believe depicts AC vs DC. ie DC in the upper left if looking at the top of the board and everything else is AC.

    I found FP903S (Circled in red) to be faulty and replaced it however when the board was powered on the fuse blew. The fuse I replaced it with was Schurter Inc. / 0001.2509.PT which is a 3.15A Slow Blow 250V fuse.

    If I trace back from FP903S I come to the middle leg of DP807C(circled in blue). Does anyone know what the voltage output and current should be? Or have a datasheet for SFI608PT or is it SF1608PT?

    I've attached high res photos from shopjimmy to help with the identification. Any guidance would be appreciated.
    Attached Files

    #2
    Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

    1) In the beginning, did you verify that the control Voltages are present or not? The switched power supply section will not be present until the control Voltages from Main board is present.
    2) That blown fuse is for just that switching power supply section that you circle, since the fuse is blown then you need to test the two power MOSFET for shorts.
    3) What s the P/N of the TM901CS?
    4) The DIODE DP801C and the two MOSFET QPxxx are for the PFC Voltage booster circuit. Do not touch that for now. The boosted Voltage should be around 380 ~ 400VDC (measured between the two legs of the main filter caps) which will be present when PS-ON control signal is present. 'P' for the part designator, I.E. DPxxx, is for indicating that part is used in the PFC circuit.
    5) The thick line is for showing the separation between the HOT deadly side and the Cold side of the circuit. The ground ref. for the meter when making Voltage measurement in the HOT side is the negative pin of the main filter cap, not chassis or the cold ground.
    6) The pins of the connector are labeled so when you report the readings you must put down the pin name and follow by the Voltage readings so we can easily see what it has or does not have.
    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: Samsung UN65JS9500 / BN44-00818A - no LED backlight

      Hi,

      1. I did not verify that there were control voltages in the beginning.
      2. The 2 power mosfets your refering to are QM901CS and QM902CS?
      3. LPF5L-5LM2
      4. The main filter caps are the 3 82uF caps? 396 VDC is the reading im getting but thats still concerning becase the fuse label on the board is 250V T3.15AH which is connected to the + of the caps

      Comment


        #4
        Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

        Originally posted by silentkav View Post
        Hi,

        1. I did not verify that there were control voltages in the beginning.
        2. The 2 power mosfets your refering to are QM901CS and QM902CS?
        3. LPF5L-5LM2
        4. The main filter caps are the 3 82uF caps? 396 VDC is the reading im getting but thats still concerning becase the fuse label on the board is 250V T3.15AH which is connected to the + of the caps
        2) Yes.
        3) Sorry, miscommunication, LPF5L-5LM2 is the power transformer, not the SMD 8-pin IC that drives the two MOSFET's.
        4) Main filter caps are CP803, 804, 805 connected in parallel. Tha blown fuse is for supply in the Voltage just for the switching power supply generated by QM801, 802. If the MOSFET's shorted out then it will blow that fuse FP903 which supplies the PFC boosted Voltage to just that section..

        BTW, we also need good clear pictures of the whole backside of the TV showing all the boards.

        "but I would expect to see 32V on PIN 14 - PIN 21, there is no voltage."
        Where did you see the 32V label for the CN803 connector?
        https://www.shopjimmy.com/samsung-bn...led-board.htm#
        Last edited by budm; 03-11-2020, 10:46 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


          #5
          Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

          Thanks for the information @budm

          I will focus on QM901CS and QM902CS for shorts and get back to you once they have been removed from the board.

          I will also get the PN of the SMD 8-pin IC which drives the 2 MOSFETs

          I will get clear pictures of the back of the TV showing the 4 boards.

          On the CN803 connector PIN14 - PIN21 are labeled as Vdrv and when you look at the far right middle it defines the voltage of the Vdrv as 30V(sorry misquoted 32V).

          In addition to this I got info from the following 2 videos on youtube:

          https://www.youtube.com/watch?v=mPkG-43RlXw

          and

          https://www.youtube.com/watch?v=PuOZ1TM1P5k

          Comment


            #6
            Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

            The IC is a 3110A

            Comment


              #7
              Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

              Attaching pictures
              Attached Files

              Comment


                #8
                Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                BTW, you do have experience replacing SMD component, right?
                The IC that drives the MOSFET's may be damaged when the MOSFET's shorted out, as you see in the Video he replaced only the MOSFET's but it still blows the fuse due to the damaged IC that causes new MOSFET's to blow.
                Last edited by budm; 03-12-2020, 09:18 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


                  #9
                  Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                  Small update...

                  I removed both MOSFETs (QM901CS / QM902CS) from the board and both appear to be shorted. I will do some additional testing tonight. I have replaced a number of onboard ICs in the past so that will not be a problem. Are there any other components I should be focusing on at this point or just those 2 MOSFETs and the IC?

                  Comment


                    #10
                    Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                    You need to test the components connected to the Gate of the MOSFET for damages, check the MOSFET's Source resistors if they use them.
                    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


                      #11
                      Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                      Long wait time for the mosfets. First order never arrived second just arrived.

                      I replaced both mosfets and the controller ic. I still do not have voltage out at CN803

                      Comment


                        #12
                        Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                        Originally posted by silentkav View Post
                        Long wait time for the mosfets. First order never arrived second just arrived.

                        I replaced both mosfets and the controller ic. I still do not have voltage out at CN803
                        Read my post #8 and #10.
                        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


                          #13
                          Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                          Originally posted by budm View Post
                          Read my post #8 and #10.
                          In regards to post #8

                          Since replacing the 2 MOSFETS and the IC the fuse does not blow.

                          For #10, I will go back though the test sequences. but from the large capacitors though the fuse that was blowing, its goes direct into the source leg of the MOSFETS which I just replaced.

                          Comment


                            #14
                            Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                            Me Again

                            After further testing, I powered everything back up and went back to the CN803 connector which is cabled to the LED control board.

                            Here are the voltages:

                            Pin 1 - 5v
                            Pin 3 - 13v
                            Pin 13 - 22 - 1.82v

                            Pin 13 - 22 is defined as the Vdrv which is suggested should be 30v

                            Tracing these pins back to the LPF5L-5LM2 power transformer which is fed from the 2 K15A50D. These are the 2 which were recently replaced along with the IC. Prior to the replacement the fuse feeding these would blow.

                            Do we know what the source voltage should be from the MOSFETS to the Transformer?

                            The main fuse from the capacitor bank is shows 397v but the source on the upper most MOSFET is only registering 122mV
                            Last edited by silentkav; 07-16-2020, 11:43 AM. Reason: update to my post regarding coltages

                            Comment


                              #15
                              Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                              https://www.badcaps.net/forum/attach...9&d=1583956774
                              As you can see, the upper MOSFET Drain (center pin) is connected to the fuse so you should have 397V to that Drain pin.
                              Attached Files
                              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


                                #16
                                Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                                My post #10:
                                "You need to test the components connected to the Gate of the MOSFET for damages, check the MOSFET's Source resistors if they use them."
                                Did you check those parts connected to the Gate of the MOSFETS?
                                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


                                  #17
                                  Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                                  Hi, too bad this thread didn't get followed up till the solution was found. I recently was given this same model tv with what appears to be the same issue.

                                  As Bud suggested I checked the gate drive resistors and they look to be blown. When I used to work on power supplies this usually meant the controller IC also is suspect. However, I cannot read the markings on this chip. it looks like it may say "3110" or maybe "8110"? Do these designs tend to use certain chips that might narrow this down?

                                  Thanks

                                  Comment


                                    #18
                                    Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                                    Still unresolved

                                    Work priorities come before fixing a TV.

                                    They are 3110A assuming we are talking about the same component. Required magnifier and a good light to identify.

                                    Comment


                                      #19
                                      Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                                      its the IC in position ICM901. It is also used in ICM801. Have you been able to find the replacement IC for that controller?

                                      RM911, 912 are the 100 ohm gate drive resistors that are probably damaged as they read about 1ohm in circuit. I haven't removed anything components yet.

                                      Comment


                                        #20
                                        Re: Samsung UN65JS9500 / BN44-00818A - no LED backlight

                                        looks like this could be the IC https://cdn.badcaps-static.com/pdfs/...0fed53a49c.pdf

                                        Comment

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