Samsung LN40B630N1F PSU Problem

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  • landyboy
    Badcaps Veteran
    • Apr 2013
    • 443
    • USA

    #1

    Samsung LN40B630N1F PSU Problem

    I just picked up a Samsung LN40B630N1F that will not power up no lights on the front at all. When I opened it I found the fuse noted below in the picture blown. I replaced the fuse and as soon as I put AC power to the board the fuse blew again. I thin pulled the board out of the inverter sockets and disconnected it from the main board put AC to it and the fuse blew again. With the fuse removed I have around 160vdc volts across the fuse sockets and about 33vdc to ground both sides.
    Attached Files
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: Samsung LN40B630N1F PSU Problem

    Schematic
    http://www.tgohome.com/ServiceManual...&Search=Submit

    Test bridge, diodes, fets, etc.
    Last edited by tom66; 07-21-2013, 02:40 PM.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

    Comment

    • landyboy
      Badcaps Veteran
      • Apr 2013
      • 443
      • USA

      #3
      Re: Samsung LN40B630N1F PSU Problem

      QI820
      50 ohms 50 ohms .3 ohms

      QI821
      39 39 .3

      Comment

      • tom66
        EVs Rule
        • Apr 2011
        • 32560
        • UK

        #4
        Re: Samsung LN40B630N1F PSU Problem

        It's dead, Jim... You'll likely have to replace a few resistors and diodes around them, but it's transformer isolated so the controller IC should be OK.
        Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
        For service manual, schematic, boardview (board view), datasheet, cad - use our search.

        Comment

        • landyboy
          Badcaps Veteran
          • Apr 2013
          • 443
          • USA

          #5
          Re: Samsung LN40B630N1F PSU Problem

          I also tested the Bridge Rectifier

          neg lead to pos lug pos lead to ac lugs 1600ohms
          same with pos lead on neg lug and neg lead to ac

          Comment

          • landyboy
            Badcaps Veteran
            • Apr 2013
            • 443
            • USA

            #6
            Re: Samsung LN40B630N1F PSU Problem

            What readings should I see on those two?

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: Samsung LN40B630N1F PSU Problem

              Expected for FET: Open all directions except 2-3 or 2-1 where one diode may be visible in reverse.
              Test bridge out of circuit to check it.
              Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
              For service manual, schematic, boardview (board view), datasheet, cad - use our search.

              Comment

              • landyboy
                Badcaps Veteran
                • Apr 2013
                • 443
                • USA

                #8
                Re: Samsung LN40B630N1F PSU Problem

                I found these do you think they are acceptable?
                FDPF 7N50 ( 7 AMP) MOSFET UPGRADE FOR FDPF 7N50U (5AMP) MOSFET

                Comment

                • tom66
                  EVs Rule
                  • Apr 2011
                  • 32560
                  • UK

                  #9
                  Re: Samsung LN40B630N1F PSU Problem

                  Should be OK.
                  Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                  For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                  Comment

                  • landyboy
                    Badcaps Veteran
                    • Apr 2013
                    • 443
                    • USA

                    #10
                    Re: Samsung LN40B630N1F PSU Problem

                    UPDATE: Replace the two above mentioned FETS and set is working great!!

                    Comment

                    • tom66
                      EVs Rule
                      • Apr 2011
                      • 32560
                      • UK

                      #11
                      Re: Samsung LN40B630N1F PSU Problem

                      Nice one! Thanks for feedback.
                      Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                      For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                      Comment

                      • ajimetro
                        New Member
                        • Aug 2013
                        • 6
                        • Colombo

                        #12
                        Re: Samsung LN40B630N1F PSU Problem

                        I had same kind of issue in Toshiba 40AV700E LCD TV.Two FETs are burnt (7N50U) & i could find the FET of 7N50 (not the 7N50U) in my country.So I replaced the two FET s & also Smoothing cap 1000uF/10V are Leak.Then replaced it also
                        & power up the TV Using 100W bulb replaced with main Fuse.
                        Its blinks with bright.Then i replaced the fuse & power up.It works for about 30 seconds & burnt the FETs again.Not only that near SMD resistors & Diode are also burnt.Now I couldnt find the values for SMD s.So how may I find the values for that & may i replace the 7N50U with 7N50?

                        Thanks.

                        Comment

                        • DV442
                          New Member
                          • May 2014
                          • 2
                          • USA

                          #13
                          Re: Samsung LN40B630N1F PSU Problem

                          Originally posted by tom66
                          It's dead, Jim... You'll likely have to replace a few resistors and diodes around them, but it's transformer isolated so the controller IC should be OK.
                          What should the readings be at Q1820 and Q1821?

                          Comment

                          • tom66
                            EVs Rule
                            • Apr 2011
                            • 32560
                            • UK

                            #14
                            Re: Samsung LN40B630N1F PSU Problem

                            Nearly open circuit all but one way around.
                            Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                            For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                            Comment

                            • DV442
                              New Member
                              • May 2014
                              • 2
                              • USA

                              #15
                              Re: Samsung LN40B630N1F PSU Problem

                              Hmm, thanks for the info.

                              It appears that Q1821 is good. But on Q1820 I have readings that are not the same.


                              Q1821
                              Pin 1 - Pin 2= .4 ohms
                              Pin 1 - Pin 3= 1.0 ohms
                              Pin 2 - Pin 3= 1.1 ohms


                              Q1820
                              Pin 1 - Pin 2= .3 ohms
                              Pin 1 - Pin 3= 32.3 ohms
                              Pin 2 - Pin 3= 32.3 ohms

                              Would you say that Q1820 is bad? Thanks for your help!

                              Comment

                              • rawilson3
                                Idea Pimp
                                • Jul 2014
                                • 12
                                • USA

                                #16
                                Re: Samsung LN40B630N1F PSU Problem

                                I am having the exact same issue and the same fuse is blown. Is there a diagram that shows the components tested and expected test values that I could follow to diagnose and repair my set? Thanks for your time and help.
                                It does not take all kinds, but you get them.

                                Comment

                                • budm
                                  Badcaps Legend
                                  • Feb 2010
                                  • 40746
                                  • USA

                                  #17
                                  Re: Samsung LN40B630N1F PSU Problem

                                  Is your board # is BN44-00264A? If it is then take the resistance readings as shown in post 3~10 and report the readings.
                                  Attached Files
                                  Last edited by budm; 10-13-2014, 09:07 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

                                  • rawilson3
                                    Idea Pimp
                                    • Jul 2014
                                    • 12
                                    • USA

                                    #18
                                    Re: Samsung LN40B630N1F PSU Problem

                                    Thanks for the reply. I will double check the model of the board and test if applicable tonight and followup with results.

                                    Thanks!
                                    It does not take all kinds, but you get them.

                                    Comment

                                    • rawilson3
                                      Idea Pimp
                                      • Jul 2014
                                      • 12
                                      • USA

                                      #19
                                      Re: Samsung LN40B630N1F PSU Problem

                                      ok

                                      Q1820

                                      1-2 : 2.6
                                      2-3: 2.0
                                      1-3: 2.6

                                      Q1821

                                      1-2: 1.9
                                      2-3: 1.9
                                      1-3: 2.6
                                      It does not take all kinds, but you get them.

                                      Comment

                                      • rawilson3
                                        Idea Pimp
                                        • Jul 2014
                                        • 12
                                        • USA

                                        #20
                                        Re: Samsung LN40B630N1F PSU Problem

                                        Any ideas if my parts are dead? Should I take any additional readings?

                                        Thanks!
                                        It does not take all kinds, but you get them.

                                        Comment

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