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    Samsung LE37B550A5W Dead

    Hi All

    I have a Sammy that is dead, I am getting no voltage on the 30pin connector..more importantly no 5v from pin 27, I am getting 330v at smoothing cap, all usual suspects all ok, both internal fuses are ok, fets are ok, solder joints seem fine.

    No backlight flash with main disconnected

    It wont let me attach pics..maybe because I am a noob (managed to sort it)..if you need me to uplad better pics lt me know

    Anyone give us any pointers please
    Attached Files
    Last edited by signup; 05-06-2013, 10:18 AM.

    #2
    Re: Samsung LE37B550A5W Dead

    Can you please post good clear pictures of the board? I cannot read the P/N on that power supply board. Is it BN44-XXXXX?
    It is hard for us the troubleshoot the board whe we cannot clearly see the components and traces of the boards.
    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 LE37B550A5W Dead

      I'm pretty sure you can attach pics even if you only have one post. Click the "Go Advanced" button and see if a "Manage attachments" button is there.

      Comment


        #4
        Re: Samsung LE37B550A5W Dead

        Sorry crap camera...these might be better, pn bn44-00262a
        Attached Files

        Comment


          #5
          Re: Samsung LE37B550A5W Dead

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


            #6
            Re: Samsung LE37B550A5W Dead

            Here is the bulletin for the BN44-00262A and the diagram from TOM66 web site.
            Hi tom, do you want to upload the bulletin to your site?
            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


              #7
              Re: Samsung LE37B550A5W Dead

              Thanks for the schematic, the diode mentioned in the bulletin this reads ok in and out of board...do I change it anyway...I dont think the problems lies here though..but will change if needed

              I think I need to get the 5v back first

              Cheers

              Comment


                #8
                Re: Samsung LE37B550A5W Dead

                Yes we need to troubleshoot the 5V section first.
                See the diagram I posted.
                Check the snubber diode, DP801.
                Check the voltage on the two legs of capacitor CM804.
                Check the resistance of the IC UM801S (STR-W6252, TV unplugged) between Ground pin5 aginst all other pins.
                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 LE37B550A5W Dead

                  Originally posted by budm View Post
                  Check the snubber diode, DP801.
                  DP801..I cant find it, I can see dm801 sat next to cm804

                  CHeers

                  Comment


                    #10
                    Re: Samsung LE37B550A5W Dead

                    It should be close to the 5v stby transformer TM801S, the Cathode of th at DP801 is connected to RM811 and CM805 per diagram.
                    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 LE37B550A5W Dead

                      Sorry the only diode I can see by tranny is DP810...will come back to that

                      CM804 Voltage = 0.0v

                      Pin 1= No reading
                      pin2=1.1Mohms
                      pin3= No reading
                      pin4=1.1Mohms
                      Pin6=No reading

                      Comment


                        #12
                        Re: Samsung LE37B550A5W Dead

                        Originally posted by budm View Post
                        It should be close to the 5v stby transformer TM801S, the Cathode of th at DP801 is connected to RM811 and CM805 per diagram.
                        DM801 is connected to Rm811 and cm805 on the board..DM801 reads ok

                        Comment


                          #13
                          Re: Samsung LE37B550A5W Dead

                          I have just replaced UM801S with a STR-W6253 and now the voltage at CM804 is 130v

                          Edit still 0v at pin 27
                          Last edited by signup; 05-06-2013, 01:25 PM.

                          Comment


                            #14
                            Re: Samsung LE37B550A5W Dead

                            It sounds like you are not using the correct ground ref for the primary (hot) side of the circuit ofr taking the voltage readings on the primary side. The negative leg of the large 450vdc cap is the ground ref point for the primary circuits, do not use chassis as the ground ref point. The chassis is the ground point for the secondary (cold) side of the circuits.
                            I expect the DC voltage to be around 20vdc, you can measure right at the two legs of the CM804. IF you do have voltage there on CM804, that means the 5V STBY is working.
                            The 5V (STB_5.2V) STBY is at pin 3 of CNM802 is an always on power supply. The 5.3V (pin 13 ~16) and the 12V (pin 19) are switched on when main board sends the signal (PWR_ON/OFF) to PIN1 (>3VDC ref to chassis ground since this is the cold side of the circuits)) to turn on the 5.3V and the 12V power suuply.
                            Last edited by budm; 05-06-2013, 01:41 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


                              #15
                              Re: Samsung LE37B550A5W Dead

                              Ok thanks

                              Pin3 = 0v

                              CM804 = 0.04v

                              Comment


                                #16
                                Re: Samsung LE37B550A5W Dead

                                From your post 11:
                                "Pin 1= No reading
                                pin2=1.1Mohms
                                pin3= No reading
                                pin4=1.1Mohms
                                Pin6=No reading"

                                Pin 3 is the Source pin of the power MOSFET inside the UM801S which is connected toground through the Source resistor RM869 (0.3 Ohm). Check the resistance reading of that resistor.
                                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 LE37B550A5W Dead

                                  I am getting 0.3ohms there

                                  Comment


                                    #18
                                    Re: Samsung LE37B550A5W Dead

                                    Something isn't right with your measurement on pin 3 then, or the device isn't soldered to the board properly.
                                    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


                                      #19
                                      Re: Samsung LE37B550A5W Dead

                                      I have not got any voltages on any pin on the connector...before and after me changing UM801S.

                                      I dont know if it makes any difference to your train of thought but the cause of the failure was a power surge..the tv wouldnt work after a power cut

                                      Comment


                                        #20
                                        Re: Samsung LE37B550A5W Dead

                                        Well , that is an important info to know.
                                        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

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