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    Samsung LE40B620R3W shuts down

    Samsung LE40B620R3WQXU
    I'm thinking that the main board may be faulty, I would appreciate any help to test and fix it.
    The TV works for about 2 minutes and then shuts down with no standby light. When the main board is disconnected the back lights come on and the TV stays on until powered off.

    Voltages on power board

    Main board disconnected
    4.88
    4.88
    2.74
    12.07
    12.07
    0
    5.01
    5.01
    0
    0
    12.07
    0
    5.01
    0.76

    Main board connected
    4.88
    4.88
    2.74
    12.23
    12.23
    0
    4.95
    4.95
    0
    0
    12.23
    0
    4.95
    0.75

    #2
    Re: Samsung LE40B620R3W shuts down

    Is there a legend/label on the board describing the pins and the number of the pin?, you put the voltage but we have no way of knowing what it is, so you want to do like, pin 1: ps on 3.3 volts, pin 2 etc. etc.

    Comment


      #3
      Re: Samsung LE40B620R3W shuts down

      Post pictures of your power supply board and of the legend as nomoresonys suggests, What is the part number of the power supply BN44-xxxxxx?
      Willing to help but I'm no expert.

      Comment


        #4
        Re: Samsung LE40B620R3W shuts down



        Voltages on power board

        Main board disconnected
        pin 29 0
        pin 27 4.88
        pin 25 4.88
        pin 23 2.74
        pin 21 12.07
        pin 19 12.07
        pin 17 0
        pin 15 5.01
        pin 13 5.01
        pin 11 0
        pin 9 0
        pin 7 12.07
        pin 5 0
        pin 3 5.01
        pin 1 0.76

        Main board connected
        pin 29 0
        pin 27 2.68
        pin 25 1.79
        pin 23 2.74
        pin 21 12.23
        pin 19 12.23
        pin 17 0
        pin 15 4.95
        pin 13 4.95
        pin 11 0
        pin 9 0
        pin 7 12.23
        pin 5 0
        pin 3 4.95
        pin 1 0.76

        Attached Files

        Comment


          #5
          Re: Samsung LE40B620R3W shuts down

          Comment


            #6
            Re: Samsung LE40B620R3W shuts down

            Comment


              #7
              Re: Samsung LE40B620R3W shuts down

              Your photo is difficult to read. It would make easier reading to list them similar to below. Where are all the even number listings.ie pins 2, 4, 6 ....28
              Also what is the board number.
              Attached Files
              Last edited by dick_barton; 10-15-2020, 12:38 PM.
              Willing to help but I'm no expert.

              Comment


                #8
                Re: Samsung LE40B620R3W shuts down

                I think the mainboard isn't sending the proper signal/s.

                Comment


                  #9
                  Re: Samsung LE40B620R3W shuts down

                  https://www.badcaps.net/forum/attach...1&d=1602832478
                  Attached Files
                  Last edited by Ukdigger; 10-16-2020, 01:21 AM.

                  Comment


                    #10
                    Re: Samsung LE40B620R3W shuts down

                    The board number is BN44-00264A. I only tested the pins that had wires coming from them.

                    Comment


                      #11
                      Re: Samsung LE40B620R3W shuts down

                      Originally posted by Ukdigger View Post
                      The board number is BN44-00264A. I only tested the pins that had wires coming from them.
                      psu schematic
                      Attached Files

                      Comment


                        #12
                        Re: Samsung LE40B620R3W shuts down

                        Recheck pin 1, check it with everything hooked up, all boards connected, check in standby which is tv plugged into power but not turned on, which looks like you have .76 v, keeping probes in place hit power button on tv, see if that voltage changes, usually it should be around 3.3 steady v, when tv on and working properly.

                        Comment


                          #13
                          Re: Samsung LE40B620R3W shuts down

                          I did what you said and I get 0 volts in standby and when the power button is pressed it shoots up to 0.76 volts

                          Comment


                            #14
                            Re: Samsung LE40B620R3W shuts down

                            The ON/OFF is connected to the 5.3V Standby rail via RM882 so should be several volts when the mainboard is diconnected from the power supply.
                            I would measure the dc voltage on the 3 pins of QM802.
                            Willing to help but I'm no expert.

                            Comment


                              #15
                              Re: Samsung LE40B620R3W shuts down




                              As you look at my photo, I'm getting 0.06 volts of the left pin, 0 volts top right pin and 0.67 volts on the bottom right pin
                              Attached Files

                              Comment


                                #16
                                Re: Samsung LE40B620R3W shuts down

                                I think this is an always on power supply. If with the power supply disconnected from the mainboard you jumper a 1K resistor from ON/OFF to ground can you check that only the +5V stanby is running and the other supplies are off.

                                If this is the case then you probably do have a mainboard fault.
                                Last edited by dick_barton; 10-16-2020, 09:52 AM.
                                Willing to help but I'm no expert.

                                Comment


                                  #17
                                  Re: Samsung LE40B620R3W shuts down

                                  PS-ON of 0.76V is fine since the Base resistor RM864 is only 200 Ohms and RM882 pull-up is 10K.
                                  The circuit is working otherwise you will not have switched 13V right now.
                                  So the question is what are the Voltages at the connector when TV goes into shutdown after 2 minutes?
                                  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


                                    #18
                                    Re: Samsung LE40B620R3W shuts down

                                    Originally posted by budm View Post
                                    PS-ON of 0.76V is fine since the Base resistor RM864 is only 200 Ohms and RM882 pull-up is 10K.
                                    The circuit is working otherwise you will not have switched 13V right now.
                                    So the question is what are the Voltages at the connector when TV goes into shutdown after 2 minutes?
                                    Ok then, my bad.

                                    Comment


                                      #19
                                      Re: Samsung LE40B620R3W shuts down

                                      When using 1K resistor from ON/OFF to ground all other voltages were 0 volts, only +5V standby was on. The TV has been working normally now for about 30 minutes. When it goes off again I will test all the voltages and report back.

                                      Comment


                                        #20
                                        Re: Samsung LE40B620R3W shuts down

                                        TV was working normally until this morning and then went off with no standby light. Here are the voltages.

                                        https://www.badcaps.net/forum/attach...1&d=1603099828
                                        Attached Files

                                        Comment

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