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    Samsung UN58J5190AFXZA pwr supply troubleshooting help

    Set stopped working. Doesn't power on and no standby light on the front. I read the forums, and believe it is the power supply board failure. Photos attached, and visual inspection does not reveal an obvious problem (at least to me).
    While plugged in, I test the voltage at the connector (CNM803) that goes to the main board. Voltage on 1-2, 3-4, 5-6, 7-8 is 1.34VDC. 9-10 is of course ground. This test leads me to believe that the PS has failed.

    Also research says that model has a high LED failure rate, so am guessing that is what has caused the PS failure. So after I solve the PS problem, I will have to chase the LED problem. I would like to do a board level repair of the PS if possible, since I'll then have to invest in LED strips.

    Any suggestions on how to solve the PS problem?
    Attached Files

    #2
    Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

    test the diodes .

    Comment


      #3
      Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

      Originally posted by petehall347 View Post
      test the diodes .
      Thanks for the reply! Are you referring to these 4 components that I have highlighted in the attached photo? My multimeter does have a diode setting, but I have never used. Am I just checking to see if they are open?
      Attached Files

      Comment


        #4
        Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

        https://www.badcaps.net/forum/attach...0&d=1598658102

        See that jumper J846 that has label: STB:8V ON:13V, what do you get on that jumper?
        Last edited by budm; 08-28-2020, 08:38 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 UN58J5190AFXZA pwr supply troubleshooting help

          Originally posted by momo2000 View Post
          Set stopped working. Doesn’t power on and no standby light on the front. I read the forums, and believe it is the power supply board failure. Photos attached, and visual inspection does not reveal an obvious problem (at least to me).
          While plugged in, I test the voltage at the connector (CNM803) that goes to the main board. Voltage on 1-2, 3-4, 5-6, 7-8 is 1.34VDC. 9-10 is of course ground. This test leads me to believe that the PS has failed.

          Also research says that model has a high LED failure rate, so am guessing that is what has caused the PS failure. So after I solve the PS problem, I will have to chase the LED problem. I would like to do a board level repair of the PS if possible, since I’ll then have to invest in LED strips.

          Any suggestions on how to solve the PS problem?
          Pin 8 is GND so I cannot see how you get 1.34V, and to have all those pins showing 1.34V it must be measurement error.

          It looks like you count the pins wrong, please look at the chart.
          Odd pins are the exposed pins you can see from the top side of the board, the even pins you have to use skinny probe to probe from wire entrant side of the connector.
          Last edited by budm; 08-28-2020, 08:14 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


            #6
            Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

            Hello,
            It is very common for this board to fail when the leds short. Normally QP801CS on the back of the board is shorted. This is usually the only part that needs to be replaced ( other than the leds) to get it back running. Hope this helps

            Comment


              #7
              Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

              budm: the J846 measures 1.34VDC as well.
              budm: Sorry for the confusion, I just re-measured, pins 1,3,5,7 all measure 1.34VDC.

              Comment


                #8
                Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                Originally posted by nicholas1110 View Post
                Hello,
                It is very common for this board to fail when the leds short. Normally QP801CS on the back of the board is shorted. This is usually the only part that needs to be replaced ( other than the leds) to get it back running. Hope this helps
                Is QP801CS testable with a multimeter?

                Comment


                  #9
                  Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                  What dc Voltage do you have on the main filter cap 120uF 450VDC when measured between the two legs?
                  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


                    #10
                    Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                    Originally posted by budm View Post
                    What dc Voltage do you have on the main filter cap 120uF 450VDC when measured between the two legs?

                    I measured the "main filter cap 120uF 450VDC", circled in red below, and it was 166VDC.
                    Attached Files
                    Last edited by momo2000; 08-29-2020, 01:26 PM.

                    Comment


                      #11
                      Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                      Originally posted by momo2000 View Post
                      I measured the "main filter cap 120uF 450VDC", circled in red below, and it was 166VDC.
                      budm: any thoughts? I reported back the measurement, please let me know what you think. Thanks so much.

                      Comment


                        #12
                        Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                        So the circuit does have Voltage to run the SMPS but the SMPS is not working properly, in standby the the standby Voltage should be 8V and when PS-ON is present the PFC Boost Voltage (around 380 ~ 400VDC on the main filter cap) and the standby output should be 13V.

                        I or someone need to trace out the board to be able to give you test points for you to test next.
                        Last edited by budm; 08-31-2020, 05:03 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


                          #13
                          Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                          Originally posted by budm View Post
                          So the circuit does have Voltage to run the SMPS but the SMPS is not working properly, in standby the the standby Voltage should be 8V and when PS-ON is present the PFC Boost Voltage (around 380 ~ 400VDC on the main filter cap) and the standby output should be 13V.

                          I or someone need to trace out the board to be able to give you test points for you to test next.
                          OK, thank you, I stand at the ready to test and would be most grateful!

                          Comment


                            #14
                            Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                            Have you tested the transistor I mentioned? Remove the board from the tv. On the back of the board is the smd transistor in the location I mentioned before. Put your meter in diode mode, check for short between the center pad and the 2 legs. If your meter reads close to 0.0 it is shorted. If it reads around 0.40 then it is likely good.

                            Comment


                              #15
                              Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                              QP801C (P = PFC) is the MOSFET for the PFC boost Voltage circuit, If it is shorted out then the main fuse will blow, if it not shorted but not working then there will be no boosted Voltage.
                              MOSFET is not tested like BJT.
                              Last edited by budm; 08-31-2020, 10:17 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


                                #16
                                Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                                Originally posted by nicholas1110 View Post
                                Have you tested the transistor I mentioned? Remove the board from the tv. On the back of the board is the smd transistor in the location I mentioned before. Put your meter in diode mode, check for short between the center pad and the 2 legs. If your meter reads close to 0.0 it is shorted. If it reads around 0.40 then it is likely good.
                                nicholas1110: Thanks for the instructions. I cannot find “QP801CS”. I do have a QM801CS. I have attached a photo highlighting this component, is this the correct one? I removed the transistor at that location and tested with my multimeter in diode mode. Here are the results:
                                -Pos lead on left leg, and neg lead on center leg is OL, or no current flow.
                                -Pos lead on right leg, and neg lead on center leg is starts at .45 and increases to .65 over a 30 sec period.
                                For clarity the “legs” are the 3 lead all in a row on the bottom, NOT the pad at top, which I assume is a heat sink.
                                Attached Files

                                Comment


                                  #17
                                  Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                                  Originally posted by budm View Post
                                  QP801C (P = PFC) is the MOSFET for the PFC boost Voltage circuit, If it is shorted out then the main fuse will blow, if it not shorted but not working then there will be no boosted Voltage.
                                  MOSFET is not tested like BJT.
                                  Budm: OK, thanks for the explanation. I “think” I understand.

                                  Comment


                                    #18
                                    Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                                    Originally posted by momo2000 View Post
                                    Budm: OK, thanks for the explanation. I “think” I understand.
                                    QP801C is mounted on the heatsink.
                                    The one you removed is also MOSFET, there are two of them as you can see, they are for driving the power transformer.
                                    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


                                      #19
                                      Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                                      Check out this thread, it should be related to the same part number power supply as yours.
                                      https://www.badcaps.net/forum/showthread.php?t=64699

                                      Comment


                                        #20
                                        Re: Samsung UN58J5190AFXZA pwr supply troubleshooting help

                                        budm and nicholas1110: I have located, desoldered/removed and tested the QP801CS (was screwed to the heatsink).
                                        I have tested with my multimeter in diode mode and below are the results:
                                        Pos on Source (left), Neg on Drain (center) = .544
                                        Pos on Source (left), Neg on Gate (left) = OL

                                        I think this means it is good, right? I was hoping it would be bad, as now I am not sure where to go, any suggestions?

                                        Comment

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