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    Samsung LN 40D630 TV - No Power

    Hi Folks,
    This might be a board replacement project, but wondering if other have had experience with this.
    Picked up a Samsung 40D630 TV, no power. No Standby or other voltages on the PS board. The large caps are not reading any DC, and AC is showing 1.5 V

    I found FM801S (cold side) fuse to be open. I replaced it, but no improvement, and the new Fuse is not blowing up.

    PS board replacement, or is it worth troubleshooting the board (ideally, I'd love to, but I never had one with no voltage on the large caps before)

    Thank you
    Attached Files

    #2
    Re: Samsung LN 40D630 TV - No Power

    Is the fuse on the ac side good? Is your meter working with fresh batteries? Is the ac cord good?

    Comment


      #3
      Re: Samsung LN 40D630 TV - No Power

      Valid questions.. yes, the AC fuse is shorted, and I'm reading good AC on both legs of that fuse. Meter is the one I use, and Yes, I use it to measure the AC.
      Cord is good, and that was my first suspicion.. but another good cord shows the same symptom.

      Incidentally, the Power Supply board is BN44-00464A - Can't seem to find schematic for it.
      Thanks
      Last edited by jason123; 01-10-2019, 11:36 AM.

      Comment


        #4
        Re: Samsung LN 40D630 TV - No Power

        Remove the power supply and check the solder connections on the transformers like TM801S an components connected to the heatsinks.

        Comment


          #5
          Re: Samsung LN 40D630 TV - No Power

          Solder looks ok. They must have some non-conductive coating on the heatsinks. Differential reading on the large caps, shows 162 VDC.. sorry about that.

          Verified again that no voltages are present on the connector to the main board including the 5V standby. So main board is not getting any voltages.

          Diodes on PS boards check out (at least that they're diodes ), no shorted FETs or Diodes that I could find. ESR checks out (low mOhm) on caps around the connector going to Main board.

          Thoughts??
          Last edited by jason123; 01-10-2019, 01:11 PM.

          Comment


            #6
            Re: Samsung LN 40D630 TV - No Power

            SMPS IC UM801S OK?, RM811 OK?
            Fuse FM801S is in the HOT side not cold side, is for supplying the Voltage to run the SMPS IC and the inverter transformer driver circuit.
            Are you 100% sure that FM801S is not blown again? It should have 160VDC with ref to the negative leg of the main filter cap in the cold side.
            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 LN 40D630 TV - No Power

              Verify again Pin 16 on CN802 for A5V. That's your STBY voltage. If there is nothing there, look at the standby circuit of the PSU. Also verify Pin 16 against GND (if there is a short or not).

              Comment


                #8
                Re: Samsung LN 40D630 TV - No Power

                Not sure how to test UM801s, as i can't read the part number. Chip is in good physical shape and no shorts across pins. RM811 reads ~0.5 OHM. FM801S is definitely not open. Pin 16 definitely does not have any voltage. No short on pin 16.

                I stumbled across some shorts that i don't think are right: DP807 AND CP804 are shorted in-circuit. Thanks
                Attached Files
                Last edited by jason123; 01-10-2019, 11:11 PM.

                Comment


                  #9
                  Re: Samsung LN 40D630 TV - No Power

                  Does this IC on your last picture get power?

                  Comment


                    #10
                    Re: Samsung LN 40D630 TV - No Power

                    No, pin 8 referenced to pin 6 (GND) or chassis, does not show any DC voltage (or AC) IC is SEM3040, and according to datasheet, pin 8 is vcc, correct?
                    Last edited by jason123; 01-11-2019, 07:46 AM.

                    Comment


                      #11
                      Re: Samsung LN 40D630 TV - No Power

                      Originally posted by jason123 View Post
                      Not sure how to test UM801s, as i can't read the part number. Chip is in good physical shape and no shorts across pins. RM811 reads ~0.5 OHM. FM801S is definitely not open. Pin 16 definitely does not have any voltage. No short on pin 16.

                      I stumbled across some shorts that i don't think are right: DP807 AND CP804 are shorted in-circuit. Thanks
                      You look at the wrong IC, the one you need to check is UM801S mounted on the heatsink. UP801S is for PFC.

                      Samsung BN44-00464A
                      https://www.shopjimmy.com/samsung-bn...pply-unit.htm#
                      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


                        #12
                        Re: Samsung LN 40D630 TV - No Power

                        Thanks budm.. is there a datsheet for this UM801S? which pin is power I guess . Part number is not legible on the IC
                        Thanks
                        Last edited by jason123; 01-11-2019, 11:10 AM.

                        Comment


                          #13
                          Re: Samsung LN 40D630 TV - No Power

                          please, does anyone has a circuit diagram for this BN44-00464A that they can share?

                          Comment


                            #14
                            Re: Samsung LN 40D630 TV - No Power

                            Originally posted by jason123 View Post
                            Thanks budm.. is there a datsheet for this UM801S? which pin is power I guess . Part number is not legible on the IC
                            Thanks
                            You cannot read anything printing on it at all? there must be something legible on it.
                            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 LN 40D630 TV - No Power

                              Ok, got the better scope, and the part number is STR W6052S
                              Looks like datasheet is:

                              https://cdn.badcaps-static.com/pdfs/...d55e88614f.pdf

                              I am not getting any voltages on any of the pins. No VCC voltage
                              Attached Files

                              Comment


                                #16
                                Re: Samsung LN 40D630 TV - No Power

                                Pin 1 D/ST pin should have about 162VDC (if the IC is not switching) through the primary transformer winding which is fed the fuse that was blown earlier.
                                Last edited by budm; 01-11-2019, 06:04 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


                                  #17
                                  Re: Samsung LN 40D630 TV - No Power

                                  0 dc on pin 1. AC is jumping around 3 to 44 to 2.4 to 0...is it the IC that's bad or transformer replacement you think?
                                  Last edited by jason123; 01-11-2019, 07:08 PM.

                                  Comment


                                    #18
                                    Re: Samsung LN 40D630 TV - No Power

                                    Naturally the new power supply board fixed the problem and the TV is working.. But would love to troubleshoot the Power Supply if at all possible.. if anyone has any ideas, or can share schematic.. I'd be appreciative.
                                    Thank you

                                    Comment


                                      #19
                                      Re: Samsung LN 40D630 TV - No Power

                                      Well, you have good board and bad board for doing the resistance comparison readings.
                                      Check that pin 1 of the SMPS IC again, it should have continuity all the way to that blown fuse.
                                      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


                                        #20
                                        Re: Samsung LN 40D630 TV - No Power

                                        It does.. after taking the measurements yesterday, I guess the fuse did blow again. I also see that pin 1, 3, 5 and 7 of that IC are shorted.
                                        Last edited by jason123; 01-12-2019, 05:07 PM.

                                        Comment

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