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    Samsung LA32R81B Not Turning On

    Hi guys,

    Well, my first post here was resolved with you guys helping me trying to resolve my LG No screen issue, bad tcon board and when it was replaced, it was working until today. My issue now is with another TV, a Samsung brand. The history of it was that suddenly it did not turn on so I opened it up and saw 3 bloated caps CM856,CM860, CB852 so replaced those 3 and tried to turn it on, but nothing, the when plug in, the red light will light up and then will turn on, but no display and no backlight being seen. Tried to do a voltage reading;

    Main cap, will fluctuate even when on standby will read voltage 383 then drop to 350 then goes up again. Turning it on will have the same scenario.
    PS - 0
    SB - 5V
    A5 - 3.1
    B5 - 3.1
    No 12V, 13V or 24V on those connectors.
    Checked all the diodes and all are good. Checked the zener diode DZM854 and it is okay, checked some capacitors that can be tested using my digital meter, (up to 200MFD only) and all is well. Not sure anymore where to check. Any help will be appreciated. Thanks guys.
    Attached Files

    #2
    Re: Samsung LA32R81B Not Turning On

    Looks like the mainboard is not turning on PS. Disconect the main board from the power supply and connect a 1K resistor between SB and PS then check the voltages.
    There's a lot of oxided component legs and jumper links that could be cleaned up.
    Last edited by dick_barton; 07-08-2020, 09:20 AM.
    Willing to help but I'm no expert.

    Comment


      #3
      Re: Samsung LA32R81B Not Turning On

      Thanks for the advise dick, what is the wattage that I should use to do this? or it does not matter as long as it is a 1k resistor? Don't have any available right now and will purchase tomorrow to do this advise.

      Comment


        #4
        Re: Samsung LA32R81B Not Turning On

        Also check your solder work, look real closely make sure they are good.

        Comment


          #5
          Re: Samsung LA32R81B Not Turning On

          Thanks guys, will try to resolder and clean those oxidized terminals tomorrow and then do the 1k resistor. Will update about the result.

          Comment


            #6
            Re: Samsung LA32R81B Not Turning On

            1) We need to see the straight shots pictures of the whole top and bottom side of the board (BN44-00192A).
            2) The board had bad brown glues that need to be removed, it is conductive and corrosive.
            3) From post #1:Are you sure you count the pins correctly? We also need the Voltage readings of all the pins.
            PS - 0
            SB - 5V
            A5 - 3.1
            B5 - 3.1
            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 LA32R81B Not Turning On

              Tried to cleaned and remove those brown glue as much as I can, bench test the power board and here are the result.

              SB - 5.17
              PS - 4.14
              12V - 0
              13V - 0.49
              5.3V - 0
              24V - 0
              Main cap - 379

              I have those voltage check on the same pin where I put the 1k resistor.

              Thanks a lot.
              Attached Files

              Comment


                #8
                Re: Samsung LA32R81B Not Turning On

                Check RM801 (0.22 Ohms MOX).
                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 LA32R81B Not Turning On

                  Desoldered this resistor and checked using digital meter, x200 and the reading is 00.6, if i short the test leads it will have 00.4 so I think the range is in 00.2. Thanks budm.

                  Comment


                    #10
                    Re: Samsung LA32R81B Not Turning On

                    Can you measure the voltages very very carefully on ICM801 (MC33067)

                    Pin 15 = Vcc =
                    Pin 11 = Soft Start =
                    Pin10 = Fault Input =
                    Pin 5 = Vref

                    Use the negative leg of CP803 as the (hot) ground connection
                    Attached Files
                    Last edited by dick_barton; 07-09-2020, 05:28 AM.
                    Willing to help but I'm no expert.

                    Comment


                      #11
                      Re: Samsung LA32R81B Not Turning On

                      Hi Dick,

                      Here are the test,

                      Pin 15 = 15.04 x 20VDC
                      Pin 11 = 0.18 x 20VDC
                      Pin 10 = 0
                      Pin 5 = 5.02

                      Comment


                        #12
                        Re: Samsung LA32R81B Not Turning On

                        So the ICM801 has a good operating supply voltage and Vref @ 5V is correct.

                        However Csoft_start I think should have 2.5V at its pin which is shorted out by QM805 if the voltage across RM824 is less than 2.5V

                        Can you check the voltage across RM824. If it's less than 2.5V then you will need to lift the resistors connected in series with it that go to the PFC supply and check each one.

                        Trying to test them in circuit does not always give true results.
                        Willing to help but I'm no expert.

                        Comment


                          #13
                          Re: Samsung LA32R81B Not Turning On

                          Well, was going to try a voltage check, but when I plug in the board, heard a slight pop, so unplug it immediately and check, now the RB809 is open, from the schematic you have provided it should be 2ohms, but I have no reading.

                          Comment


                            #14
                            Re: Samsung LA32R81B Not Turning On

                            Maybe check all the little ceramic caps on the bottom of the board surrounding ICM801, maybe check them for shorts and very low ohms.
                            Last edited by nomoresonys; 07-10-2020, 09:20 AM.

                            Comment


                              #15
                              Re: Samsung LA32R81B Not Turning On

                              Not looking so good at the moment.

                              With the set disconnected from the wall power socket can you measure the resistance between pins 7 (or 8 ) to pin 1 of ICB801S to check if the internal mosfet is short circuited.

                              If it is you will need to replace it along with the resistor.

                              In the meantime you could measure the resistors I mentioned earlier, RM819 to RM824
                              Willing to help but I'm no expert.

                              Comment


                                #16
                                Re: Samsung LA32R81B Not Turning On

                                will do, anyways the 6.3 fuse blown, can I replace it will a glass fuse 5A, the electronic shop does not have the 6.3 fuse i showed them.

                                Comment


                                  #17
                                  Re: Samsung LA32R81B Not Turning On

                                  You need to find out what caused the fuse to blow before thinking of replacing it.
                                  Willing to help but I'm no expert.

                                  Comment


                                    #18
                                    Re: Samsung LA32R81B Not Turning On

                                    hi, checked for any shorted components, when I put my test leads in the main cap, there is a short in the circuit, so trace the lines, remove the main cap, still shorted, follow all the lines of the main cap and there's a short in the icb801s. pin 1 is shorted to pin 8, so desoldered the said ic and indead they are short, replaced it with same ic but still havent tested the board since I still have no fuse, will it be okay if I used a 5a glass fuse? Electronic shop have no fuse for 6.3a. thanks guys

                                    Comment


                                      #19
                                      Re: Samsung LA32R81B Not Turning On

                                      also check those resistors you have mentioned and they are within specs

                                      Comment


                                        #20
                                        Re: Samsung LA32R81B Not Turning On

                                        I never like glass fuses because if there is a short circuit they can explode and the glass fly everywhere.
                                        Always best to use a ceramic fuse which matches the rated current and note if it's quick blow or time delay
                                        Willing to help but I'm no expert.

                                        Comment

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