Samsung UN40EH5300F No Power

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  • meantomatoes
    Member
    • Jun 2018
    • 28
    • United States

    #1

    Samsung UN40EH5300F No Power

    it's the power board, i know that, but i'd rather not replace it. no backlight, no standby. none of the capacitors look bulgy, fuse is good i think. can yall help me figure out what's wrong? i barely know how to use a multimeter or how to troubleshoot a circuit board but i measured ac voltage and it's like 120-140 volts up until the bridge rectifier and it turns to about 340. voltage remains that up until the legs of the transformer that meets the hot and cold side where it goes to 0 on the output of the transformer. is that normal? sometimes if i plug it in with just CNL802 (backlight) and not CNM803 (main board) the backlight flickers on but then goes off and stays off and won't do it again. it was making a baby lightning bolt when i measured DC voltage on some of the components by CNL802 but now it doesn't do it anymore. pictures are from shopjimmy, board is BN44-00666A
    Attached Files
  • CapLeaker
    Leaking Member
    • Dec 2014
    • 8148
    • Canada

    #2
    Re: Samsung UN40EH5300F No Power

    check the connector that goes to the PSU for burnt contacts.
    With the PSU turned off, there should be 170V DC on the main filter cap. You can unplug the main board from the PSU, plug the back lights in, then plug the PSU into mains circuit. The PSU should come on and the back lights should be on and stay on. The flickering could have been an back light led going bad. Pin 12 is A5V, so this pin should have 5V STBY all the time.
    Last edited by CapLeaker; 06-05-2018, 07:05 PM.

    Comment

    • meantomatoes
      Member
      • Jun 2018
      • 28
      • United States

      #3
      Re: Samsung UN40EH5300F No Power

      Originally posted by CapLeaker
      check the connector that goes to the PSU for burnt contacts.
      With the PSU turned off, there should be 170V DC on the main filter cap. You can unplug the main board from the PSU, plug the back lights in, then plug the PSU into mains circuit. The PSU should come on and the back lights should be on and stay on. The flickering could have been an back light led going bad. Pin 12 is A5V, so this pin should have 5V STBY all the time.
      not measuring any DC voltage at either leg of the main filter cap. that's the blue one correct? i put a probe on the leg and the other on the ground right? i don't know anything about this stuff.

      so while the board is plugged in, disconnect the main board with the backlight not plugged in, then plug in the backlight and then the main board? this did nothing.

      measured DC voltage of CNL802 and CNM803 using the method in 1st pg. i have a cheap multimeter so this might be why the readings fluctuate? can't afford a nice one, that's why i'm avoiding replacing the whole board.
      • CNM803 is dead on all pins, 0 volts.
      • on CNL802, pins 1-2 make a blue spark, jump to ~375 and slowly fall to ~295, repeating the cycle every 2-4 seconds.
      • pins 3-4 do the same but jump to ~340 falling to ~260 with spark.
      • pin 5 is dead.
      • pins 6-7 jump to ~310 falling to ~240, no spark.
      • pins 8-9 jump to ~280 and fall to ~220, no spark.


      hope this helps

      Comment

      • budm
        Badcaps Legend
        • Feb 2010
        • 40746
        • USA

        #4
        Re: Samsung UN40EH5300F No Power

        Put the DC Volt two meter's probes at each leg of the main filter cap CM804S, report then reading.
        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

        • meantomatoes
          Member
          • Jun 2018
          • 28
          • United States

          #5
          Re: Samsung UN40EH5300F No Power

          Originally posted by budm
          Put the DC Volt two meter's probes at each leg of the main filter cap CM804S, report then reading.
          yup, 170 volts not fluctuating

          Comment

          • nomoresonys
            Badcaps Legend
            • Jan 2013
            • 12184
            • U.S.

            #6
            Re: Samsung UN40EH5300F No Power

            Originally posted by meantomatoes
            yup, 170 volts not fluctuating
            There's 2 parts to this test, the 170 seems about right, now hit the power button see if it goes up to about 380 or so, if so that part is ok, BE CAREFUL, this is the HOT/DEADLY side of the powersupply.
            Last edited by nomoresonys; 06-06-2018, 07:12 AM.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #7
              Re: Samsung UN40EH5300F No Power

              There is NO PFC Voltage booster so the Voltage on the cap will remain around 160V or so, the power supply is an always on power supply since it is the only power supply on that board, some of the outputs are switched (the one with 'B' marking).
              I would like to see the pictures of YOUR board since there may be something that you did not see on your board.
              DM851C is the rectifier diode for the A5V.
              I would check all 7 diodes on the cold side.
              Last edited by budm; 06-06-2018, 10:14 AM.
              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

              • CapLeaker
                Leaking Member
                • Dec 2014
                • 8148
                • Canada

                #8
                Re: Samsung UN40EH5300F No Power

                I would start investigating why A5V isn't there. On the back side the A5V goes through 2 jumpers and goes to a surface mount diode. check it out.

                Comment

                • R_J
                  Badcaps Legend
                  • Jun 2012
                  • 9535
                  • Canada

                  #9
                  Re: Samsung UN40EH5300F No Power

                  Can you provide the number on the ic on the HOT side (ic???1S) Is it a (SSC2S110) by chance? I suspect it should be operating in standby mode, which would produce the needed 5 volt standby, when the power on signal comes, opto (pc???1s) puts the ic into full on operation. and you should get the other voltages
                  Last edited by R_J; 06-06-2018, 11:51 AM.

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Samsung UN40EH5300F No Power

                    Originally posted by budm
                    There is NO PFC Voltage booster so the Voltage on the cap will remain around 160V or so, the power supply is an always on power supply since it is the only power supply on that board, some of the outputs are switched (the one with 'B' marking).
                    I would like to see the pictures of YOUR board since there may be something that you did not see on your board.
                    DM851C is the rectifier diode for the A5V.
                    I would check all 7 diodes on the cold side.
                    The two SMD MOSFETs on the bottom side of the board; One is for B5V and another one is for B13V; they are turned on when PS-ON is present.
                    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

                    • meantomatoes
                      Member
                      • Jun 2018
                      • 28
                      • United States

                      #11
                      Re: Samsung UN40EH5300F No Power

                      Originally posted by budm
                      There is NO PFC Voltage booster so the Voltage on the cap will remain around 160V or so, the power supply is an always on power supply since it is the only power supply on that board, some of the outputs are switched (the one with 'B' marking).
                      I would like to see the pictures of YOUR board since there may be something that you did not see on your board.
                      DM851C is the rectifier diode for the A5V.
                      I would check all 7 diodes on the cold side.
                      DM851C has no resistance in either direction, DM852C and DM853C have something wonky where they slowly increase slower and slower in the correct orientation to like 8k ohms (is that right? the dial is on 20k and it's showing ~8.00) and then slowly decrease with the opposite direction. DM855C-DM858C have ~16k ohms and then ~100k the opposite way.

                      Originally posted by R_J
                      Can you provide the number on the ic on the HOT side (ic???1S) Is it a (SSC2S110) by chance? I suspect it should be operating in standby mode, which would produce the needed 5 volt standby, when the power on signal comes, opto (pc???1s) puts the ic into full on operation. and you should get the other voltages
                      IC? where would that be?
                      Attached Files

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: Samsung UN40EH5300F No Power

                        OK the Diodes are not shorted.
                        Check DM851C in diode mode to see what you get.
                        The SMPS IC in question is ICM801S, it is the SMD 7-PIN IC.
                        BTW, when you tested the DC V on the cold side connector, is the board connected to the main board? If it is then try running the power supply board by itself to see what dc V you will get on the cold side connector.
                        Last edited by budm; 06-06-2018, 01:59 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

                        • meantomatoes
                          Member
                          • Jun 2018
                          • 28
                          • United States

                          #13
                          Re: Samsung UN40EH5300F No Power

                          Originally posted by budm
                          OK the Diodes are not shorted.
                          Check DM851C in diode mode to see what you get.
                          The SMPS IC in question is ICM801S, it is the SMD 7-PIN IC.
                          BTW, when you tested the DC V on the cold side connector, is the board connected to the main board? If it is then try running the power supply board by itself to see what dc V you will get on the cold side connector.
                          DM851C shows 001, DM852C and DM853C show 328, and DM855C-DM858C show ~448.

                          for the IC, i assume you mean the number printed on it and not the voltage or anything? it's 3S111, SK391, 267(and maybe a 1 or I or L)

                          Comment

                          • budm
                            Badcaps Legend
                            • Feb 2010
                            • 40746
                            • USA

                            #14
                            Re: Samsung UN40EH5300F No Power

                            Hmm, I would remove DM851C and re-test again in Diode mode.
                            I found the picture of the IC but not the spec. sheet.
                            https://www.aliexpress.com/item/LCD-...469463424.html
                            Last edited by budm; 06-06-2018, 03:55 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

                            • meantomatoes
                              Member
                              • Jun 2018
                              • 28
                              • United States

                              #15
                              Re: Samsung UN40EH5300F No Power

                              Originally posted by budm
                              Hmm, I would remove DM851C and re-test again in Diode mode.
                              I found the picture of the IC but not the spec. sheet.
                              https://www.aliexpress.com/item/LCD-...469463424.html
                              same reading

                              Comment

                              • R_J
                                Badcaps Legend
                                • Jun 2012
                                • 9535
                                • Canada

                                #16
                                Re: Samsung UN40EH5300F No Power

                                The ic is similar to this SSC1S311, pin 1 is controlled by the opto to switch the ic out of standby condition. Check the voltage on pin 4 using the main cap's negative for meter ground
                                Sometimes one of those series resistors coming from the main cap's (+) goes open.
                                Attached Files

                                Comment

                                • neilc6
                                  Badcaps Legend
                                  • Nov 2015
                                  • 1550
                                  • Canada

                                  #17
                                  Re: Samsung UN40EH5300F No Power

                                  That board is $25 on ebay shipped. Not sure why you don't just buy another one. I had scrapped some 50" Samsung LED TVs and found out after that the boards were selling for $10 to $20 on ebay with shipping.
                                  Last edited by neilc6; 06-06-2018, 05:30 PM.

                                  Comment

                                  • meantomatoes
                                    Member
                                    • Jun 2018
                                    • 28
                                    • United States

                                    #18
                                    Re: Samsung UN40EH5300F No Power

                                    Originally posted by R_J
                                    The ic is similar to this SSC1S311, pin 1 is controlled by the opto to switch the ic out of standby condition. Check the voltage on pin 4 using the main cap's negative for meter ground
                                    Sometimes one of those series resistors coming from the main cap's (+) goes open.
                                    should i put the diode back on before testing?


                                    Originally posted by neilc6
                                    That board is $25 on ebay shipped. Not sure why you don't just buy another one. I had scrapped some 50" Samsung LED TVs and found out after that the boards were selling for $10 to $20 on ebay with shipping.
                                    seems wasteful to me

                                    Comment

                                    • R_J
                                      Badcaps Legend
                                      • Jun 2012
                                      • 9535
                                      • Canada

                                      #19
                                      Re: Samsung UN40EH5300F No Power

                                      Originally posted by meantomatoes
                                      should i put the diode back on before testing?
                                      ??? what diode??
                                      There are a series of 3 resistors that go from the main cap positive to supply the ic with its vcc voltage, If its not there the ic won't operate.
                                      Last edited by R_J; 06-06-2018, 06:03 PM.

                                      Comment

                                      • budm
                                        Badcaps Legend
                                        • Feb 2010
                                        • 40746
                                        • USA

                                        #20
                                        Re: Samsung UN40EH5300F No Power

                                        Originally posted by meantomatoes
                                        same reading
                                        001 in both directions?
                                        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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