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BN44-00265A schematic needed

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    BN44-00265A schematic needed

    Hi,

    I'm working on a Samsung LN46B550K1FXZA where the backlights attempt to turn on. Cycles four or five times with the backlights briefly coming on - then stops trying.
    I found 2 bad FDPF12N50UT mosfets so far and would like to identify some of the surface mount parts in that area.
    I found schematics for boards with similar numbers but the BN44-00265A is different.
    Thanks.

    Mike

    #2
    Re: BN44-00265A schematic needed

    elektrotanya.com/ has it. I found it but Sat. internet is too slow for me to doownload and post it

    Comment


      #3
      Re: BN44-00265A schematic needed

      I did download the service manual for the set but unless I missed something, the schematic for the power supply wasn't there.
      I can't find a listing for just the power supply.

      Mike

      Comment


        #4
        Re: BN44-00265A schematic needed

        Well I tried

        Comment


          #5
          Re: BN44-00265A schematic needed

          What is the board not doing?
          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: BN44-00265A schematic needed

            Originally posted by mu2 View Post
            Hi,

            I'm working on a Samsung LN46B550K1FXZA where the backlights attempt to turn on. Cycles four or five times with the backlights briefly coming on - then stops trying.
            I found 2 bad FDPF12N50UT mosfets so far and would like to identify some of the surface mount parts in that area.
            I found schematics for boards with similar numbers but the BN44-00265A is different.
            Thanks.

            Mike
            not precisely what you asked for but the B version. looks fairly similar, different transformers and looks like the FDPF12N50 have been increased to 16A versions FDPF16N50

            SJ shows 265A,265B,& 266A boards interchangeable,

            Even if it's not 100%, if you look up datasheets for the same components in the B version and find out the case marking, maybe then compare that data back to what you see on your board?
            Attached Files

            Comment


              #7
              Re: BN44-00265A schematic needed

              It is strange that the backlights will flash 4~5 times in sync with cycling on and off without going into inverter shutdown mode and stays in shutdown mode after fail in first attempt. I wonder if the BL_ON is going up and down or the PS_ON is cycling.
              Were those two MOSFETs failed as shorted?
              C1804 (0.68uF 500V) in rev B board is also known for loosing its capacitance.
              BTW, the PS_ON and the Inverter ON/OFF pins have pull-up resistors, so if you disconnect the cable between the power supply/inverter board board, the backlights should come on the minute you plug the TV into the AC outlet.
              Last edited by budm; 08-21-2014, 08:26 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


                #8
                Re: BN44-00265A schematic needed

                Budm,

                The mosfets did not fail shorted. They have no gain when testing with my Cricket. The heatsinks were discolored from high temperature around the mosfets. When I removed the parts there was very little thermal paste to transfer the heat.
                I had two FQPF13N50C that I thought would be a good sub but my symptom is similar now. I haven't researched the difference between the FQPF and FDPF lines.
                I still need to pull the replacement parts out again and see if they also failed.
                I haven't spent a lot of time on this set and I'll use your suggestions to scope some signals and check the cap. I did get the BN44-00265B and saw the mosfet upgrade. I think that my version uses different driver circuitry before the mosfets. I didn't have much luck crossing the surface mount component markings to something that made sense- that's why I wanted the schematic.
                Thanks again for all your responses.

                Mike

                Comment


                  #9
                  Re: BN44-00265A schematic needed

                  Budm,

                  I did a little more testing.
                  The .68 uf cap is at location C1825 on this version of the power supply - it tests good.
                  I was off on the number of cycles - the set cycles 3 times then shuts down.
                  Disconnecting the cable between the power supply and inverter makes no difference - I have the same 3 cycle problem with the backlights flashing on briefly and then shut down.
                  The inverter on/off pin is also cycling from 0 - 5 volts. The 5 volt and 12 volt supplies appear ok.
                  So, is the main board bad?
                  Could the eeprom be corrupt? Can I stick a blank eeprom in it's place and then hopefully go into the service menu and set parameters?

                  Mike

                  Comment


                    #10
                    Re: BN44-00265A schematic needed

                    Hi,

                    Still no luck on this Samsung. I pulled the replacement mosfets out and they are ok.
                    I did find a thread on the internet describing practically the same problem.

                    http://www.justanswer.com/tv-repair/...ing-black.html

                    The tech and the set's owner finally gave up.

                    Anyone ever fix this symptom? Bad bulb?
                    Anyone know the location and part number of the eeprom?

                    Thanks,
                    Mike

                    Comment


                      #11
                      Re: BN44-00265A schematic needed

                      "The inverter on/off pin is also cycling from 0 - 5 volts." This signal is generated by the main board, so something on the main board is not right. You can use external 3VDC pwoer source to force on the inverter, use 2 AA and a 100~500 Ohms resistor in series with the + of the batteries to feed into the BL_ON PIN, but you must remove the bl_on wire from the inverter board so the main board will not force it in the LOW condition.
                      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: BN44-00265A schematic needed

                        any updates on this tv? I got the same issue I have tried replacing everything and can not get it.

                        Comment


                          #13
                          Re: BN44-00265A schematic needed

                          I gave up on the set and sent it back to the recycling center.
                          Sorry.

                          Mike

                          Comment


                            #14
                            Re: BN44-00265A schematic needed

                            Yeah I don't understand what it is I changed everything. Is it possible panel is bad. Even when power supply and inverter alone is connected it does it. Yesterday I changed inverter as last thing and it stayed on for like 30 mind then I turned it off. Today I went down to turn it on and it did it again.

                            Comment


                              #15
                              Re: BN44-00265A schematic needed

                              Figured it out thanks to you tube. After I had the set for over a month and changed everyboard. You have to cut the jumper jp854 I tried it on the new and old power supply works great

                              Comment


                                #16
                                Re: BN44-00265A schematic needed

                                Originally posted by mattstolte View Post
                                Figured it out thanks to you tube. After I had the set for over a month and changed everyboard. You have to cut the jumper jp854 I tried it on the new and old power supply works great
                                Rarely a permanent fix on these -- it just hides a problem which will come back (low PFC voltage tripping UVP circuit)
                                Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                                For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                                Comment


                                  #17
                                  Re: BN44-00265A schematic needed

                                  Where is the low voltage coming from then?

                                  Comment

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