Samsung UE55MU6120K Boot loop with backlight no video

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  • fanaticgames
    Senior Member
    • May 2017
    • 138
    • italy

    #61
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by Davi.p
    Now that we have listen to the others would you like to follow my advice? what do you think?
    to inject a voltage from 12 to 15 I need a bench power supply that I don't have, I thought I'd solve it in another way

    Comment

    • Davi.p
      Hobbist
      • Sep 2009
      • 4264
      • Italy - Milan

      #62
      Re: Samsung UE55MU6120K Boot loop with backlight no video

      no read my post about the jumper wire..

      Comment

      • fanaticgames
        Senior Member
        • May 2017
        • 138
        • italy

        #63
        Re: Samsung UE55MU6120K Boot loop with backlight no video

        Originally posted by Davi.p
        no read my post about the jumper wire..
        I've already bridged those points

        Comment

        • fanaticgames
          Senior Member
          • May 2017
          • 138
          • italy

          #64
          Re: Samsung UE55MU6120K Boot loop with backlight no video

          Originally posted by fanaticgames
          I've already bridged those points
          kept on even more than 3 minutes nothing heats up on the display board, in fact I tried 5 times, 4 times the TV restarts the same repeatedly, only once it stayed on, the only thing I noticed was a hum in this area but nothing else
          Attached Files

          Comment

          • Davi.p
            Hobbist
            • Sep 2009
            • 4264
            • Italy - Milan

            #65
            Re: Samsung UE55MU6120K Boot loop with backlight no video

            so to be more clear, TRDY jumpered , but not the ones told to you by Diah, the ones actually marked as them, no tape on the flats, and it keeps restarting? i don' think so, i remember you posted only one picture clear of TRDY point, and the other one?

            Comment

            • fanaticgames
              Senior Member
              • May 2017
              • 138
              • italy

              #66
              Re: Samsung UE55MU6120K Boot loop with backlight no video

              Originally posted by Davi.p
              so to be more clear, TRDY jumpered , but not the ones told to you by Diah, the ones actually marked as them, no tape on the flats, and it keeps restarting? i don' think so, i remember you posted only one picture clear of TRDY point, and the other one?
              read above, united points (the correct ones I assume because without flats they don't restart), with all flats the result is that only once it doesn't turn off, it keeps restarting with the variant that emits a bad buzz in that area of the motherboard , all components are cold except for the cpu which is slightly warm

              Comment

              • Davi.p
                Hobbist
                • Sep 2009
                • 4264
                • Italy - Milan

                #67
                Re: Samsung UE55MU6120K Boot loop with backlight no video

                Ok, so without a bench PSU i can only suggest this type of test, remove each one of the diode packs on the screen's boards, test entire tv after each removing, if it doesn't change (i think is not there the problem), repeat same thing also with the bigger caps that are probably on the Avdd/15v line..
                just to be clear, the buzzing noise confirms that there is a short circuit on the screen
                Last edited by Davi.p; 02-22-2023, 02:48 AM.

                Comment

                • fanaticgames
                  Senior Member
                  • May 2017
                  • 138
                  • italy

                  #68
                  Re: Samsung UE55MU6120K Boot loop with backlight no video

                  Originally posted by Davi.p
                  Ok, so without a bench PSU i can only suggest this type of test, remove each one of the diode packs on the screen's boards, test entire tv after each removing, if it doesn't change (i think is not there the problem), repeat same thing also with the bigger caps that are probably on the Avdd/15v line..
                  just to be clear, the buzzing noise confirms that there is a short circuit on the screen
                  for information when I did the tests with scotch tape I also isolated the vcom and avdd signal and it always restarts

                  Comment

                  • Davi.p
                    Hobbist
                    • Sep 2009
                    • 4264
                    • Italy - Milan

                    #69
                    Re: Samsung UE55MU6120K Boot loop with backlight no video

                    and which is the question? the masking suggestion is not by me, you must ask to the owners, avdd and vcom must not be isolated
                    Last edited by Davi.p; 02-22-2023, 03:30 AM.

                    Comment

                    • PaolinaSparks
                      New Member
                      • Feb 2023
                      • 4
                      • Germany

                      #70
                      Re: Samsung UE55MU6120K Boot loop with backlight no video

                      Originally posted by fanaticgames
                      nothing changes, it always restarts, i guess the ckv lines have nothing to do with it at this point
                      please excuse my stupid question
                      But to really rule everything out please tell me which photo is which cable and if it is mainboard side or gate driver side.

                      Comment

                      • fanaticgames
                        Senior Member
                        • May 2017
                        • 138
                        • italy

                        #71
                        Re: Samsung UE55MU6120K Boot loop with backlight no video

                        Originally posted by PaolinaSparks
                        please excuse my stupid question
                        But to really rule everything out please tell me which photo is which cable and if it is mainboard side or gate driver side.
                        the tape was put on correctly
                        Attached Files

                        Comment

                        • fanaticgames
                          Senior Member
                          • May 2017
                          • 138
                          • italy

                          #72
                          Re: Samsung UE55MU6120K Boot loop with backlight no video

                          Originally posted by Davi.p
                          and which is the question? the masking suggestion is not by me, you must ask to the owners, avdd and vcom must not be isolated
                          the question is isolating those 2 lines (avdd and vcom) shouldn't it turn on and not restart if the short is there? do you think the short could be on avdd? so your suggestion is to inject the 15v directly on one of the two display boards with everything connected?

                          Comment

                          • Davi.p
                            Hobbist
                            • Sep 2009
                            • 4264
                            • Italy - Milan

                            #73
                            Re: Samsung UE55MU6120K Boot loop with backlight no video

                            if masked avdd or vcom the mainboard circuitry goes in trouble and reboots, injecting on avdd can pop a suspected bad cap so you can replace it, but 12v are enough, the important is that 1,8v/3,3v must be present, therefore cof are powered.. prepare to switch off everything when you see smoke, but pay attention first on screen's glued ribbons, them must not burn!

                            Comment

                            • fanaticgames
                              Senior Member
                              • May 2017
                              • 138
                              • italy

                              #74
                              Re: Samsung UE55MU6120K Boot loop with backlight no video

                              Originally posted by Davi.p
                              if masked avdd or vcom the mainboard circuitry goes in trouble and reboots, injecting on avdd can pop a suspected bad cap so you can replace it, but 12v are enough, the important is that 1,8v/3,3v must be present, therefore cof are powered.. prepare to switch off everything when you see smoke, but pay attention first on screen's glued ribbons, them must not burn!
                              the 3,3 are present only for a moment as the tv restarts every 2/3 seconds

                              Comment

                              • Davi.p
                                Hobbist
                                • Sep 2009
                                • 4264
                                • Italy - Milan

                                #75
                                Re: Samsung UE55MU6120K Boot loop with backlight no video

                                is there any 1,8v? you must check which of these two voltages are present on the smaller caps near the source cofs therefore the ribbons on the bottom side, that tension must be provided constantly to the panel toghether with avdd

                                Comment

                                • PaolinaSparks
                                  New Member
                                  • Feb 2023
                                  • 4
                                  • Germany

                                  #76
                                  Re: Samsung UE55MU6120K Boot loop with backlight no video

                                  Originally posted by fanaticgames
                                  the tape was put on correctly
                                  I hope you forgive me. How could I doubt you

                                  Comment

                                  • PaolinaSparks
                                    New Member
                                    • Feb 2023
                                    • 4
                                    • Germany

                                    #77
                                    Re: Samsung UE55MU6120K Boot loop with backlight no video

                                    Originally posted by fanaticgames
                                    Nope, I didn't find any shorted capacitors
                                    Have you tested the resistors and diodes too?

                                    And I can still recommend disconnecting the Bluetooth module. A defect in it can also cause the error.

                                    Comment

                                    • fanaticgames
                                      Senior Member
                                      • May 2017
                                      • 138
                                      • italy

                                      #78
                                      Re: Samsung UE55MU6120K Boot loop with backlight no video

                                      Originally posted by Davi.p
                                      is there any 1,8v? you must check which of these two voltages are present on the smaller caps near the source cofs therefore the ribbons on the bottom side, that tension must be provided constantly to the panel toghether with avdd
                                      I check as soon as possible, I test as soon as I can with a bench power supply and you update

                                      Comment

                                      • fanaticgames
                                        Senior Member
                                        • May 2017
                                        • 138
                                        • italy

                                        #79
                                        Re: Samsung UE55MU6120K Boot loop with backlight no video

                                        I have an update, as usual strange things only happen to me, I left the TV off for 3/4 days with the bridge on points RDY1 and RDY3 today I borrow a friend's thermal imaging camera and turn on the TV (with the bridge and the connected flats) and immediately after 1 second I see these 2 components (in the photo) heating up so much, I disconnect the bridge and turn the TV back on and it works, the whole display works, you see
                                        Attached Files

                                        Comment

                                        • lotas
                                          Badcaps Legend
                                          • Jan 2016
                                          • 4458
                                          • Russia

                                          #80
                                          Re: Samsung UE55MU6120K Boot loop with backlight no video

                                          You didn't seem to put a jumper there.
                                          Attached Files

                                          Comment

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