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Sony KD-55XF8505 won‘t start

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    Sony KD-55XF8505 won‘t start

    Does anyone have the service manuel for the KD-55XF8505?

    I've already tested a few things and apparently the mainboard is defective and I don't have the exact instructions on how to find out what's defective.

    PSU and T-Con seems to work.

    #2
    Re: Sony KD-55XF8505 won‘t start

    Better 4 you to explain all symptoms, measurements done...

    Comment


      #3
      Re: Sony KD-55XF8505 won‘t start

      Wow, to have mainboard schematics. That would be awesome.
      I assume no responsibility for any stupid suggestions I might post.

      Comment


        #4
        Re: Sony KD-55XF8505 won‘t start

        When I plug in the TV, everything stays black, the status LED also stays off.

        PFC: 390V
        CN6801-2-3-4-5: 75V
        CN6401-5 (STBY3.3V): 3.5V
        CN6401-8 (BL_ERR): 2.3V
        CN6401-13 (REG12V): 12.7V
        CN6401-25 (TCON_VCC12V): 0V

        At the Mainboard (for example at the ICs at the top) there is 3.5V present and also at the wifi board.


        When I try to turn on the TV with the power button or with the remote control, nothing changes.


        Next I checked following:

        CN6401-7 (BL_ON) connected with 3.3V:
        The relay on the PSU clicks and switches

        CN6401-26 (TCON_ON) connected with 3.3V:
        12.7V at T-CON board but no change on panel.

        CN6401-26 (TCON_ON) connected with 3.3V and ribons between mainboard and t-con-board removed:
        12V at T-CON board and the panel changes brigthnes/color. Looks like green <-> black?!
        Attached Files
        Last edited by TobiasG; 09-12-2022, 11:16 PM.

        Comment


          #5
          Re: Sony KD-55XF8505 won‘t start

          check if there is a microcontroller on main board for example called PICxxxxxx, i see it probably neat the green audio jack con., it must to be rewritten, have you got an eprom programmer?

          Comment


            #6
            Re: Sony KD-55XF8505 won‘t start

            No there isnt any called PICxxxxxx :/
            I attached some pictures.
            And yes i own an EPROM programmer
            Attached Files
            Last edited by TobiasG; 09-13-2022, 12:55 AM.

            Comment


              #7
              Re: Sony KD-55XF8505 won‘t start

              what's the marking of IC4001? are there any other spi flash like the 2 you photographed? Is there any IC on the under side of the board?
              Last edited by Davi.p; 09-13-2022, 12:59 AM.

              Comment


                #8
                Re: Sony KD-55XF8505 won‘t start

                Sony often put fuses for protection under the designation Fxxx, there are a lot of them on the board, you need to check them all with a multimeter, and the firmware is in the eMMC (IC2001).
                Attached Files

                Comment


                  #9
                  Re: Sony KD-55XF8505 won‘t start

                  IC4001:

                  Sony CXD4760GG
                  S7NC5S2
                  1826

                  Under the board there isnt anything.

                  And no, I think there only this 2 winbond 25Q16 chips with the flash memory
                  Attached Files

                  Comment


                    #10
                    Re: Sony KD-55XF8505 won‘t start

                    so ic4002 probably stores the stby firmware (i don't comprehend what is PiG) and must be rewritten, try desolder it, freeze it on the programmer and soon read it, then save dump and rewrite it on the same eprom, if it doesn't work another possibilty is there..

                    Comment


                      #11
                      Re: Sony KD-55XF8505 won‘t start

                      I tested the fuses and none seems to be faulty.
                      In the picture I highlighted every tested fuse
                      Attached Files

                      Comment


                        #12
                        Re: Sony KD-55XF8505 won‘t start

                        Originally posted by Davi.p View Post
                        so ic4002 probably stores the stby firmware (i don't comprehend what is PiG) and must be rewritten, try desolder it, freeze it on the programmer and soon read it, then save dump and rewrite it on the same eprom, if it doesn't work another possibilty is there..
                        Stupid question:
                        What is the dumping and re-rewriting with the same dump supposed to do? If the chip is defective or no longer holds the correct data, then nothing changes with a new flashing of it, right?

                        And PiQ maybe stands for:
                        Prefetch Input Queue
                        Last edited by TobiasG; 09-13-2022, 03:56 AM.

                        Comment


                          #13
                          Re: Sony KD-55XF8505 won‘t start

                          Originally posted by lotas View Post
                          Sony often put fuses for protection under the designation Fxxx, there are a lot of them on the board, you need to check them all with a multimeter, and the firmware is in the eMMC (IC2001).

                          Yes IC2001 is the eMMC (Samsung KLMAG1JETD-B041).
                          But could it be, that the firmware is faulty?
                          And if so, how could I test or fix this?
                          Last edited by TobiasG; 09-13-2022, 03:57 AM.

                          Comment


                            #14
                            Re: Sony KD-55XF8505 won‘t start

                            It is not the same reading normally the eprom and reading after freezing

                            Comment


                              #15
                              Re: Sony KD-55XF8505 won‘t start

                              Originally posted by TobiasG View Post
                              Yes IC2001 is the eMMC (Samsung KLMAG1JETD-B041).
                              But could it be, that the firmware is faulty?
                              And if so, how could I test or fix this?
                              Yes, there may be a problem in it, the bootloader is located in it, only the EMMC programmer and a known working dump for this chassis will help here.

                              Comment


                                #16
                                Re: Sony KD-55XF8505 won‘t start

                                Briefly summarized:
                                So we all assume that the motherboard is defective and nothing else, right?
                                I have already ordered a used, tested mainboard (which I could send back, if i could find the problem with mine).

                                If it's the eMMC, then I can't get any further without a dump and programmer anyway, and unfortunately I couldn't find anything here in the forum or on google.

                                And I could still do that with the eeproms, but I'm wondering if it's worth the effort, since I almost don't assume that it's their fault?!
                                Theoretically, if the other board is delivered, I could also dump the eeproms from this board (using a clip) and then flash them again at my old board.
                                Last edited by TobiasG; 09-13-2022, 04:25 AM.

                                Comment


                                  #17
                                  Re: Sony KD-55XF8505 won‘t start

                                  Most likely they (SPI Flash) refer to T-Con, (settings for different matrices).
                                  Attached Files

                                  Comment


                                    #18
                                    Re: Sony KD-55XF8505 won‘t start

                                    Originally posted by lotas View Post
                                    Most likely they (SPI Flash) refer to T-Con, (settings for different matrices).
                                    I also assume that the fault is not there, since the TV shows no reaction at all. Or did I misunderstand you?

                                    For me as a layman it really sounds more like the bootloader. And is that also correct, if something doesn't fit there, the CN6401-8 (BL_ERR) just doesn't deliver 0V but like at my point 2.3V

                                    Comment


                                      #19
                                      Re: Sony KD-55XF8505 won‘t start

                                      Try to make a hard reset by pressing the buttons and connecting to the power supply.
                                      Attached Files
                                      Last edited by lotas; 09-13-2022, 05:01 AM.

                                      Comment


                                        #20
                                        Re: Sony KD-55XF8505 won‘t start

                                        Originally posted by lotas View Post
                                        Try to make a hard reset by pressing the buttons and connecting to the power supply.
                                        Unfortunately, I've tried that before, but without success

                                        Comment

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