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Sony KDL-55W755C - Dead

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    #1

    Sony KDL-55W755C - Dead

    Hello again lifesavers.

    I have a KDL-55W755c that came in dead - not even standby light going on. Tested the power supply - all correct. Tested the output pins on the Led driver board (in which the power cord plugs in) - all seemed fine.
    I got a service manual for this model and tested the DC/DC converter by checking voltages on selected components. Every voltage was present where it should be. Service manual says that in this case a "Muffin" replacement is needed. This is the moment where I got stuck as I wasn't able to Google my way through it - till this day I have absolutely no idea what the "Muffin" is.

    Decided to just swap the mainboard instead of trying to find out the meaning of "Muffin". Even had an actual muffin during lookout for the board. Found one from 50" 755c, exactly the same board numbers.

    After installing it I was greeted by flashing green/Amber lights. "Firmware please" it said. Downloaded it from Sony website and flashed it - could see the status light change to dimming white, which - according to various places in the Net - means it is reading the firmware and installing it. After some time the TV resets and... Continues to flash green/Amber, this time with Android setup sound playing in the background. I can hear it reacts to the remote as well.
    It is not a backlight issue as the backlight works fine when mainboard is disconnected from the PSU, and there is no picture visible when flashing with torch.
    Green/Amber flash means panel Id error, which I guess maybe could be solved by choosing the correct panel Id in service mode - the problem is I have no picture and can't really do it blind.
    I've seen various threads about a corrupted Android update that caused this sets to fail this way. At this pont I am suspecting that the board I received from eBay has the 'bricked' soft on it, that doesn't 'want' to be overwritten.

    My questions to you are as follows:
    1. Is anyone able to explain what a "Muffin" is? Eeprom?
    2. If the board I received has a corrupted firmware on it, would it update over with fresh update from Sony website?
    3. Is there any reasonable way to make 1 properly working board out of the 2 I have? I suspect swapping the firmware is 'a bit' more complicated than transferring an iC containing it?

    What's my best shot now? Any help would be highly appreciated.
    Thanks for stopping by.
    Attached Files
    Last edited by mrsith; 11-28-2022, 12:46 PM.
    Tags: None
    #2
    Re: Sony KDL-55W755C - Dead

    Probably the EEMC chip on mainboard is dead, they only last so long.

    Comment

      #3
      Re: Sony KDL-55W755C - Dead

      Backup the contents of both EMMC’s from both boards, then flash the content from the original board to the new board with flying wires. No soldering needed.

      Comment

        #4
        Re: Sony KDL-55W755C - Dead

        Android versions carrys the name of a typical sweet, evidently your tv has got muffin version. Since this is an always on tv, a not booting tv is often one with damaged android. I have followed a thread on an italian forum that was by headache, also there a not booting one followed by mb replacement and no video with audio, ended up in carrying the giant tv to Sony assistance, they told to the owner they worked only with closed tv and an usb memory with correct firmware, i guessed they have secret key combinations/menus that carrys to the correct updating process that recognize the actual panel and synchronizes with the new main board..
        Finally i suggest you to try insert the sowftware usb key in with tv in standby, then keep press on key on local keyboard for 4-5 secs and watch if update starts, if the process is not successful retry it but with at least 14-15secs..
        bye..
        Last edited by Davi.p; 11-28-2022, 06:30 PM.

        Comment

          #5
          Re: Sony KDL-55W755C - Dead

          lol, if only someone could get that SECRET combination, but there is no such thing in the real world.
          Last edited by nomoresonys; 11-28-2022, 10:45 PM.

          Comment

            #6
            Re: Sony KDL-55W755C - Dead

            Originally posted by Davi.p View Post
            Android versions carrys the name of a typical sweet, evidently your tv has got muffin version.
            There was no Android version called Muffin (there was Cupcake but that's an ancient 2009 1.5 version which was never present in this TVs) and the service manual says about REPLACING the Muffin, so doesn't sound like a soft reinstall.

            Comment

              #7
              Re: Sony KDL-55W755C - Dead

              ^^^LOLOLOL, I believe you 1000%.

              Comment

                #8
                Re: Sony KDL-55W755C - Dead

                it is a coded name or a special version of android

                Comment

                  #9
                  Re: Sony KDL-55W755C - Dead

                  they were toying with the idea of calling android 6 muffin, but it's no secret or special conspiracy that needs a magic combination, VERY AMUSING concept tho.
                  Last edited by nomoresonys; 11-29-2022, 07:50 AM.

                  Comment

                    #10
                    Re: Sony KDL-55W755C - Dead

                    For anyone in the future who might be looking for this answer - Muffin doesn't mean Android. Sony calls that it's main SOC, trivialising it Muffin = CPU.

                    I did try the update hundreds of times with the same results. Ordered a programmer to dump and flash eMMC as suggested. It's about time lol.
                    Attached Files

                    Comment

                      #11
                      Re: Sony KDL-55W755C - Dead

                      You can't do Capleaker's suggestion because flow chart tells emmc erase and re install software, this doesn't mean copy a premade installation with a dump but a new installation maybe with a software installer by usb flash key, remember cpu has got in it some key codes.. them must be used for new installation.. this is what seems to me..

                      ps: is possible new software is copied at steps, like another tv i repaired, first bootloader copy by serial port, then usb installation..
                      Last edited by Davi.p; 11-30-2022, 04:26 PM.

                      Comment

                        #12
                        Re: Sony KDL-55W755C - Dead

                        Only the flow chart sez something, doesn’t mean automatically it has to be done that way. I’ve cut many flowcharts short and was surprised with the outcome that it actually did work copying the content from one board and load it to the identical other board. Even worked on an Android TV box. Given, it isn’t a guarantee to revive this like that, but worth a shot. Before I do the boot loader on a TTL and USB jazz, I prefer making a dump file and flashing that. However, you have to be very careful with that and know what you’re doing, because you can easily screw up a dump too, by not selecting proper chip parameters, etc.

                        Comment

                          #13
                          Re: Sony KDL-55W755C - Dead

                          You weren't able to read the faulty eMMC and had to read off a working one IIRC Capleaker.

                          Comment

                            #14
                            Re: Sony KDL-55W755C - Dead

                            Originally posted by CapLeaker View Post
                            Only the flow chart sez something, doesn't mean automatically it has to be done that way. I've cut many flowcharts short and was surprised with the outcome that it actually did work copying the content from one board and load it to the identical other board. Even worked on an Android TV box. Given, it isn't a guarantee to revive this like that, but worth a shot. Before I do the boot loader on a TTL and USB jazz, I prefer making a dump file and flashing that. However, you have to be very careful with that and know what you're doing, because you can easily screw up a dump too, by not selecting proper chip parameters, etc.
                            +1000, I have also seen this done before, and seen some done on youtube.

                            Comment

                              #15
                              Re: Sony KDL-55W755C - Dead

                              Yes, that is correct. It was the Dreamlink T1, first Android box with an EMMC I did. I even put larger EMMCs and different brands in there. I made a dump from a working one, then copied that to a different EMMC that I had in the junk pile and soldered that on to the non working one. MAC addressees etc were no problem and stayed the same as they were. I ended up fixing a few of these boxes and others too using the exact same method. Worked like a charm every time.
                              The problem with this is, you gotta know what you’re doing. So someone had the idea to read their router and didn’t select the chip proper (there were 2 versions on how the memory banks are laid out). Selected the wrong one, dumped the contents (no errors). Then he flashed the dump file back and now he got tons of errors during flashing back and of course the router doesn’t work no more, then wonders why.
                              Last edited by CapLeaker; 12-01-2022, 09:22 PM.

                              Comment

                                #16
                                Re: Sony KDL-55W755C - Dead

                                That flow chart was about replacing the CPU - I think only then it is necessary to follow exactly these steps.

                                I did some BIOS programming before but don't have experience with eMMC. Did some digging and it seems -quite- straightforward, but is there anything specific I should know? Or maybe some step by step how-to guide?
                                Would soldering the original eMMC to the new board do the trick? Not a fan of bga-like ICs at but least I'd know what I'm doing lol.
                                Last edited by mrsith; 12-02-2022, 06:27 AM.

                                Comment

                                  #17
                                  Re: Sony KDL-55W755C - Dead

                                  You can read my Dreamlink T1 thread. I did both, using flying wires to read and write from and to the EMMC, and I replaced the bad EMMC with a used and re flashed one. Its not as quite forward as it seems. Lots of pitfalls if its not done correctly.
                                  First tip is don't take a EMMC off, if you don't have to. Getting it off, isn't the problem. But getting it soldered back to the board, is the hard part. You need low temperature melting solder. Some use solder balls and a stencil, I didn't.
                                  Second tip is an oscilloscope to figure out where to get all your wires hooked up to the board to read / flash the EMMC without taking it off. This takes quite a bit of probing, measuring and verifying.
                                  Third tip is to get a digital microscope like Andonstar and put that on a large monitor, so you can see something.
                                  Take your time doing the work and double check everything. It looks easier than it is. I would only take the EMMC off or reflow it, if it doesn't communicate. Which is easy to figure out by measuring the data lines with the oscilloscope.

                                  Comment

                                    #18
                                    Re: Sony KDL-55W755C - Dead

                                    I'd stick the suspected faulty one in a socket and a RT809H to see if it was faulty.
                                    If it is then I see two options, swap your original eMMC which will require some skill as the BGA is small and needs replacing, or buy a preprogrammed one with the balls already on, so the hard work is done.

                                    Comment

                                      #19
                                      Re: Sony KDL-55W755C - Dead

                                      you don't need to stick the emmc into the RT809H in order to see if it is faulty. Just look at the data lines, clock, voltage etc. A dead emmc will not transfer any data at all.

                                      Comment

                                        #20
                                        Re: Sony KDL-55W755C - Dead

                                        Your previous post you say it takes time to find where to attach the wires. My way would be quicker and if it's faulty it has to come off anyway.
                                        There's more than one way to do things, it depends on the tools and skills on hand and time.

                                        Comment

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