Sony KDL-55HX825

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  • Hauke
    Senior Member
    • Jan 2017
    • 77
    • Germany

    #1

    Sony KDL-55HX825

    Hello,


    When I try to start my Sony Bravia KDL-55HX825 it lights up for about a second and then shuts down and shows the blinking code 4.

    The Sony Logo at the bottom of the TV and the background light flash up very shortly. But two times the TV displayed the Sony Logo shortly on the screen before it shut down.

    I already measured some things:
    • The main psu seems to work. 3v3 is alive and 12V gets active when I pull POWER_ON high
    • The second psu (for the backlight) generates about 60V when the TV starts and decreasingly falls to 0V after a second
    • BL_ERR is about 0.7V in standby, then goes down to 0V, up to 3V and down to 0V (couldĀ“t check with oscilloscope yet)
    • When I add a resistor to pull BL_ERR high or low nothing changes
    • When the TV shuts down POWER_ON at the psu gets low and 12V is off, which deactivates the second psu
    • The backlight LED strips are ok. I already disassembled the whole panel just to see that there was no failure


    I found the schematics for the psu and the service manual online. I attached it to this thread.

    At the moment I don't know what to check next. Maybe someone had the same problem some time ago?

    Greetings from Germany,
    Hauke
    Attached Files
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Sony KDL-55HX825

    Can we see good clear pictures of the whole backside of the TV showing all the boards and then the pictures of each board?
    So did you check page 18 and the flow chart for the 4 TIMES Blinking (Balancer error) per service manual page 69?
    Last edited by budm; 01-10-2018, 02:27 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

    • Hauke
      Senior Member
      • Jan 2017
      • 77
      • Germany

      #3
      Re: Sony KDL-55HX825

      Thank you for your answer.

      I attached the pictures to this post.

      Yes I went through the flow chart.
      But now I would have to change some boards to find the failure.
      At the moment I don't want to order new boards because they are expensive and it would take 3-4 weeks delivery time (To Germany).

      I rather prefer to find the damage and repair the faulty board by myself.
      I had luck with many other monitors and TVs before.
      But this device is more complex and it would take a long time to go though the whole schematics.

      Is there an easy way to bypass the failure detection at the start?
      I think if the TV would stay on at startup, troubleshooting would be much easier.


      I think my next step is to go through the LED driver.
      Am I right with the presumption that the LED Driver just gets about 60V input, an enable signal, and PWM signals from the TCON for every single LED strip?
      I know, that the LEDs are arranged in arrays of 10 LEDs per string.
      There are six 6-channel BD9422EFV LED driver ICs on the board. (data sheet: https://cdn.badcaps-static.com/pdfs/...3152ef0dda.pdf)
      It looks like there are 4 channels used of each IC. So I get a sum of 10 LEDs * 6 * 4 = 240 LEDs.
      My idea is to power the LED driver with an external power supply and put a high power LED to each output.
      Then I would put the same pwm signal to all inputs.
      If the output differs I know that there must be a failure.
      Do you think this would work?

      Edit:
      Or maybe I can just use resistors for the output load. Since the ICs are constant current drivers the voltage will be lower and the load of my psu decreases?

      Edit 2:
      Ok I looked in the service manual again.
      It seems that there are also some other connections to the T-Con like: BL_TYPE, REF, FAIL, LED_ON, LD_STDBY, 12V.
      So I think my idea will not work...
      I read in another forum that someone had nearly the same problem.
      He solved it with changing the T-Con. Can this really be a T-Con issue?
      Attached Files
      Last edited by Hauke; 01-11-2018, 03:17 AM.

      Comment

      • uiticus
        New Member
        • Jan 2018
        • 2
        • United States

        #4
        Re: Sony KDL-55HX825

        I had the same problem with the Sony KDL-55NX720. The set shuts off and displays 4 blinking lights. Replacing the T-con board solved the problem.

        Comment

        • budwich
          Badcaps Legend
          • Jul 2015
          • 3097
          • Canada

          #5
          Re: Sony KDL-55HX825

          check any fuses that might be on the tcon

          Comment

          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #6
            Re: Sony KDL-55HX825

            If replacing the T-CON board fix the 4-blink problem then the service manual is wrong then.
            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

            • Hauke
              Senior Member
              • Jan 2017
              • 77
              • Germany

              #7
              Re: Sony KDL-55HX825

              Ok I will go to the tcon board now.
              Until now I know, that when I disconnect the tcon power supply the TV blinks 5 times.

              I will check the fuses the board now!

              Comment

              • Hauke
                Senior Member
                • Jan 2017
                • 77
                • Germany

                #8
                Re: Sony KDL-55HX825

                I checked the fuses:
                • F8001
                • F8002
                • F8101
                • F8102

                They are all at 0 ohms.

                I think I should check the ISL24835 regulator now.

                Edit:
                I added better pictures of the tcon board.
                Attached Files
                Last edited by Hauke; 01-11-2018, 10:56 AM.

                Comment

                • freakaftr8
                  Badcaps Legend
                  • Oct 2012
                  • 3743
                  • USA

                  #9
                  Re: Sony KDL-55HX825

                  I had this problem and changing out the led driver board for the local dimming system solved my problem. One of the BD9422EFV on the LED driver board was faulty. If you did this connect one LED string at a time from the driver board you may see that the picture comes up with 1 section not working. I was able to monitor the output voltages at 1 point and noticed that the LED driver circuit was not putting out voltage to one string. Somewhere I measured a direct short in the driver BD9422EFV.
                  Did I leave the soldering iron on?

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Sony KDL-55HX825

                    So you said you did look at the flow chart and the Voltages are OK per chart?
                    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

                    • Hauke
                      Senior Member
                      • Jan 2017
                      • 77
                      • Germany

                      #11
                      Re: Sony KDL-55HX825

                      Originally posted by freakaftr8
                      I had this problem and changing out the led driver board for the local dimming system solved my problem. One of the BD9422EFV on the LED driver board was faulty. If you did this connect one LED string at a time from the driver board you may see that the picture comes up with 1 section not working. I was able to monitor the output voltages at 1 point and noticed that the LED driver circuit was not putting out voltage to one string. Somewhere I measured a direct short in the driver BD9422EFV.
                      Thanks, I will try this. When I try to start the TV the backlight shows up only in the bottom middle of the screen for a very short time.

                      Originally posted by budm
                      So you said you did look at the flow chart and the Voltages are OK per chart?
                      My problem is, that the voltage is jumping. First from standby (0.7V) to 0V, up to 3V and again down to 0V. The flowchart says now I have to change the G, B or LED driver board. Since all of them are expensive I would rather get more into detail to find the failure part.

                      BTW:
                      I found someone on eBay who is selling the mainboard and LED driver board for about 50€ from a 46" TV with broken panel. I think I will buy this. If both boards doesn't bring the TV up to life, it can only be the tcon, right?

                      Comment

                      • freakaftr8
                        Badcaps Legend
                        • Oct 2012
                        • 3743
                        • USA

                        #12
                        Re: Sony KDL-55HX825

                        Yes it could be the tcon as it interprets signals from mainboard where to light up the panel with local dimming. Could be is not sending the LED driver board the proper signals there could be a shutdown as well. As in a mis communication error between the 2 boards.

                        However sense you are seeing some form of backlight come on, The area that should be lit up the most upon turn on would be the middle of the screen where the Sony logo shows.
                        Did I leave the soldering iron on?

                        Comment

                        • Hauke
                          Senior Member
                          • Jan 2017
                          • 77
                          • Germany

                          #13
                          Re: Sony KDL-55HX825

                          Ok, that makes sense now.

                          I measured all outputs and inputs on the led driver. Found no shorts, everywhere at least 5M ohm.
                          Then I found a sticker on the LED driver board. There is written „13662231671“ and „2017 03 21“. May the second line be the production date? If yes then the LED driver was already replaced by someone before.

                          Comment

                          • Hauke
                            Senior Member
                            • Jan 2017
                            • 77
                            • Germany

                            #14
                            Re: Sony KDL-55HX825

                            Hey guys, what do you think about this?
                            At a closer look to the T-Con board I found this thermal discoloration around the IC.
                            I can't find the data sheet of this IC. I think it must be a DC-DC converter.
                            Attached Files

                            Comment

                            • zomi
                              Badcaps Veteran
                              • Nov 2011
                              • 505

                              #15
                              Re: Sony KDL-55HX825

                              try taking out both the power boards
                              and going over all the main solder joints
                              I did this on 2 sony's and they are both working fine now
                              and being run hard as well with, with no issues.
                              Its a cheap fix and rules out any cold solder issues on the psu side.

                              Comment

                              • Hauke
                                Senior Member
                                • Jan 2017
                                • 77
                                • Germany

                                #16
                                Re: Sony KDL-55HX825

                                Thank you all for your help!
                                The TV is back to life now. The problem was the mainboard.
                                I got a mainboard from a KDL-46HX825. After flashing new firmware it worked!

                                Comment

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