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    Sony KD-55X8505 not able to start

    Sony KD-55X8505 plug it in, PFC starts up at 390VDC, DC/DC kicks on seem to supply mainboard with +12.7VDC.
    No led backlight, no supply to T-con...

    Any clue?

    #2
    Re: Sony KD-55X8505 not able to start

    do you get backlights with cable from powerboard to mainboard unhooked?

    Comment


      #3
      Re: Sony KD-55X8505 not able to start

      No, when PSU/MB harness disconnected, the PSU is kept in standby.
      It's not like the Samsung's when full backlight will be on when cable disconnect.

      Comment


        #4
        Re: Sony KD-55X8505 not able to start

        So what is ps-on, bl-on? Did you heat up processor?
        I assume no responsibility for any stupid suggestions I might post.

        Comment


          #5
          Re: Sony KD-55X8505 not able to start

          Originally posted by dskall View Post
          So what is ps-on, bl-on? Did you heat up processor?
          Heat up processor on MB ?

          BL_ON is low constantly. Independent of MB. PS_ON goes high and PSU starts up.

          Do you have the service manual or perhaps how the start-up sequence should be ?

          Also, no led activity at all. "Smells MB" ??

          I tried to force BL_ON high to +3V3 (first disconnect that wire to MB) but there is no led outputs wakes up...
          Last edited by PowerAmpFreak; 06-22-2022, 11:02 AM.

          Comment


            #6
            Re: Sony KD-55X8505 not able to start

            Originally posted by PowerAmpFreak View Post
            No, when PSU/MB harness disconnected, the PSU is kept in standby.
            It's not like the Samsung's when full backlight will be on when cable disconnect.
            as long as you're sure, I had an old kdl sony from 2010 that does same as samsung, so it's NOT just the samsungs that self test in that manner, not saying you're wrong, just saying it isn't only samsungs that have that feature.
            Last edited by nomoresonys; 06-22-2022, 11:06 AM.

            Comment


              #7
              Re: Sony KD-55X8505 not able to start

              Originally posted by nomoresonys View Post
              as long as you're sure, I had an old kdl sony from 2010 that does same as samsung, so it's NOT just the samsungs that self test in that manner.
              I believe you, but in this case MB has to pull PS_ON to high at least to power up the power. It seems to be the case also for the BL_ON, but I cannot at all be sure without a service manual or other advice.

              Comment


                #8
                Re: Sony KD-55X8505 not able to start

                would probably have to test it as stand alone, using resistors, Diah knows a lot about that process, he helped me test my sony but I forgot the procedure, the memory is the first to go.

                Comment


                  #9
                  Re: Sony KD-55X8505 not able to start

                  Anyone know how to test the PSU standalone ?

                  Comment


                    #10
                    Re: Sony KD-55X8505 not able to start

                    yours TV android. so MB need 12V always on like any android STB box / reciever.......to test the PSB als stand alone. you need external stepdown circuit but in case you don't have one. you can use the MB stepdown circuit. you need to unplug the socket between PSB & MB from MB side.. and just bring one wire from PSB 12V which STB and feed it to the assigned pins at MB socket. look after DC to DC on MB you will find the 3.3V there.. use it to power the PSB as you like.. don't forget BL_ON need DiM pin active too.

                    Comment


                      #11
                      Re: Sony KD-55X8505 not able to start

                      Originally posted by Diah View Post
                      yours TV android. so MB need 12V always on like any android STB box / reciever.......to test the PSB als stand alone. you need external stepdown circuit but in case you don't have one. you can use the MB stepdown circuit. you need to unplug the socket between PSB & MB from MB side.. and just bring one wire from PSB 12V which STB and feed it to the assigned pins at MB socket. look after DC to DC on MB you will find the 3.3V there.. use it to power the PSB as you like.. don't forget BL_ON need DiM pin active too.
                      In this set, it appears MB only needs 3V3 as STBY.
                      I did disconnect cable between PSU and MB on MB side and pulling PS_ON and BL_ON to 3V3, but I never did with DIMMER so will try again.

                      New try:
                      BL_ON
                      PS_ON
                      DC_DIM
                      all connected to 3V3 does not generate any backlight.

                      Also, 12V T-CON is not on.
                      Last edited by PowerAmpFreak; 06-26-2022, 08:04 AM.

                      Comment


                        #12
                        Re: Sony KD-55X8505 not able to start

                        a backlight tester would be handy in this instance, about 20 bucks on ebay or amazon.

                        Comment


                          #13
                          Re: Sony KD-55X8505 not able to start

                          always photo on the whole back and the PSU socket pins map will be helpfull if t-CON recieve 12V from PSU direct or via MB. if its from PSU then should have pins like T-CON on
                          Originally posted by PowerAmpFreak View Post
                          In this set, it appears MB only needs 3V3 as
                          first post you wrote 12V only come to MB so the MB have DC/DC stepdown to producse 3.3V which you take it for test
                          Last edited by Diah; 06-26-2022, 08:51 AM.

                          Comment


                            #14
                            Re: Sony KD-55X8505 not able to start

                            Attach pictures.

                            12V T-Con is coming directly from PSU.
                            PSU generates +63V to dual boost converters to generate led backlight voltage. But boost converters are off.
                            No led is flashing.
                            PSU generates PFC voltage of 393V and 12V output is 12.7V.
                            STBY supply is 3.5V
                            Attached Files
                            Last edited by PowerAmpFreak; 06-26-2022, 09:02 AM.

                            Comment


                              #15
                              Re: Sony KD-55X8505 not able to start

                              this tv is 8 years old or so, I would suspect backlights.

                              Comment


                                #16
                                Re: Sony KD-55X8505 not able to start

                                yours photo

                                so now its clear you have 3.3V STB.
                                STB- with Power On you will have REG12V this must be inplace to do further
                                STB with T_CON ON you will have T-CON VCC12V
                                STB with BL_ON will post BL

                                PM Dimmer need R as its low or high

                                Comment


                                  #17
                                  Re: Sony KD-55X8505 not able to start

                                  Originally posted by Diah View Post
                                  yours photo

                                  so now its clear you have 3.3V STB.
                                  STB- with Power On you will have REG12V this must be inplace to do further
                                  STB with T_CON ON you will have T-CON VCC12V
                                  STB with BL_ON will post BL

                                  PM Dimmer need R as its low or high
                                  Todays test:

                                  3V3 STB connect to PS_ON will make REG12V @ 12.7VDC
                                  3V3 STB connect to TCON_ON will make T-CON @ 12.7VDC
                                  3V3 STB connect to BL_ON does not change anything.
                                  3V3 STB connect also to DC_DIMMER does not change anything.
                                  I would suspect the boost converters to go active? At this point I have not applied anything to PWM DIMMER points.
                                  Last edited by PowerAmpFreak; 06-27-2022, 09:46 AM.

                                  Comment


                                    #18
                                    Re: Sony KD-55X8505 not able to start

                                    Originally posted by PowerAmpFreak View Post
                                    Todays test:

                                    3V3 STB connect to PS_ON will make REG12V @ 12.7VDC
                                    3V3 STB connect to TCON_ON will make T-CON @ 12.7VDC

                                    3V3 STB connect to BL_ON does not change anything.
                                    3V3 STB connect also to DC_DIMMER does not change anything.
                                    I would suspect the boost converters to go active? At this point I have not applied anything to PWM DIMMER points.
                                    yours PSU look fine.. put all sockets as it should and capture the V on BL sockt between each group of LED+ & LED- at start up ( boot ) check the high and low messurments to compare the groups reading after you finish the test.

                                    Comment


                                      #19
                                      Re: Sony KD-55X8505 not able to start

                                      Originally posted by Diah View Post
                                      yours PSU look fine.. put all sockets as it should and capture the V on BL sockt between each group of LED+ & LED- at start up ( boot ) check the high and low messurments to compare the groups reading after you finish the test.
                                      During boot, the maximum voltage applied from led driver is 63V (two outputs). I think I could power up each led group by a separate powersupply capable of 120V current limited ?
                                      Attached Files
                                      Last edited by PowerAmpFreak; 06-27-2022, 10:15 AM.

                                      Comment


                                        #20
                                        Re: Sony KD-55X8505 not able to start

                                        Originally posted by PowerAmpFreak View Post
                                        During boot, the maximum voltage applied from led driver is 63V (two outputs). I think I could power up each led group by a separate powersupply capable of 120V current limited ?
                                        you have BL_error on the sockt. if its goes high at boot then you need to be ready for the hard work BL LED

                                        Comment

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