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Sony KDL-46EX505 No T-con Voltage

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    Sony KDL-46EX505 No T-con Voltage

    Hi all,

    been asked to look at a friends old Sony which turns on ok, changes channels and has backlight and volume control etc. yet just displays grey, with a few streaky lines across the screen.

    A quick test revealed that the voltage across the T-Con cable connector(CN6151) on the PSU (G2) was missing, although the 3.3v 'T-CON_On' and 'T-CON_Vcc12v' were present at the connector which links to the main board (CN6150).
    As they live some distance away I took the PSU with me to see where the problem might lie.



    I'm presuming that the 3.3v needs to be connected to both the 'POWER_On' and 'T-CON_ON' in order to for the area in question on the board to stay 'live'?
    There is not a lot of circuitry between the two connectors, with a FET and a couple of transistors after the secondary of a transformer, but my concern is whether the PSU might be damaged with no load?

    I'm not a TV tech but want to know if there is likely to be any problem if I power the board up without any load?

    Enclosing the schematic and a couple of photos of the suspect area if anyone is interested
    Attached Files
    Last edited by Crystaleyes; 05-11-2022, 09:04 PM.

    #2
    Re: Sony KDL-46EX505 No T-con Voltage

    As a load, you can use car incandescent lamps, then checking the power supply will be more informative

    Comment


      #3
      Re: Sony KDL-46EX505 No T-con Voltage

      Originally posted by Crystaleyes View Post
      As they live some distance away I took the PSU with me to see where the problem might lie.

      I'm presuming that the 3.3v needs to be connected to both the 'POWER_On' and 'T-CON_ON' in order to for the area in question on the board to stay 'live'?
      you are correct about how to run the PCB as stand alone to have t-con 12 and other V to MB socket... but i think you took the wrong boards with you... the issue much at MB. or T-CON or panel.

      Comment


        #4
        Re: Sony KDL-46EX505 No T-con Voltage

        Originally posted by kasfamily View Post
        As a load, you can use car incandescent lamps, then checking the power supply will be more informative
        Yes. Nice one.

        Obvious really, but still didn't enter my head,

        thanks

        Comment


          #5
          Re: Sony KDL-46EX505 No T-con Voltage

          Originally posted by Diah View Post
          you are correct about how to run the PCB as stand alone to have t-con 12 and other V to MB socket... but i think you took the wrong boards with you... the issue much at MB. or T-CON or panel.
          You think so?

          Does the T-CON_ON signal not come to the PS board from the main board? Then surely it is the PSU board which powers the T-CON board?

          Haven't had time these last couple of days but intend to power up the PSU and see what readings come up.

          Comment


            #6
            Re: Sony KDL-46EX505 No T-con Voltage

            No you don't need a load to check unless you suspect it can't put out the required current.
            T-con are most often powered through the ldvs cable from the main to the t-con on one side of the cable.
            I assume no responsibility for any stupid suggestions I might post.

            Comment


              #7
              Re: Sony KDL-46EX505 No T-con Voltage

              Originally posted by dskall View Post
              No you don't need a load to check unless you suspect it can't put out the required current.
              Thanks.

              T-con are most often powered through the ldvs cable from the main to the t-con on one side of the cable.
              And I'm sure that there is some power in this cable as the T-CON board gets warm.
              There is a second thicker wired cable from the PSU to the T-Con and it is this which has no power.
              Hopefully should have time today to connect it up and test it further

              Comment


                #8
                Re: Sony KDL-46EX505 No T-con Voltage

                yep, when dealing with distance, always take the whole tv whenever possible.

                Comment


                  #9
                  Re: Sony KDL-46EX505 No T-con Voltage

                  It always helps to have good pictures.
                  I assume no responsibility for any stupid suggestions I might post.

                  Comment


                    #10
                    Re: Sony KDL-46EX505 How to test a T-CON board?

                    Originally posted by dskall View Post
                    It always helps to have good pictures.
                    For sure, but only having the one board with me didn't help.

                    Anyway, fired up the board and the T-CON connector voltages are present and correct at 12v, so it would indeed appear that I am looking at the wrong board.

                    I'll head back up to the TV in the next few days, but are there specific voltages which can be measured on the T-CON board to confirm whether or not it is working?

                    Comment


                      #11
                      Re: Sony KDL-46EX505 No T-con Voltage

                      vgl, vgh, vcom, vcc's
                      I assume no responsibility for any stupid suggestions I might post.

                      Comment


                        #12
                        Re: Sony KDL-46EX505 No T-con Voltage

                        Still haven't got back to the TV but considering there are a multitude of lines across a grey screen, judging by what I can find, it may be that the VDA/VSource voltage is missing.

                        If tht does turn out to be the case, any idea what might cause that to fail?

                        Comment

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