Hitachi TV 42hxt12u no display after LED Repair

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  • asda333
    New Member
    • Jan 2021
    • 8
    • United Kingdom

    #1

    Hitachi TV 42hxt12u no display after LED Repair

    Hi

    So I have this TV Hitachi 42hxt12u and I was experiencing the same problem which mrreeseburger showed a video about a faulty LED that had blown, as I could see image when shining light on tv which was not showing anything and checking with multimeter the voltage at the LED connector showed around 180 volts then went down to 117V and stayed there.

    I opened it up as shown in video and replaced the bulbs and they all work, which before 3 were blown.

    After closing the panels back the blue cover on the back of one of the t-con flex cable had come off and i glued it back on and placed in back in and a little fidgety but managed and turning the tv on and no display but lines so thought ok let me clean the contacts on the flex cable and socket and put it back on and it worked saw logo and everything, but there was this vertical line on the left side middle.

    So I cleaned out the contacts of the flex cable and saw the contacts of the flex cable one had snapped off and I had to use a very small tin foil folding and glued in place and glued it down the back and made sure there was contact between the short original contact and my new foil contact and placed it in the socket still didn't work and saw there was a short between the contacts with my quick fix tin foil contact and then tried again also had to remove excess glue until finally fit it in and made sure there was continuity from the socket to the end of the cable where the contacts were fine and untouched and that there was no short circuit.

    Putting it back in, I get no display only a lot of vertical lines, before only 1 vertical line now I get a lot of vertical lines.

    Also the tv has this issue of when turning on after a few seconds the display would go blank and then turn on again.

    I removed the tconn board and turned on again and the top i see slight marks of the vertical lines but they disappeared making me think it's residual thing.

    So now before the display showed logo and scanning channels but now no display only backlight which turns on then dims a little then stops.

    Would appreciate help on this.

    Below is a video of the current status of the TV when I turn it on, first one shows with the tcon board connected to main board and second one is tcon board disconnected from the main board.

    https://imgur.com/a/KchOs9X

    From beginning (27th second) to 15th second that's one video all that happens when I turn on my tv, it turns on then off then on again, second half is with tcon disconnected.

    I don't know how it happened, one day it's working, next day back light LED goes off and now after repairing the LED the tcon board goes.

    Thanks

    P.S Thanks to MrReeseyBurger for that great video on diagnosing bad faulty LED backlight strip and what to expect when measuring with multimeter.
    Last edited by asda333; 01-29-2021, 12:52 PM.
  • asda333
    New Member
    • Jan 2021
    • 8
    • United Kingdom

    #2
    Re: Hitachi TV no display after LED Repair

    Hi

    So after ordering a replacement T-Con board and then no display so I disconnected the t-conn board and with the power disconnected and hold the power button to drain and connect the tv again without tcon board to show glow without display then disconnect and reattach tconn board and the display should work, which it did but I still got this vertical lines pair of it on one side.

    But if I take a good cable from the previous board and replace one of the tcon cables it shows no display as if no tconn board connected even when i follow above procedure still no display no matter what.

    As if a specific cable will work with a specific board and specific cable pairs work together.

    So i replace the old cable and the display comes on with the stripe after following above procedure, same as with the supposed faulty t-conn board, only reason i was getting multiple stripes which i posted here as I didn't know of the above procedure because when i did fix cable as mentioned in original post display came with the same pair of lines.

    Image

    Last edited by asda333; 02-04-2021, 08:21 AM.

    Comment

    • asda333
      New Member
      • Jan 2021
      • 8
      • United Kingdom

      #3
      Re: Hitachi TV no display after LED Repair

      Now I am not getting any display only sounds, which after a while stopped too.

      When I turn TV, logo displays then tv turns off then back on again but no display.

      What's going on.

      Any help.

      Comment

      • neilc6
        Badcaps Legend
        • Nov 2015
        • 1550
        • Canada

        #4
        Re: Hitachi TV no display after LED Repair

        Random vertical lines are damaged panels. Sony tcon training manual pg 39 https://dokumen.tips/documents/sony-...ng-manual.html

        If you didn't replace all the backlights with new and turn down the backlight level, then the unrepaired LEDs are likely to fail.

        Comment

        • asda333
          New Member
          • Jan 2021
          • 8
          • United Kingdom

          #5
          Re: Hitachi TV no display after LED Repair

          Originally posted by neilc6
          Random vertical lines are damaged panels. Sony tcon training manual pg 39 https://dokumen.tips/documents/sony-...ng-manual.html

          If you didn't replace all the backlights with new and turn down the backlight level, then the unrepaired LEDs are likely to fail.
          Thanks for getting back.

          I only replaced the faulty LED's not the entire strip and tested each bulb to make sure they were working and closed.

          Everytime I turn tv on, the logo flashes and then screen goes blank and then goes on again but with no display.

          So with regards to the single line, it's probably a bad tab bond or bad drive IC.

          Anyways of fixing it.

          What could be problem of no display now but sound. Don't think it's LED back light as when you first turn on display comes up everytime but turns off and then turns back on again but no display and screen is completely dark.

          Thanks for assisting me on this.

          Comment

          • neilc6
            Badcaps Legend
            • Nov 2015
            • 1550
            • Canada

            #6
            Re: Hitachi TV no display after LED Repair

            I have repaired individual LEDs and have had more fail immediately after. You still have bad backlights though the panel is damaged.

            Comment

            • asda333
              New Member
              • Jan 2021
              • 8
              • United Kingdom

              #7
              Re: Hitachi TV no display after LED Repair

              Originally posted by neilc6
              I have repaired individual LEDs and have had more fail immediately after. You still have bad backlights though the panel is damaged.
              If the Backlights are damaged, wouldn't the backlight not turn on when I turn on the TV.

              The backlight turns on but after the tv turns off and on again and then no display but backlight turns on but dims down to darkness.

              Comment

              • asda333
                New Member
                • Jan 2021
                • 8
                • United Kingdom

                #8
                Re: Hitachi TV no display after LED Repair

                I'm back again trying to repair this TV and when I turn it on, the logo start up flashes with the strip line down the left side which I showed here. Single strip of 2 lines close together, it flashes and then goes black. This repeat every time I unplug it and plug it back. The switch doesn't turn the TV off.

                I replaced the tcon board, power supply board and all the led array strips for back light and the main board but it still flashes.

                The fact the power button doesn't work makes me think the main board is bad. As holding it down should switch it off.

                Regarda

                Comment

                • neilc6
                  Badcaps Legend
                  • Nov 2015
                  • 1550
                  • Canada

                  #9
                  Re: Hitachi TV no display after LED Repair

                  Not sure why you are wasting your time trying to repair a TV with a damaged panel. if you remove the panel and record the backlights flashing, you will be able to see which LEDs are not lighting up.

                  Comment

                  • asda333
                    New Member
                    • Jan 2021
                    • 8
                    • United Kingdom

                    #10
                    Re: Hitachi TV no display after LED Repair

                    All the back lights are lighting up as I replaced all the led strips.

                    Comment

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