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    Asus VW246H not turning on

    It's an old LCD monitor, that suddenly is not turning on.
    I have tried a couple of things and I have realized, that if I don't plug in the display ribbon cable from the logic board, the monitor turns on, back light turns on, stays on until checks for signal, than as the power LED turns from blue to red, the back light goes out. It seems like the logic board, does what it suppose to do.
    If I plug in the display ribbon cable, nothing happens, completely dead.
    The panel is shorted?

    #2
    Re: Asus VW246H not turning on

    Originally posted by tibimakai View Post
    If I plug in the display ribbon cable, nothing happens, completely dead.
    The panel is shorted?
    Which display ribbon? The one between the logic board and the T-con board (the thin long board that runs on top of the monitor and is usually under a metal shield.)
    If yes, that's the t-con board. Not uncommon for MLCCs (multi-layer ceramic caps) to go shorted on it. Typically, though, the t-con has a fuse, which should blow and allow the monitor to turn on (but with a white screen usually.)

    At this point, some pictures of the monitor's boards would help. Post one pictures showing how all of the boards are connected, as well as some individual pictures of the boards.

    Comment


      #3
      Re: Asus VW246H not turning on

      Yes, that ribbon.
      You are saying, that an MLCC could be shorted?
      So there is a T-con board? I have never repaired one like this before.
      Usually power supply issues, transformers, or CCFL tubes.
      Thanks for the idea. I will look into it, and I will take some pictures.

      Comment


        #4
        Re: Asus VW246H not turning on

        Originally posted by tibimakai View Post
        You are saying, that an MLCC could be shorted?
        So there is a T-con board?
        Yes and Yes.
        The t-con board is usually attached to the TFT panel on most monitors (very few have it as a separate board.) Typically, the T-con is located on the top of the monitor, under its own metal shield.

        Originally posted by tibimakai View Post
        I have never repaired one like this before.
        T-con issues are not as common as backlight / caps / power supply, but do happen every once in a while. My 3rd and 4th monitors I had to repair (for an friend some years ago) both had shorted MLCCs on the t-con. Took a while to get them fixed, as I was literally starting my quest in LCD repair. But in the end, that time I took paid off, as I was able to understand and fix many monitors afterwards.

        Comment


          #5
          Re: Asus VW246H not turning on

          It's been a while, since I have fixed a TV. I have stopped, because it's not worth it anymore.
          Mostly Onkyos I'm repairing these days, but it is not much money in that either, and they sell very slow.

          Comment


            #6
            Re: Asus VW246H not turning on

            I have found only one capacitor, that was showing 22 Ohm across it.
            I have also measured the same resistance, next to it(left) on the 0 Ohm resistor as well. It is hard to tell, if they are in parallel, but I don't believe that they are.
            An overall picture and than, from left to right.
            It's been a while, since I have posted a repair attempt and this is my first time, using the Note 8 for pictures. They are very good pictures, right?
            Attached Files
            Last edited by tibimakai; 02-02-2019, 06:56 PM.

            Comment


              #7
              Re: Asus VW246H not turning on

              Hard to day if that reading is normal or not (though I think usually low resistance readings like that aren't a good thing.)

              So check the following resistances to ground, first:
              5V1
              DAVDD1
              VGH1
              VGHC1
              YVEE1
              V33
              V1-V14 test points (where you show that 22 Ohm resistance is)
              VPP1

              Post what results you get here.

              Originally posted by tibimakai
              It's been a while, since I have posted a repair attempt and this is my first time, using the Note 8 for pictures. They are very good pictures, right?
              Yes, they are indeed. I'm surprised actually, as most phone pics tend to have poor focus. Not the case here.

              Comment


                #8
                Re: Asus VW246H not turning on

                Here they are:
                5V1= 2 KOHM
                DAVDD1= 1.1 KOHM
                VGH1= 66.7 KOHM
                VGHC1= 4.1 KOHM
                YVEE1= 4 KOHM
                V33= 0.9 KOHM
                V1= 1.1 KOHM
                V2= 1.06 KOHM
                V3= 0.88 KOHM
                V4= 0.83 KOHM
                V5= 0.8 KOHM
                V6= 0.74 KOHM
                V7= 0.68 KOHM
                V8= 500 OHM
                V9= 445 OHM
                V10= 363 OHM
                V11= 319 OHM
                V12= 261 OHM
                V13= 61 OHM
                V14= 21 OHM
                VPP1= 24.7 KOHM
                I'm no expert, but to me, it seems like, there is a big drop, from V12 to V13.
                Everything else seems OK, to me, at least.

                Comment


                  #9
                  Re: Asus VW246H not turning on

                  Originally posted by tibimakai View Post
                  Here they are:
                  ...
                  V12= 261 OHM
                  V13= 61 OHM
                  V14= 21 OHM
                  VPP1= 24.7 KOHM
                  I'm no expert, but to me, it seems like, there is a big drop, from V12 to V13.
                  Everything else seems OK, to me, at least.
                  V1 through V14 are for the TFT Gamma voltages (i.e. used for color levels).

                  Yes, V13 and V14 indeed look odd. Though, to be completely honest, I'm not sure if that is normal or not, as Gamma voltages are one thing I never really paid much attention to in the past in my repairs. I hope budm or someone equally knowledgeable sees this, as they might know better.

                  That said, generally my intuition is that if you see a low resistance reading across any MLCC / ceramic capacitor on the t-con of an LCD monitor, then the only way to know it's not shorted is to remove it and check its resistance outside of the circuit. Do that until all caps with low resistance caps have been removed and checked. Of course, save the removed caps, as they might be fine and could be put back on the t-con if they are OK.

                  Comment


                    #10
                    Re: Asus VW246H not turning on

                    I will remove some capacitors, in the weekend and I will be back, with the result. It would be nice, if I could unplug the screen itself from the board, to exclude that.

                    Comment

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