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Waterdamaged Asus N56VB - no power

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    #1

    Waterdamaged Asus N56VB - no power

    Laptop type : N56VB-S4061H
    The motherboard type is : N56VM Rev 2.3 GT740M

    Yesterday my girlfriend dropped a glass of water (few cc) on my keyboard.
    My laptop directly switched off and would not power on anymore. No leds would go on.
    Also when I removed the power cord from 220V, plugged it back it, it would not power on anymore.

    So, I directly removed the motherboard from the laptop, and discovered water on it. Removed it, and dried all the laptop parts with a hairdryer.

    Today I picked up my multimeter from home, and the power supply still supplied 19 Volt.

    Also when I plugged it in the power jack, the plug which would go into the motherboard, gave 19 Volt. But, when I plugged it into the motherboard, without anything connected, the voltage dropped instantly. I needed to deplug the power supply from 220V, and reinsert it again, without connected to the mobo, to get 19V again.

    I suspect, that a component has been broken, because of the short, caused by the water damage.

    But, it is hard to troubleshoot, when there is no voltage on it, to follow.
    What can I measure, to begin with, to find the cause, and solution.

    Motherboard, are for sale on ebay for $140 , but it will take a long time to be delivered to The Netherlands.
    Tags: None
    #2
    Re: Waterdamaged Asus N56VB - no power

    Post some high resolution picture of the motherboard and circle the spot where you found water.
    Check for a short at the power jack between + and ground.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment

      #3
      Re: Waterdamaged Asus N56VB - no power

      I cannot remember exactly where it was, it was at the side directly towards the motherboard somewhere in the middle.

      There was no short in the power jack, when the connector of the power jack, was not connected to the motherboard. Somehow, in the beginning I measured a resistence of a few MOhms.

      When the power jack, is not connected to the motherboard, the resistence between ground and + is 36,7 kOhm.

      Comment

        #4
        Re: Waterdamaged Asus N56VB - no power

        the only solution is to examine the motherboard with a strong magnification, a lens or a stereoscope. Many components such as resistors, are oxidized on the weld that it's hard to see . Each oxidized component , must be unsoldered and tested. Otherwise, the motherboard may start again but without removing the oxide could again be damaged.

        Comment

          #5
          Re: Waterdamaged Asus N56VB - no power

          Check for a short to ground on the AC_BAT_SYS line. There are many points where you can take a mesurement, for example on the current sense resistor I squared in red.
          Attached Files
          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

          Comment

            #6
            Re: Waterdamaged Asus N56VB - no power

            inject 10-19V to adapter connector to see heating/burn of failed component

            Comment

              #7
              Re: Waterdamaged Asus N56VB - no power

              My approach with water damaged boards it's different, because I think that if some particular components are disconnected (some pins dc/dc converter, etc) this could cause for example damage to a mosfet. If it's possible, in my opinion, is better an accurate examination of the motherboard than try to power it on.

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                #8
                Re: Waterdamaged Asus N56VB - no power

                Tomorrow, I will buy the same laptop with defective keyboard for 100 Euro, and do some comparances later on.

                Thanks for your input, when I have found the cause and solution, I will post it here.

                Comment

                  #9
                  Re: Waterdamaged Asus N56VB - no power

                  Worse, if some buck converter's top side MOSFET are shorted, (or any other regulator in fact), the 19V will be applied directly on components which expect 3.3V or lower for example. One of them is the CPU, and CPU buck converter's MOSFET do get shorted sometimes. You shouldn't inject more than 1.2V at first to see if the CPU/GPU or any other sensitive component gets hot.
                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                  Comment

                    #10
                    Re: Waterdamaged Asus N56VB - no power

                    high side mosfets make short to ground on adapter?

                    Comment

                      #11
                      Re: Waterdamaged Asus N56VB - no power

                      Well not directly, I was only saying injecting high voltage like this could be an issue. You could think there is a short to ground since the CPU/GPU show low resistance to ground. But in this case if you plug the power adapter in, the component may die already.
                      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                      Comment

                        #12
                        Re: Waterdamaged Asus N56VB - no power

                        short 0-2ohm, gpu 6+ ohm, CPU 11+ ohm

                        Comment

                          #13
                          Re: Waterdamaged Asus N56VB - no power

                          i need bios.bin file for the asus n56vb can someone help me ?

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