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Help diagnosing laptop ASUS X556UJ_MB REV 2.0 motherboard

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    #1

    Help diagnosing laptop ASUS X556UJ_MB REV 2.0 motherboard

    Hello everyone, I have this Asus model X556UA that when plugged in I get the white light but nothing happens when pressing the power button. I've been looking into it following the power sequence and found out that the power button is sending the signal to the EC (PWR_SW#) but the EC is not sending the PM_PWRBTN# to the PCH (it always stays at 3.3V). I'm stuck here and don't know what else can I do, maybe I can get some help. I've seen that this could mean that the PCH is dead but I don't know how I can confirm this. Also this may not be important but when plugged in, the PCH/CPU (they go together in this motherboard) gets warm.

    Link to schematic - https://www.badcaps.net/forum/troubl...-3-1-schematic
    Tags: None
    #2
    What is the current draw on your dc supply?
    SOC(PCH+CPU) shouldnt get warm in off state. May be the m/b is partially on .
    Measure voltage & Resistance to GND on all coils.
    Share your measurements.

    Comment

      #3
      Originally posted by mcplslg123 View Post
      What is the current draw on your dc supply?
      SOC(PCH+CPU) shouldnt get warm in off state. May be the m/b is partially on .
      Measure voltage & Resistance to GND on all coils.
      Share your measurements.
      I'm getting 117 mA current draw when plugging in the power supply. It stays the same when pressing the button.

      Reading on the coils are the following:

      +5VSUS (PL8702): 5 V / 14 KΩ
      +1.0VSUS (PL8301): 1.391 V / 227 Ω
      +1.35SVG (PL9300): 1.024 V / 46 Ω
      +3VADSWO (PL8701): 3.320 V / 6 KΩ
      +VCCSA (PL8103): 1.047 V / 11 Ω
      +VCCCORE (PL8102): 0 V / 6 Ω
      +VCCGT (PL8101): 0 V / 6.5 Ω
      Battery coil (PL8901): 0.2 V / 100 KΩ

      Comment

        #4
        I think you mixed up voltage reading on +1.0VSUS & +1.35SVG.
        +12VS present?
        ALL_SYS_PWRGD-present?
        +1.8VS present?
        +VCCIO present?
        +VCCST present?
        +1.2V present?

        Report back on these findings.

        Comment

          #5
          Originally posted by mcplslg123 View Post
          I think you mixed up voltage reading on +1.0VSUS & +1.35SVG.
          +12VS present?
          ALL_SYS_PWRGD-present?
          +1.8VS present?
          +VCCIO present?
          +VCCST present?
          +1.2V present?

          Report back on these findings.
          Yes you are right, here are the corrections:

          +5VSUS (PL8702): 5 V / 14 KΩ
          +1.0VSUS (PL8301): 1.024 V / 46 Ω
          +1.35SVG (PL9300): 1.391 V / 227 Ω
          +3VADSWO (PL8701): 3.320 V / 6 KΩ
          +VCCSA (PL8103): 1.047 V / 11 Ω
          +VCCCORE (PL8102): 0 V / 6 Ω
          +VCCGT (PL8101): 0 V / 6.5 Ω
          Battery coil (PL8901): 0.2 V / 100 KΩ

          +12VS present -> YES
          ALL_SYS_PWRGD -> YES
          +1.8VS present -> YES
          +VCCIO present -> YES
          +VCCST present -> YES
          +1.2V -> MISSING: I'm getting weird readings like 0.4 V and 0.6 V

          Could the on board RAM be the problem? Thanks for your answers!

          Comment

            #6
            PU8601 is the pwm controller for RAM voltage output.You should get 1.2V on PL8601. Check voltage again here to be sure.
            Measure voltage on S3/S5/TON/VCC of PU8601(after power on.
            Very likely problem may be the resistor connected on TON pin.Make sure PR8607 is 560K.
            S3/S5 are enables for ram IC and since you have almost all major rail running,they cant be missing.
            Hence my doubt goes towards PR8607 .

            PS:Lets not doubt the onboard ram for now.First lets see whether the PWM ram ic is functioning well or not.

            Comment

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