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Asus GL702VS No charge, unstable GPU power

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    Asus GL702VS No charge, unstable GPU power

    First post here, second if you count the introduction thread, so don't hesitate to tell me if I'm doing something wrong.

    Bought a used Asus GL702VS which had been sitting for a while so it arrived with a dead battery. Plugging in the charger it came back to life and I didn't notice any problems with the computer. I also used it running on battery for 1-2 hours. I then played around with undervolting the CPU with the charger connected when a 10uF MLCC shorted AC_BAT_SYS. After removing the short, battery won't charge and the GPU has power limitations. I suspect that these are 2 different problems and I'm first going to focus on the charge issue.

    GPU: While running Furmark GPU draws 110W for 10 seconds and then fluctuates between 110W and 45W every 4-5 seconds with a fixed interval. GPU Shark says it limits the performance due to power. Thermals are good.

    Battery: Doesn't charge at all. It will run on battery and HWiNFO will read acceptable charge rate, capacity and wear level. Voltage is stuck at 15.2V. Charge rate goes to 0 when charger is plugged in and nothing else changes. Battery led glows orange with the battery connected or disconnected. Also runs on charger with or without battery.

    Charge IC is bq24780S https://cdn.badcaps-static.com/pdfs/...91533e0300.pdf
    I haven't found a schematic for GL702VS but charge circuit is basically the same as the HPB in this thread. https://www.badcaps.net/forum/showthread.php?t=90356

    I've measured all MOSFETs in circuit that are related to charge IC and I can't find anything useful. I've taken voltages at charge IC with charger connected and apart from a low HIDRV my untrained eyes can't see anything that stands out. Voltage at battery terminal is 0.8V with charger and no battery. I'm going to replace both charge MOSFETs as well as the charge IC but it will take a couple of days until they arrive. In the meantime I would really appreciate any help I can get.

    Pin ------- Voltage
    ACN ------ 19.2
    ACP ------ 19.2
    CMSRC -- 19.7
    ACDRV --- 19.7
    ACOK ----- 6
    ACDET ---- 2.69
    IADP ------ 0.06
    IDCHG ---- 0.016
    PMON ----- 0
    PROCHOT - 0
    SDA ------- 3.27-3.83
    SCL -------- 3.27-3.83
    CMPIN ----- 0.26
    CMPOUT --- 6
    BATPRES -- 0
    TB_STAT -- 0.025
    BATSRC --- 14.5
    BATDRV ---- 14.5
    SRN -------- 14.5
    SRP -------- 14.5
    ILIM -------- 0.78
    GND -------- 0
    LODRV ----- 0
    REGN ------- 6.05
    BTST ------- 14.2
    HIDRV ----- 14.5
    PHASE ----- 4.5
    VCC -------- 19.4
    Last edited by Elektronror; 02-05-2021, 10:58 AM.

    #2
    Re: Asus GL702VS No charge, unstable GPU power

    Shorted DC-in MOSFET. First one, PQ8900 according to GL702VSK boardview.
    Last edited by piernov; 02-05-2021, 10:55 AM.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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      #3
      Re: Asus GL702VS No charge, unstable GPU power

      If that were the case it shouldn't turn on with charger only, right? I was a bit unclear on that part.

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        #4
        Re: Asus GL702VS No charge, unstable GPU power

        You can easily confirm the short by Measuring the Mosfets S-D-G in Ohms Mode. Should be at least KiloOhms usually
        FairRepair on YouTube

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          #5
          Re: Asus GL702VS No charge, unstable GPU power

          Depends, very often it'll still turn on if this DC-in MOSFET is shorted (current can flow through the shorted MOSFET and through the body diode of the other MOSFET). If the other DC-in MOSFET was shorted it wouldn't turn on (current would be blocked by the other MOSFET in reverse).
          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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            #6
            Re: Asus GL702VS No charge, unstable GPU power

            Q8900 is shorted. I knew from reading other threads that people here are quick but this was just insane. Really appreciate the help. Not quite sure why I didn't measure this one but there you go.

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              #7
              Re: Asus GL702VS No charge, unstable GPU power

              Originally posted by piernov View Post
              Depends, very often it'll still turn on if this DC-in MOSFET is shorted (current can flow through the shorted MOSFET and through the body diode of the other MOSFET). If the other DC-in MOSFET was shorted it wouldn't turn on (current would be blocked by the other MOSFET in reverse).
              I Had exactly this Case with a Medion P7648 and was wondering why the Battery wasn't charging. I found the issue after replacing the Battery with a new one. Obviously the new one also didn't worked...
              FairRepair on YouTube

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                #8
                Re: Asus GL702VS No charge, unstable GPU power

                Update for anyone interested.

                Replaced both DC-in MOSFETs and now it works just fine. Charges battery and the GPU is once again stable.

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