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Lenovo Yoga NM-A381 Motherboard no power, wont turn

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    #1

    Lenovo Yoga NM-A381 Motherboard no power, wont turn

    Hi All,

    Looking for advice on where to start and diagnose the problem to resurrect my laptop.

    I am only getting 5V on Pin 1 (PJP1) when the power is plugged in. It should be 20V.
    Laptop uses funny USB charging port. When plugged in to laptop should recognise and then USB supply 20V, otherwise default is 5V.

    I can order a new power socket or could, but how can I rule out other issues on the motherboard first?

    I have read other forums on here that is similar issue but they are a bit ahead of me in diagnosis.

    Any advice or assistance would be appreciated.


    Attached schematic and board view.
    Attached Files
    Last edited by BumThief; 06-20-2021, 12:53 AM. Reason: Add photo
    Tags: None
    #2
    Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

    Check your Charging Port visually and also the Port of the Adapter. I have in Mind it is a square one, yellow colour with a small Triangle (for Not accidentally Plug in another USB-Port).

    Share Pic how it Looks inside

    They're Well known for being physically damaged.
    FairRepair on YouTube

    Comment

      #3
      Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

      Probably +3VL are missing due to the kbc (IT8386E-192) being in shot-circuit.

      As Sephir0th mention, the usb port from charger is probably damaged, and trough USB_ID injects 20v. to the IT8386E.

      It is a common issue in NM-A381 motherboard.

      Comment

        #4
        Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

        Hi All,

        Thank you for getting back to me, sorry for delayed reply, tried to get a better camera to take photos but they still look bad.
        Attached photos of cable and socket. I can try get better quality if need be.

        The sockets don't look too bad, there are marks from general use it seems. Nothing out of place and pins don't look damaged.

        If IT8386E-192 is short circuited, would I have to install identical one (IT8386E-1502-192)?
        Or can I use any IT8386E-XXXX-192?

        Kind regards
        Attached Files

        Comment

          #5
          Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

          I have bought and testing a new power cord and am now getting 20V as expected.

          Laptop still wont turn on and no charging light on battery.

          Should I replace IC chip?

          I noticed PL202 getting hot, however I couldn't measure a voltage coming through. This doesn't seem right?
          Last edited by BumThief; 06-30-2021, 05:48 PM.

          Comment

            #6
            Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

            1) PL202 is a coil and under normal conditions, it will be warm / hot to the touch.

            2) If PL202 is not showing any voltage then there is a fault on that rail.

            What is the voltage reading of +5VALW ?

            3) Power down and set your meter to resistance mode (lowest scale).

            What is the readings in ohms with:

            red lead on PL202, pin # 2 with black meter lead on ground ?

            If the resistance (of +5VALW) is very low then you have a short condition on that rail that needs to be investigated. Could be a bad (shorted) cap or another condition.

            4) What are the voltage readings

            @ ACDET ?

            @ ADIN_1 ?

            @ V_CHG ?

            @ V_PATH ?

            Comment

              #7
              Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

              Hello Mon2,

              Thank you for your response.

              I fear something may have happened while testing, when I plug in charger, fans will turn on and IC gets hot very quickly. I measured and then had to step away, came back and plugged in charger and this is the case.

              I managed to get a few measurements before this happened

              There is was no 5VALW present.

              PL202 = 403 ohms
              Now when i measure it is shorted.

              ACDET = 2.6V
              ADIN_1 = 20V

              I am hesitant to try measure V_CHG and V_PATH due to issues mentioned above.
              Last edited by BumThief; 07-02-2021, 12:19 AM.

              Comment

                #8
                Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

                Which ic gets hot quickly?

                Comment

                  #9
                  Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

                  You must be careful while measuring. Since the legs are small in materials such as a charge chip, you should use a needle-tipped probe. Measure which side the short-circuit is on by lifting the PL202 coil. After the coil, you can detect the heated part by giving a voltage starting from 1v (max 3.3V).

                  ACDET and ACOK outputs of the charging chip are important. Required for the IO chip to start.
                  Last edited by Sametbey; 07-02-2021, 01:58 AM.
                  I'm not happy to be so strong. because it's not humanly

                  Comment

                    #10
                    Re: Lenovo Yoga NM-A381 Motherboard no power, wont turn

                    UE1 i think it is, the IT8386E-192 CXS chip

                    Comment

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