acer a314-41 dead

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  • salawayon
    Badcaps Veteran
    • Nov 2012
    • 568
    • philippines

    #1

    acer a314-41 dead

    board info:
    RAICHU_SR
    18762-1448

    @ PU4301 (SM4378):
    D - 19v
    S - 0v
    G - 0v

    @ BQ24781:
    pin28 - 19v
    4 - 0v

    can't find any short circuit. tried already changing BQ24781 with BQ24780s. i tried to bypass PU4301 and PU4401 and the unit will power up with display.
    anyone could share a schematics for this unit?
  • mon2
    Badcaps Legend
    • Dec 2019
    • 13863
    • Canada

    #2
    Re: acer a314-41 dead

    Post all voltage readings to ground of the charger IC with the adapter connected.

    Comment

    • salawayon
      Badcaps Veteran
      • Nov 2012
      • 568
      • philippines

      #3
      Re: acer a314-41 dead

      @ BQ24781:
      1-0V
      2-0V
      3-0.147V
      4-0v
      5-3.4V
      6-2.85V
      7-0.161V
      8-1.2V
      9-0V
      10-1V
      11-0V
      12-0V
      13-0V
      14-0V
      15-0
      16-0
      17-0.14V
      18-2.4V
      19-0.149
      20-0.149
      21-0.389
      22-0V
      23-0V
      24-6V
      25-5.72V
      26-0154
      27-0.152
      28-19.39V

      Comment

      • mon2
        Badcaps Legend
        • Dec 2019
        • 13863
        • Canada

        #4
        Re: acer a314-41 dead

        Hi. Did you locate the schematics? I have them but it is tied to a paid service so let me share the relevant portions of this schematic.

        The charger IC is a common BQ series from TI. Respectively, TI chargers like to use N-channel mosfets.

        There are 2 x DCin mosfets (as per the sticky article above by @Piernov - a must read).

        Often, faults like yours are linked to the 2nd DCin mosfet = PU4401.

        The ACDRV drive voltage to enable the 2 x DCin mosfets should be ~25 volts if all is normal.

        This value is based on AC ADAPTER voltage + REGN pin voltage = 19v + 6v = 25 volts.

        There is a series resistor of ~4k @ PR4421 that drives the 2 x DCin mosfet's gate pin.

        As a test, you can remove this part but do not lose it. Then power up again.

        Do you now see the ACDRV pin @ ~25 volts ? See attached.

        PS: Very late for you so proceed with caution.
        Attached Files
        Last edited by mon2; 03-12-2023, 09:35 AM.

        Comment

        • salawayon
          Badcaps Veteran
          • Nov 2012
          • 568
          • philippines

          #5
          Re: acer a314-41 dead

          thank you for your inputs. i already solved the problem before i even read your reply. i just replaced PU4301 just by trial and error cause i can't detect any short circuit on PU4301.
          resistance between pins @ PU4301:
          D-S = 2.362Mohms
          D-G = 5.2Mohms
          S-G = 2Mohms
          when applying positive supply at G pin, PU4301 won't function.

          Comment

          • mon2
            Badcaps Legend
            • Dec 2019
            • 13863
            • Canada

            #6
            Re: acer a314-41 dead

            Awesome! Well done.

            Comment

            • mcplslg123
              Badcaps Legend
              • Jun 2015
              • 7262
              • india

              #7
              Re: acer a314-41 dead

              I'll keep my fingers crossed and i beleive it'll return to bench with same problem very soon. A problem cant be solved by replacing a component which is not defective. I doubt, its the heat applied during soldering/de-soldering is at play here.

              Comment

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