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lenovo ideapad NM-D031 3VALW issue

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    #1

    lenovo ideapad NM-D031 3VALW issue

    Hi.
    I got dead one.
    3VALW is just pulsing then goes down. i removed the jumper PJ402 and it suddenly stays up but PG pin on that IC is around 0.5v and droping.
    There is no obvious shorts. Wierd thing is that on the other side of the PJ402 i have 1.4V from somwhere ...

    Injecting 3.3v there draws 300mA and nothing is heating up.

    the ic is SY8386BRHC_QFN16 (kinda uncommon here - so i do not have a spare to test it)

    any ideas to check before i order a few of these?
    Tags: None
    #2
    PJ402, consumer side resistance to GND? I feel replacing the chip may not fix it as there seems partial short on consumer side of PJ402.
    Powergood wont rise as long as the jumper is open-so irrevalent finding.
    injecting 3.3V and drwaing 300mA is itself indicative of partial short. Keep it injected for 10-15 mins and pay special attention to KBC chip and PCH if you dont have a thermal camera.
    Btw,how much amps you injected?

    Comment

      #3
      Originally posted by mcplslg123 View Post
      PJ402, consumer side resistance to GND? I feel replacing the chip may not fix it as there seems partial short on consumer side of PJ402.
      Powergood wont rise as long as the jumper is open-so irrevalent finding.
      injecting 3.3V and drwaing 300mA is itself indicative of partial short. Keep it injected for 10-15 mins and pay special attention to KBC chip and PCH if you dont have a thermal camera.
      Btw,how much amps you injected?
      Will check for shorts and give you the resistance tomorrow. As for amps i start from 1A so it didnt even hit it. There is a load switch on this line and removing the jumper right behind it (its not even switching on that 3valw to 3vs so thats not it)
      Will check all points with 3valw and look for something warm.

      Thx for the tip.

      Comment

        #4
        Originally posted by mcplslg123 View Post
        PJ402, consumer side resistance to GND? ...
        Sorry the current draw on consuming side is 0.09A i got confused cause its 0.3W (thets the number i remebered for some reasson.

        34Kohm
        in diode 0.390v drop

        Last edited by reassor; 04-19-2024, 03:21 AM.

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          #5
          The resistance reading is for consumer side with jumper PJ402 open? Right? If so,there is no short on 3V line.

          Comment

            #6
            Originally posted by mcplslg123 View Post
            The resistance reading is for consumer side with jumper PJ402 open? Right? If so,there is no short on 3V line.
            yes same ressistance is on the other side (on the coil) so these look ok.
            I wonder why i do have 1.4v on 3valw line when its disconnected via jumper

            im starting to think iits EC problem.

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