Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

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  • classicandy
    Badcaps Veteran
    • Apr 2018
    • 308
    • Nigeria

    #1

    Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

    Hi, I have a Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) that is not powering On.

    Immediately i plug the charger, the 3.3v/5v I.C gets extremely hot. I don't have the schematic yet.
  • piernov
    Super Moderator
    • Jan 2016
    • 4435
    • France

    #2
    Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

    Check for short to ground on outputs of 3V/5V regulator. (LDOs and buck converters)
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment

    • classicandy
      Badcaps Veteran
      • Apr 2018
      • 308
      • Nigeria

      #3
      Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

      Before that I.C started getting hot, there was a buzzing sound coming from a component close to the DCIN Jack. Check the photo attached. I think the charger was faulty too which caused it to make that sound.

      I have replaced the charging I.C (BQ715), it still made that noise until the noise stopped and the 3.3v/5v I.C started getting HOT. I've changed the Charger and also the 3.3v/5v I.C, it still gets hot.
      Attached Files

      Comment

      • classicandy
        Badcaps Veteran
        • Apr 2018
        • 308
        • Nigeria

        #4
        Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

        Originally posted by piernov
        Check for short to ground on outputs of 3V/5V regulator. (LDOs and buck converters)
        Ok.

        The previous 3.3v/5v I.C was TPS51285B and i replaced it with TPS51225. Both still gets hot.

        From the datasheets, they are very similar. Should i be worried or its still compatible?

        Thanks for the quick reply

        Comment

        • piernov
          Super Moderator
          • Jan 2016
          • 4435
          • France

          #5
          Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

          TPS51285B and TPS51225 are not directly compatible (VREG5 is off by default for TPS51225 and on by default for TPS51285B, switching frequencies are different so it may require different values for output filters). That's not the problem here though.
          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

          Comment

          • classicandy
            Badcaps Veteran
            • Apr 2018
            • 308
            • Nigeria

            #6
            Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

            Originally posted by piernov
            Check for short to ground on outputs of 3V/5V regulator. (LDOs and buck converters)
            No short to ground on VREG3 (pin 3) and VREG5 (pin 13).
            186k ohms on both outputs.

            VCLK (PIN 19) = 78K ohms
            SW1 (PIN 18) = 114K
            SW2 (PIN 8) = 126K
            PGOOD (PIN 7) = 14.4K
            DRVL2 (PIN 11) = 95K
            DRVL1 (PIN 15) = 96K
            DRVH2 (PIN 10) = 125K
            DRVH1 (PIN 16) = 118K
            CS2 (PIN 5) = 11.3K
            CS1 (PIN 1) = 11.3K


            Also, i've removed inductors for 3.3v and 5v outputs, so no connection on that rail to the rest of the board.

            Comment

            • classicandy
              Badcaps Veteran
              • Apr 2018
              • 308
              • Nigeria

              #7
              Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

              Originally posted by piernov
              TPS51285B and TPS51225 are not directly compatible (VREG5 is off by default for TPS51225 and on by default for TPS51285B, switching frequencies are different so it may require different values for output filters). That's not the problem here though.
              Ok, I can change it back. Seems the previous one (TPS51285B) might still be good.

              Comment

              • piernov
                Super Moderator
                • Jan 2016
                • 4435
                • France

                #8
                Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

                Weird, check if the MOSFETs for the buck converters are shorted drain/source/gate. (it may be normal to have low resistance between gate and source with the regulator soldered to the board, but it should not be 0 ohm)
                OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                Comment

                • classicandy
                  Badcaps Veteran
                  • Apr 2018
                  • 308
                  • Nigeria

                  #9
                  Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

                  Originally posted by piernov
                  Weird, check if the MOSFETs for the buck converters are shorted drain/source/gate. (it may be normal to have low resistance between gate and source with the regulator soldered to the board, but it should not be 0 ohm)
                  ok.

                  no shorts on the MOSFETs

                  Comment

                  • mcplslg123
                    Badcaps Legend
                    • Jun 2015
                    • 7262
                    • india

                    #10
                    Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

                    check kbc for shorting.

                    Comment

                    • classicandy
                      Badcaps Veteran
                      • Apr 2018
                      • 308
                      • Nigeria

                      #11
                      Re: Lenovo ThinkPad 11e (DALI6JMB8E1 REV:E) not powering On

                      Originally posted by mcplslg123
                      check kbc for shorting.
                      Thanks for the suggestion, I found KBC to be shortened. After removing KBC, short was gone. Sorry for not replying on time.

                      Comment

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