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Lenovo NM-B861 (Carbon X1 7th Gen) No power no charge light & exploded cap

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    Lenovo NM-B861 (Carbon X1 7th Gen) No power no charge light & exploded cap

    Hello all! I am new to all this so please bare with me.

    I have a lenovo carbon x1 7th gen a friend gave me. It hung and he turned it off to restart. After shutting down it had no power/no charge light. I pulled it apart and found a blown cap on what appears to be the main power rail. I cleaned up the area and tested, but no luck. Everything around the coils/inductors comes up shorted (caps, ic pins etc) to ground. I also have a few caps here and there that seem to be shorted to ground. I removed an IC and a cap to see if the short would go away but no luck. (i removed the ic because freeze spray showed it was getting hot and I thought this might be the cause.)

    Does anyone have a boardview for this? I can't seem to come up with one anywhere. I believe this particular model was a Costco only unit.

    Physical inspection of the board looks good otherwise. As stated I am new to all this and not sure what to check next. I'd really like to fix this laptop as I need one and funds are tight right now as I was laid off for CV19 related reasons.

    Let me know if any clarification is needed. As stated I am totally new to this level of diagnostics so you may have to dumb it down for me. I am however very eager to learn more.
    Attached Files

    #2
    Re: Lenovo NM-B861 (Carbon X1 7th Gen) No power no charge light & exploded cap

    The short-circuited capacitor may cause MOSFET failure at the AC_IN input. Check the 20V line from the DC jack input. Are there any other short circuits in the Sys + B line? some coils may show low omage. Like 6 ohms 20 ohms.
    I'm not happy to be so strong. because it's not humanly

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      #3
      Re: Lenovo NM-B861 (Carbon X1 7th Gen) No power no charge light & exploded cap

      Originally posted by Sametbey View Post
      The short-circuited capacitor may cause MOSFET failure at the AC_IN input. Check the 20V line from the DC jack input. Are there any other short circuits in the Sys + B line? some coils may show low omage. Like 6 ohms 20 ohms.
      No exactly sure what the sys + b line is exactly. I did measure most of the coils on the top of the board and they were giving me like 5-8ohms if I read correctly. I sadly don't have a working laptop board around so I can measure it and compare coil readings.

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        #4
        Re: Lenovo NM-B861 (Carbon X1 7th Gen) No power no charge light & exploded cap

        in picture
        Attached Files
        I'm not happy to be so strong. because it's not humanly

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          #5
          Re: Lenovo NM-B861 (Carbon X1 7th Gen) No power no charge light & exploded cap

          Originally posted by Sametbey View Post
          in picture
          Thank you!

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