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Thinkpad L480 , Short To Ground, CPU gets Hot

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    Thinkpad L480 , Short To Ground, CPU gets Hot

    Hi,

    i would like to hear your thoughts.
    This is my first attempt to repair a broken ThinkPad.

    I got a Thinkpad L480 with no power or any sign of life.
    I checked Memory Module, WiFi Module and Display, all are fine.

    I have Schematics and Board View.

    The L480 has no LED and the fan is not spinning or moving with the USB-C PSU (65W).

    I measured all Coils and all i have is

    +5VALW with 5V
    +3VALW with 0V

    I opened PJ202 and i get +3V at +3VALW.

    So i checked for any shorted CAP (didn´t find any).

    I injected 1V / 5A at PJ202 but nothing got hot.
    I used Ice Spray over the whole Board, nothing gets hot.

    After removing the Heatsink, the only thing that was hot was the i5-8530U smaller Die.

    If i thouch the Die with my Lips, i get a tiny electric Shock ...

    So i assume, the CPU i shorted.

    Is there anything else i can try or is this Board now a donor Board for Parts?

    Thanks

    Jürgen

    #2
    Re: Thinkpad L480 , Short To Ground, CPU gets Hot

    Obviously PCH is shorted as always.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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      #3
      Re: Thinkpad L480 , Short To Ground, CPU gets Hot

      I have an hp 250 g5 with a similar 3v short issue. The PCH die next to the cpu gets warm, when I cleaned the grease off, using my magnifying glass I could see a small gritty looking crator in the mirror finish of the chip.
      There are capacitors underneath the chip on the other side of the board, and undeterred removed every shorted cap i could find, but the caps i removed all tested good.
      Freezer spray would of been a quicker diagnostic tool, every days a school day.

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        #4
        Re: Thinkpad L480 , Short To Ground, CPU gets Hot

        No point removing those tiny capacitor on back of SOC unless and otherwise its liquid spilled/RTC shorted issue.

        Comment


          #5
          Re: Thinkpad L480 , Short To Ground, CPU gets Hot

          Although initially expensive, a thermal camera will save you countless hours of time. Can't put a price on that.

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