Lenovo Thinkpad L480 : 3VALW rail shorted to ground, but I can't find the shorted component

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  • mkdj
    Member
    • Mar 2025
    • 21
    • France

    #1

    Lenovo Thinkpad L480 : 3VALW rail shorted to ground, but I can't find the shorted component

    Dear all,

    Laptop is Lenovo Thinkpad L480 (boardview can be found in this badcaps topic). When pressing the power button the LED power light turns on, but nothing else happens.

    I removed the motherboard, checked for shorts on the main inductors. I found that there is a short to ground on the +3VALW_P rail (@PL201). I soldered a wire on the PL201 inductor, and I injected up to 1.3V with my power supply. Current drawn is approximately 3.2A.

    I used a small thermal camera to locate the shorted component. But nothing on the board heats significantly, except the CPU.

    This is my first short circuit detection on a motherboard. Any advice on what I should do now?

    Regards,
    mkdj
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14263
    • Canada

    #2
    nothing on the board heats significantly, except the CPU.
    Most likely the defect is with the PCH (CPU) that uses the same rail.

    Comment

    • mkdj
      Member
      • Mar 2025
      • 21
      • France

      #3
      Thank you mon2 for your comment.

      Does that mean that the CPU is dead, and the board can't be fixed without replacing the CPU?

      What if I reflow or (try to) reball the CPU, could that solve the issue?

      Regards,
      mkdj

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