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Lenovo 17IIl05 NM-D031 Shorted 1.8 rail

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    #1

    Lenovo 17IIl05 NM-D031 Shorted 1.8 rail

    Resistance at all the coils seem fine except for the 1.8V coil (PL9800) which reads 0 ohm.
    The 3.3V coil has also a very low resistance of 11 ohm, after trying to disconnect some components and isolate the problem it appears that the problem comes from +3VALW_PCH (unsoldered the PJ4602 bridge).

    I have little hope but I am a beginner so I would like your advice before considering the motherboard dead.

    Link to schematic - https://www.badcaps.net/forum/troubl...31-motherboard

    Thanks
    Last edited by SMDFlea; 11-18-2024, 11:23 AM. Reason: Link to schematic
    Tags: None
    #2
    To clarify, remove all power. Meter in resistance mode. Measure the resistance to ground for each coil. Do not measure the resistance across the coil itself which is nothing more than a long piece of wire so it will report a low resistance.

    Can you confirm this is how you are measuring the resistance for a short?

    Comment

      #3
      Originally posted by mon2 View Post
      To clarify, remove all power. Meter in resistance mode. Measure the resistance to ground for each coil. Do not measure the resistance across the coil itself which is nothing more than a long piece of wire so it will report a low resistance.

      Can you confirm this is how you are measuring the resistance for a short?
      Yes this is how I measure them.

      Comment

        #4
        1.8V coil (PL9800) which reads 0 ohm.
        This is a dead short. Flux and lift up one leg of PL9800. Then test again. Which side of this leg of the voltage rail is shorted? Is it the inductor side (producer) or the downstream (consumer) side?

        PS: You may be able to test the same by removing the solder blob @ PJ9803 (if present). Essentially we are attempting to isolate the producer and consumer sides of this shorted power rail.
        Last edited by mon2; 11-18-2024, 10:26 AM.

        Comment

          #5
          Originally posted by mon2 View Post

          This is a dead short. Flux and lift up one leg of PL9800. Then test again. Which side of this leg of the voltage rail is shorted? Is it the inductor side (producer) or the downstream (consumer) side?
          The downstream side I guess (the side on the right, toward the ddr slot)

          Comment

            #6
            Would you have an adjustable power supply? If yes, dial it up to 1 volt (to be safe) and inject onto the side showing this short. Then monitor who heats up from this injection. Hoping it is a local capacitor onboard.

            Comment

              #7
              Originally posted by mon2 View Post
              Would you have an adjustable power supply? If yes, dial it up to 1 volt (to be safe) and inject onto the side showing this short. Then monitor who heats up from this injection. Hoping it is a local capacitor onboard.
              Only thing heating up is the PCH, not even hot but still...
              It's over?

              Comment

                #8
                Dont waste your tome bro on this unit. A short to ground on 1.8V coupled with 3.3V rail is absolute guarantee of shorted SOC.

                Comment

                  #9
                  Originally posted by mcplslg123 View Post
                  Dont waste your tome bro on this unit. A short to ground on 1.8V coupled with 3.3V rail is absolute guarantee of shorted SOC.
                  I thought so, to the graveyard it goes.

                  Thanks.

                  Comment

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