Trouble Locating Shorted Component

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  • Alidaco
    New Member
    • May 2018
    • 3
    • USA
    #1

    Trouble Locating Shorted Component

    Hi everyone,

    I've been trying to revive my 2015 Dell XPS 13 (9343). So far I've been able to locate a short to ground on the 1.35v power rail on the system side.

    After doing a bit of research online I came across Louis Rossman's videos on finding short circuits where he applied an expected voltage to the power rail and then feels around the board to see which component gets hot.

    Unfortunately, the board only takes around 0.8 amps at 1.35 volts. Ultimately, 1.35 volts at 0.8 amps isn't enough to make the component hot, and I'm hesitant to crank it up further and apply a voltage higher than what the rail is rated for.

    Any thoughts? I appreciate any help you guys are able to offer!

    -Coleman
    Tags: None
    • R_J
      Badcaps Legend
      • Jun 2012
      • 9514
      • Canada
      #2
      Re: Trouble Locating Shorted Component

      That would tell me that there is NO short to ground at that point. If there was a short the current would be a lot higher. I would not apply a higher voltage. that would not be good.
      Last edited by R_J; 05-16-2018, 08:42 PM.

        Comment

        • Alidaco
          New Member
          • May 2018
          • 3
          • USA
          #3
          Re: Trouble Locating Shorted Component

          Thanks for the reply, RJ. So a resistance of less than 2 ohms would be normal on a power rail that carries low voltage?

          I'd considered the fact that it might not be shorted, but after measuring a bunch of other points on the board, I couldn't find any resistances lower than 50 ohms or so. That's why I thought the 1.4 ohms or so might be a short.
          Last edited by Alidaco; 05-16-2018, 11:32 PM.

            Comment

            • R_J
              Badcaps Legend
              • Jun 2012
              • 9514
              • Canada
              #4
              Re: Trouble Locating Shorted Component

              It does seem low but it might be normal. Do you get any voltage on that line during normal operation? what supplies that 1.35 volts? maybe there is a problem with the source not outputing the 1.35 normally.

              I found this schematic, maybe it is helpfull in some way
              It looks like 1.35volts is used by almost everything
              1.35 seems to be derived from B+ via pl600 coil and PQ600/PQ601 fets and should be able to supply at least 4.48 amps
              Attached Files
              Last edited by R_J; 05-17-2018, 03:07 PM.

                Comment

                • piernov
                  Super Moderator
                  • Jan 2016
                  • 4435
                  • France
                  #5
                  Re: Trouble Locating Shorted Component

                  +1.35V is the RAM voltage. 1.4ohms seem way too low to me for this rail. I've seen only the CPU VCore getting that low and on Pentium 4 only, the others are at least a few ohms in my experience.
                  You should try desoldering PJP600/PJP601 to check which side is shorted, or if PJP600/PJP601 are not labelled/present on the board, remove PL601.
                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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