3437 Low Res to Gnd on 3v42

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  • BrickBreaker
    Senior Member
    • Jan 2018
    • 52
    • United States
    #1

    3437 Low Res to Gnd on 3v42

    I have a 3437 air board, ppbus was only 0.8V, 3v42 - 1.3V
    PPDCIN 3v42 - 15.55V
    Resistance to ground on 3v42 was 30 ohms
    KG board measured 22 kohm

    Started removing stuff and now I'm out of stuff to remove.
    I ended up removing ISL, SMC, U1900, U1950, debug, IO conn, tpad conn, U5110
    Checking resistance to ground after each component. 60 ohms now.

    I'm thinking it must be leaky to ground in the CPU or internal trace.
    Tags: None
    • piernov
      Super Moderator
      • Jan 2016
      • 4435
      • France
      #2
      Re: 3437 Low Res to Gnd on 3v42

      Liquid damage?
      Removed U7090 or L7095? U4650? There's also U3740 and then all the capacitors left.
      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

        Comment

        • BrickBreaker
          Senior Member
          • Jan 2018
          • 52
          • United States
          #3
          Re: 3437 Low Res to Gnd on 3v42

          Yes to U7090, forgot to list that one. I haven't removed L7095 but I removed C7099 and C7098. Now the only path to ground is through the feedback voltage divider which I checked earlier (haven't removed yet) but curiously both Ra and Rb measured 127 kohm??? Thanks for the suggestions, back to the chopping block.

            Comment

            • BrickBreaker
              Senior Member
              • Jan 2018
              • 52
              • United States
              #4
              Re: 3437 Low Res to Gnd on 3v42

              No change after removing U4650, U3740, and R7096.

                Comment

                • BrickBreaker
                  Senior Member
                  • Jan 2018
                  • 52
                  • United States
                  #5
                  Re: 3437 Low Res to Gnd on 3v42

                  F me I knew when I found it it would be visibly damaged. I am the worst at using my eyes. Got to C5002 and yea it was burnt. Only a little but obvious to one of us. Thanks for the help, solved. Now to put everything back eeeee

                    Comment

                    • piernov
                      Super Moderator
                      • Jan 2016
                      • 4435
                      • France
                      #6
                      Re: 3437 Low Res to Gnd on 3v42

                      Well at least you found it, good job, hoping it's the only issue with the board.
                      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                        Comment

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