Surfave Pro 5 no power +vsys 0.4V

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  • Harryrepair
    Senior Member
    • Jul 2016
    • 82
    • Germany
    #1

    Surfave Pro 5 no power +vsys 0.4V

    Hello all,

    i am trying to fix a surface pro 5, M1013936-015

    As you can see +vsys is at 0.4V which appears to me much too low.
    Ext_Dc_in is always 0V when charger is plugged but PWR_SL1_F is stable at 15V.

    3V3_SAM is at only 0.428V, should be 3.3V , isn`t it?

    Appreciate all help
    Attached Files
    Last edited by Harryrepair; 01-06-2022, 10:32 AM.
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 14250
      • Canada
      #2
      Re: Surfave Pro 5 no power +vsys 0.4V

      To debug the voltage rails that are deemed to be low, remove all power to the logic board.

      Meter in resistance mode (2k scale) - measure & post the resistance to ground for the low voltage rails.

      If the resistance is very low (as we know, 'resistance is futile') then you may have a bad cap on that rail.

        Comment

        • Harryrepair
          Senior Member
          • Jul 2016
          • 82
          • Germany
          #3
          Re: Surfave Pro 5 no power +vsys 0.4V

          here are my results.
          6.175k appears low to me for a main power rail, am i wrong?
          Attached Files

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14250
              • Canada
              #4
              Re: Surfave Pro 5 no power +vsys 0.4V

              Are schematics and boardview files posted for this product here in the forum ?

              Have the attached in my database but the logic board # is different.

              The resistance looks fine and is not too low.
              Attached Files

                Comment

                • Harryrepair
                  Senior Member
                  • Jul 2016
                  • 82
                  • Germany
                  #5
                  Re: Surfave Pro 5 no power +vsys 0.4V

                  I use xzz for this device and did not compare the board numbers as every part in the boardview is in its place on the board.

                  What can drop voltage without being short?

                    Comment

                    • mon2
                      Badcaps Legend
                      • Dec 2019
                      • 14250
                      • Canada
                      #6
                      Re: Surfave Pro 5 no power +vsys 0.4V

                      There could be a shorted cap downstream that is causing an excessive load -> leading to the massive voltage drop.

                      Remove all power.

                      Meter in resistance mode (try 2k ohms).

                      Measure & post the resistance to ground for that rail that is low in voltage.

                      Red meter probe on the rail & black meter probe to ground. Post the measurements. If the meter shows OL or '1' then the resistance may be too high for the selected meter scale. This is a good sign. Just select the higher setting to proceed.

                        Comment

                        • Harryrepair
                          Senior Member
                          • Jul 2016
                          • 82
                          • Germany
                          #7
                          Re: Surfave Pro 5 no power +vsys 0.4V

                          I spent some time with this board and did not find any short, but what i see on the earlier posted sheet, is PWR_SL1_F is powering EXT_DC_IN.

                          EXT_DC_IN is produced by Q6308. Nothing appears short, EXT_DC_IN stays 0V
                          Find attached my readings.

                          What i furthermore found on the board is U7004 having a hole.
                          I need to order this part.
                          Attached Files

                            Comment

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