A2279 - 820-02841 cycling

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  • iMuhtaseb
    Senior Member
    • Jan 2017
    • 125
    • Palesine
    #1

    A2279 - 820-02841 cycling

    A2279 (14" M2 Pro | 820-02841)
    No power - switches to 20V for a swift moment then starts cycling/switching on all USB-C ports.

    Board is clean.. I looked over it three times and found little corroded caps for a display data lines.. replaced them and they have nothing to do with the issue.

    Customer is using a branded USB-C to MagSafe cable. I looked for shorts (diode mode) nearly all lines, PPBUS, 3v8_AON, 5V_S2, 1v2_S2, 1v2_AWAKE, 1v8_AON.. and coils around master PMIC and slave PMIC; all reads normal.
    I suspected that ISL might be bad, took an educated guess and replaced it; same issue.
    Diode readings around all CDs read OK..
    On thermal camera I see a small warmth pulse from the CD, U9400, U9500 and the M2 SoC itself while cycling..
    I feel like it's a small corroded somewhere but I cannot seem to find it.. any tips?
    Tags: None
    • Answer selected by iMuhtaseb at 09-23-2025, 08:57 AM.
      iMuhtaseb
      Senior Member
      • Jan 2017
      • 125
      • Palesine
      It refused to enter DFU because it was cycling.. I forced DFU on board and revived the device and now it's on.. how? and why? God knows but now it need thorough testing.. thank you so much mon2 will keep you posted
        • Selected Answer

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        • mon2
          Badcaps Legend
          • Dec 2019
          • 14607
          • Canada
          #2
          What is the voltage to ground @ F5200?

          Remove all power. Measure the resistance across C5220 = checking the input current full path resistance.

            Comment

            • iMuhtaseb
              Senior Member
              • Jan 2017
              • 125
              • Palesine
              #3
              F5200 every 5 seconds goes between 6v to 12.29 cycling.

              C5220​ (measuring resistance with each lead on each side of cap) = 3.8 ohms

                Comment

                • mon2
                  Badcaps Legend
                  • Dec 2019
                  • 14607
                  • Canada
                  #4
                  Try a DFU

                  https://www.youtube.com/watch?v=q-FsB2onSx0

                    Comment

                    • iMuhtaseb
                      Senior Member
                      • Jan 2017
                      • 125
                      • Palesine
                      #5
                      It refused to enter DFU because it was cycling.. I forced DFU on board and revived the device and now it's on.. how? and why? God knows but now it need thorough testing.. thank you so much mon2 will keep you posted
                        • Selected Answer

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