A1990 820-01814 5v 0.2-0.3a

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  • rtimots
    Member
    • Dec 2022
    • 11
    • Latvia
    #1

    A1990 820-01814 5v 0.2-0.3a

    Hello, got this a1990 for repair.
    Initialy thought some cd3215 is dead but no, i dont have cycleing on any ports and on all of the the readings are the same. I have all LDO voltages exept BMC. PPDCIN_G3H is ok. HvGate1 is 7.6v and gate2 is 11v. PP20V_USBC_XB_VBUS Is 5v. PP3V3_G3H is 0v , CHGR_VDDA is 5v , TP_CHGR_EN_VR1 is 5v.
    I'm ir right that maybe U7000 is dead? kinda lost and dont know where to look next, maybe some one has an advice?
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 14631
      • Canada
      #2
      Re: A1990 820-01814 5v 0.2-0.3a

      What is the voltage to ground of PPBUS_G3H @ F7000 or F7001 ?

      Check both sides of these fuses.

        Comment

        • rtimots
          Member
          • Dec 2022
          • 11
          • Latvia
          #3
          Re: A1990 820-01814 5v 0.2-0.3a

          PPBUS_G3H @ F7000 or F7001 Is 0v at bouth sides. Tested if the the fuse is good, and it is but i think i have a dead on short here because at resistance mode i have 5 ohm’s and at diode mode .04v

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14631
              • Canada
              #4
              Re: A1990 820-01814 5v 0.2-0.3a

              Indeed. With low air pressure + flux, carefully remove F7000 and F7001 off the board.

              Then check the resistance to ground from the producer side (aka ISL9240 side) and the consumer side (downstream of the fuses).

              Post each measurement.

                Comment

                • rtimots
                  Member
                  • Dec 2022
                  • 11
                  • Latvia
                  #5
                  Re: A1990 820-01814 5v 0.2-0.3a

                  So today I removed the F7000 and F7001, at PPVBAT_G3H_CHGR_REG side I have 0.8kOhm and at PPBUS_G3H side I have 4.7ohm.
                  If I understand correctly at this point I should inject voltage into it and see what becomes hot?

                    Comment

                    • mon2
                      Badcaps Legend
                      • Dec 2019
                      • 14631
                      • Canada
                      #6
                      Re: A1990 820-01814 5v 0.2-0.3a

                      Correct. Keep the injection voltage @ 1 volt or less. Current as high as available on your DC power supply. No other power source.

                      Most likely you will find a shorted tantalum capacitor on the board that will crack under this pressure. Remove that capacitor and test again for the resistance to ground. If the resistance returns to a high level, solder back the fuses and check again.

                      Before soldering the fuses, confirm that the voltage from the ISL regulator is in the normal range for PPBUS_G3H = ~12 volts.

                      Respectively, the shorted cap is causing a high current draw and the ISL knows this via the current sense resistor so it is powering down this critical power rail.

                        Comment

                        • reformatt
                          Badcaps Legend
                          • Feb 2020
                          • 1458
                          • Australia
                          #7
                          Re: A1990 820-01814 5v 0.2-0.3a

                          https://www.youtube.com/watch?v=Tavtryit3Uc

                          Common issue on this model, check Paul’s clip first.

                            Comment

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