MSI GT70 2PE Voltage dropping on the main power rail

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  • HERETIK10
    Member
    • Dec 2020
    • 15
    • France
    #1

    MSI GT70 2PE Voltage dropping on the main power rail

    Hi everyone,
    I have a strange problem (for me) on an MSI GT70 2PE laptop.
    When it's under heavy load, power goes steadily to the battery (for 2 or 3 seconds) then return to the charger. If I remove the battery it turns off.
    The higher the load, the lower the voltage on the main rail. We go from 19.5V, PC connected to the charger but turned off (normal consumption of 0.06A)
    On, when it draws 2A the voltage is 19.2V, then eventually collapses to 18.5V (and turns off) around 5A.
    I removed the first 2 mosfets (PQ13 & 14) from the main rail, without noticeable change.
    Anyone have a lead?
    Thank you in advance for your help.

    Schematic : https://www.badcaps.net/forum/troubl...631-schematics
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 13829
      • Canada
      #2
      Is the power adapter properly rated for this laptop use?

        Comment

        • HERETIK10
          Member
          • Dec 2020
          • 15
          • France
          #3
          Thank you for your answer. Yes no problem at this level, I had the problem with my original charger and my 60V 12A lab power supply.

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 13829
              • Canada
              #4
              Review the voltage to ground on PU11 (charger IC). There should be a resistor based voltage divider that will accept the main DCin adapter voltage and lower it to a safe value that is being monitored by this charger IC. If the threshold of the lower voltage is within range - the ACOK signal should be true. If the voltage drops below this threshold, the ac adapter is not suitable. Review the conditions when the voltage of the main power rail drops. Suspecting that the threshold of 2v7 (typical) is no longer valid. Review the charger IC datasheet on how the ACDET pin functions.

                Comment

                • HERETIK10
                  Member
                  • Dec 2020
                  • 15
                  • France
                  #5
                  Thanks for your response, but I don't think it's a charger problem. Indeed, once the voltage drops too low, the PC goes on battery, it looks like I have something shorted on the main rail which creates resistance. But I don't see what it could be... I soldered a wire directly to the output of PQ14 from my lab power supply and the problem remains the same. The voltage drop begins at low consumption (1A) and intensifies as a load is applied.

                    Comment

                    • HERETIK10
                      Member
                      • Dec 2020
                      • 15
                      • France
                      #6
                      Is it possible that a failing CPU mosfet could create this type of problem?

                        Comment

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