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820-3476 Green/Orange light, Not turning on, Corrosion around U7501

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  • 820-3476 Green/Orange light, Not turning on, Corrosion around U7501

    Hey everyone,

    I have a slightly liquid damaged board which initially had no light but there was corrosion around U7501 so I replaced the the chip and also changed capacitors C7500 (one pad was completely destroyed so made a jumper going to Pin 23 of U7501) and C7503. No I have a green which now turns to orange light but still not powering on and nothing warms up either.
    PPBUS_G3H 12.56V
    PPDCIN_G3H 16.41V
    PP3V42_G3H 3.42V
    PPVRTC_G3J 3.42V
    PP5V_S5 1.7001V
    PP5V_S4 0V
    PP5V_S0 0V
    PP3V3_S0 0V
    PP3V3_S3 0V
    PP3V3_S5 3.29V

    I'm basically getting no 5V (besides 1.7 on S5) and no 3V3 RailsThese are some of my readings and I have checked all the rails but nothing else looks damaged and not sure where to go from here.

    Many thanks for any help.
    Last edited by SamMac; 09-08-2018, 10:29 AM.

  • #2
    Is trackpad disconnected?
    Check C7505 and C4807 too.


    • #3
      Double check if pin 23 is actually making contact with the chip as it usually is destroyed.

      SMC_PM_G2_EN present?


      • #4
        Everything but fan and dc board connected.
        Both capacitors giving the same voltages (1.7V) and looks fine.

        Won't be able to check Pin 23 since I am doing this at home and microscope is at the workshop. But it seems good as there is continuity.

        SMC_PM_G2_EN is present with 3.4V


        • #5
          "Both capacitors giving the same voltages (1.7V) and looks fine"
          Already knew that...
          I asked to remove them and see if voltage rise.
          Don't you imagine better method to check components than the eye???


          • #6
            I would first confirm pin 23 actually has 12.6V on it before doing anything else.


            • #7
              Quadruple checked Pin 23 and its only giving 0.6V and changes everytime i make an adjustment to the jumper (goes up to 1.5V)

              Removing either capacitors does nothing to the voltages
              Last edited by SamMac; 09-10-2018, 04:12 PM.


              • #8
                Rebuild its trace...


                • #9
                  Trace is simply corroded somewhere.....


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