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820-2390 no green light, not booting after water damage.

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  • 820-2390 no green light, not booting after water damage.

    Hi,

    Got this old board with some whater damage near CPU area. There is no green light. Fans spin with SMC BYPASS but no image no sound not booting.


    Getting this values on main rails:


    PPBUS_G3H 8.41V

    PPBUS_CPU_IMVP_ISNS 8.41V

    PPDCIN_G3H 17.04V

    PP3V42_G3H 3.42V

    PP3V3_S5 3.3V



    The only thing i noticed it that on U7000 the resistance between 27/28 is 21.9 and 17/18 is 21.5 too. I know for ISL 6529 second value mst be about 3ohm but seems that this one (ISL6258...) is 21 both. ANyway changed it and same things happening.


    Any suggestion?

  • #2
    Do you get correct voltage at C7771?
    Don't forget to check it, before sending the machine out to the client.

    Check current and voltage sensing circuits from page 45.
    U7000, pins 17/18 have correct 20 ohms, as per schematic.
    Inspect for corroded traces/resistors under microscope around affected areas.

    When in SMC bypass, do you get voltage at all big coils?

    Comment


    • #3
      getting 1.1V pm C7771. This was first i checked.


      There is no visible corrosion except of C7115 and a couple of near components. Anyway will try to clean one more time in ultrasonic and back once finish. THanks.

      Comment


      • #4
        Ultrasonic bath can clean corrosion, but will not rebuild broken traces.
        You have a problem with some I/V sensor; like PBUS_VSENSE, or other from mentioned page.

        Comment


        • #5
          When smcbypass i am getting.

          L7100/01 0.9V


          CPU and both GPU are heating.


          I have checked whole board and cannot find anything.


          Also from page 45


          PBUSVSENS_EN 0V is that normal?


          Q5315

          4 - 8.40
          5 - 8.30
          6 - 8.25

          3 and 2 0V



          About PPBUS 8.4 is that normal? Does it likes 820-00165 that mean smc issue?




          And CPU Vcore side sensor:

          U5388 (seems be ok)

          Pins 4-5-6 8.4V
          Pin 3 3.4V




          P.S: IMVP6_IMON must be 0?
          Last edited by BCN_Techs; 2 weeks ago.

          Comment


          • #6
            Also i am checking 1 wire and on R6912 getting 6V on pin 1 and 0 on pin 2. Resistance is ok 330KOhms,

            Comment


            • #7
              You cannot have more than 3.3V at U5388 output, unless it is bad!
              Its output is related with voltage drop across R5388.
              For example, 5A will generate 2.5V at C5335.
              When board is off, you should have 0V there...

              Comment


              • #8
                sorry, it's 0V all other measerements are ok.

                About ppbus 8.4 and one - wire circuit any wrong thing?


                also why i am getting this: "Also i am checking 1 wire and on R6912 getting 6V on pin 1 and 0 on pin 2. Resistance is ok 330KOhms,"


                Thank you

                Comment


                • #9
                  Nothing wrong with R6912, it has correct voltages.
                  Usually U6915 is the "bad guy" there; but Q6910 fails too.
                  Post their voltages...

                  Comment


                  • #10
                    Finally i replaced U6915, Q6915,Q6910, U7000 (again) and many other and now computer starts. The only problem still remains is that its not charging. No green light. It detects magsafe because battery in status bar change status but not charging.


                    Seems one wire issue but i cant find nothing more to replace.

                    Comment


                    • #11
                      U6915 was the problem. seems donor u6915 was bad too.

                      THank you very much

                      Comment


                      • #12
                        You don't need to change so many components.
                        Just read their voltages and interpret the values...

                        Comment

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