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820-2327 water damage, ppbus_g3h low at 8.15V

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  • 820-2327 water damage, ppbus_g3h low at 8.15V

    Hello guys,

    ancient board, I know, but still practicing.

    Board was clean except some mild corrosion on U7000. Replaced the chip and now I get 8.15V at pin 1 of L7000. When I plug in a good battery I get 12V on pin 1 of L7000. I short the SMC_ONOFF pads, no fan spin.

    What next?

  • #2
    Resistance between pins 17/18 and 27/28? Resistance to GND on 3V42 rail?

    Comment


    • #3
      Am I supposed to measure resistance between these pins with the MagSafe disconnected? That's what I did and resistance between pins 17/18 is 21.2 Ohm, 27/28 is 20.5 Ohm. Resistance to GND on 3v42 rail is 0.324.

      Comment


      • #4
        All without power of course. Resistance to GND on 3V42 is 0.342 what? Is that diode mode? I need resistance.
        You did replace U7000 with ISL6258 and not 6259?
        Green light ok?

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        • #5
          You are right, I measured in diode mode. Resistance to GND on 3V42 is 22.84 kOhms. Taking a closer look I saw that there has been worked on this board before. U2801 was missing and I put it back in place. Now I get a fan spin for about 10 seconds, short pause for 2 seconds and then spins infinitely. Is this board dead?

          Comment


          • #6
            On/Off and On again is the worst you can have. The only easy fix would be if CPU Vcore is not coming on. If there is Vcore on L7400 then this board is trash.

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            • #7
              I get 0.989V on pin2 of L7400 Oh, well. At least we tried. Thank you Duke.

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              • #8
                Usually this is a dead MCP. Only other thing is to inspect for corrosion or missing/damaged parts/traces.

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                • #9
                  Somewhere in particular, or corrosion could be just about anywhere? Thanks anyway.

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                  • #10
                    CPU/MCP/SMC areas most suspect.

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