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820-3437-B bad DC-IN board??

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  • 820-3437-B bad DC-IN board??

    Hi, this is my first repair attempt on a 820-3437-B. The measurement on the G3H Fuse is 8.17V which is too low I guess. So I'm thinking that the DC-IN board might be bad. Weird thing is, that the LED on the charger gave green and orange light, as well as a fan spin some times when I reseated the flex-cable. So the connection seams very fragile there.. What else could it be?

  • #2
    You must get the correct voltage on PPNUS line (aprox 8.5V) even without LIO flex connected.
    Only 5pins DC cable is sufficient to start the board.

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    • #3
      So I`m getting 12,8V on Pin 2 at D7005 where I should be getting 18,5V and on Pin 3 for PPBUS_G3H I'm getting 8,17V where I´suppose to get 8,6V...Bildschirmfoto 2018-09-24 um 10.44.16.png

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      • #4
        "So I`m getting 12,8V on Pin 2 at D7005 where I should be getting 18,5V"
        You make some wrong assumption...
        You don't get 18.5V from 45-60W charger.
        And also forget about R7005, which drops a bit the voltage.
        Even Q7010 and D7005 itself are between charger and U7090 input; where you get 12.8V.

        Post some voltages on U7100; 12, 13, 9, 15.
        Also check voltage and resistance to ground (diode mode) on SCL/SDA pins from J6950.

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        • #5
          Ok, so on U7100 on Pin 12: 3.36V | Pin 13: 3.36V | Pin 9: 3.36V | Pin 15: 07,06mV?? Regarding J9650 : Pin 5 +6 have shortage

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          • #6
            Sorry ment Pin 5 + 4

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            • #7
              "Pin 9: 3.36V"
              Muy mal, SMC thinks about overcurrent through R7020.
              So check R7021/22 and traces to U 7100 ;27/28 should give 020.


              "Pin 5 +6 have shortage
              ---
              Sorry ment Pin 5 + 4"
              STOP to measure in diode mode a powered board...

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              • #8
                Ohh, sorry R7021 and 22 are not available on the 820-3437-B

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                • #9
                  I chekced without power and there are no shorts

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                  • #10
                    No shorts on J6950

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                    • #11
                      I'm sorry too, read R7121/22.
                      You should understood what I meant.

                      Also there is R7120, instead of R7020...

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                      • #12
                        Both(R7121+22) are 10.3Ohms and have full continuity to the Pin 27 and 28 of U7100

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                        • #13
                          R7120 has 12.6V on all four sides

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                          • #14
                            Check again pin9 of U7100.
                            It can't have 3V if there is 20 ohms between pins 27/28!!!

                            "No shorts on J6950"
                            I didn't ask to check for short.
                            Please pay atention to the requests...

                            Comment


                            • #15
                              I'm sorry if this gets annoying for you. I checked Pin 9 again(in Voltage Mode) and it gave me: 31mV. Ok I read out J6950 and here are the measurements: Voltage mode=VM | Resistance to Ground= RG (Diodemode without MagSafe plugged in) --> Pin 5: 3,36V (VM) / OL(RG) Pin 4: 3,36V (VM) | OL (RG) . Both Pins have very High Resistance to Ground when measured in resistance mode as well. Hope I did everything right this time. I'm a complete newby.

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