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A1286 2915 does not power from BUTTON but works!

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    A1286 2915 does not power from BUTTON but works!

    Hello

    Im playing with my honor here.... cant figure out this!!


    Working fine a1286 (2011) macbook 820-2915-A....

    I needed to test a keyboard from another (identical) macbook ..
    The keyboard did not work at all, maybe was bad or incorrect version. no labels at all...so i dont know....

    then, reinstalled everything back to the good macbook , but now does not power on from power button, only from a short to GND at R5016... rest is normal...

    I spent day working on this and this is ridiculous,

    measured continuity from pin5 keyboard connector and was interrupted in his way to the other side: R5710 pin2

    so made a jumper and thought would be ok....but

    Still not powering on , but 3.33v present at R5710 both sides!!

    what is wrong?

    the same laptop powers on well with another motherboard, so it is not a keyboard issue.

    What else can I try? some pictures as reference and schematics provided.

    thanks in advance






    Attached Files
    Marcelo J

    #2
    Re: A1286 2915 does not power from BUTTON but works!

    1) confirm that R5710 is a 1k resistor.

    2) remove the keyboard. Short the logic board Power Button pads @ R5016. Does this work to turn the logic board ON / OFF ?

    3) Then do the same short @ R5710, Pin # 1.
    Does this work to turn the logic board ON / OFF ?

    4) Then do the same short @ R5710, Pin # 2 (with keyboard still out).
    Does this work to turn the logic board ON / OFF ?

    The +3v3 on SMC_ONOFF_L is due to the 10k pull-up @ R5070.

    If the above manual bypass methods work then suspecting a connector / contact issue @ pin # 5 of J5713.

    If you have enough hands, consider to probe pin # 2 of R5710 while pressing down on the keyboard on/off button to confirm it indeed goes low during a press.

    Cleaned the keyboard cable contacts with alcohol ?

    Comment


      #3
      Re: A1286 2915 does not power from BUTTON but works!

      If machine turns on when shorting pin 5 of keyboard connector to ground but not when pressing power button on the keyboard, then keyboard connector or keyboard flex is bad.
      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

      Comment


        #4
        Re: A1286 2915 does not power from BUTTON but works!

        Originally posted by mon2 View Post

        1) confirm that R5710 is a 1k resistor.
        yes it is

        2) remove the keyboard. Short the logic board Power Button pads @ R5016. Does this work to turn the logic board ON / OFF ?

        yes it powers up


        3) Then do the same short @ R5710, Pin # 1.
        Does this work to turn the logic board ON / OFF ?

        yes it powers up too

        4) Then do the same short @ R5710, Pin # 2 (with keyboard still out).
        Does this work to turn the logic board ON / OFF ?

        yes it powers up too

        The +3v3 on SMC_ONOFF_L is due to the 10k pull-up @ R5070.

        If the above manual bypass methods work then suspecting a connector / contact issue @ pin # 5 of J5713.

        If you have enough hands, consider to probe pin # 2 of R5710 while pressing down on the keyboard on/off button to confirm it indeed goes low during a press.

        it goes down yes!! after my jumper (see red line in my above picture)... that is the strange thing here. also the same keyboard connector works with another mother so it is a mother issue

        Cleaned the keyboard cable contacts with alcohol ?

        yes did it before.. no results.
        Last edited by marce002; 07-14-2021, 04:56 PM.
        Marcelo J

        Comment


          #5
          Re: A1286 2915 does not power from BUTTON but works!

          Originally posted by piernov View Post
          If machine turns on when shorting pin 5 of keyboard connector to ground but not when pressing power button on the keyboard, then keyboard connector or keyboard flex is bad.
          nop because same keyboard/connector/button works perfect with another motherboard.
          Marcelo J

          Comment


            #6
            Re: A1286 2915 does not power from BUTTON but works!

            1) locate the ground pad on the keyboard flex cable.

            2) power down and work with the keyboard only.

            3) meter in resistance mode (200 ohms). Red meter lead on pin #5 if keyboard cable, black on the ground pad of the keyboard cable. Press the on/off button. Do you see pin #5 short to the ground pad of the cable?

            4) repeat with the keyboard attached to the logic board. Are the results the same?

            Comment


              #7
              Re: A1286 2915 does not power from BUTTON but works!

              Originally posted by mon2 View Post

              1) locate the ground pad on the keyboard flex cable.

              2) power down and work with the keyboard only.

              3) meter in resistance mode (200 ohms). Red meter lead on pin #5 if keyboard cable, black on the ground pad of the keyboard cable. Press the on/off button. Do you see pin #5 short to the ground pad of the cable?

              4) repeat with the keyboard attached to the logic board. Are the results the same?


              with keyb connected:

              3* no battery no plugged in, keyboard connected , black on pin 29 GND, and red in pin 5 goes from 300/200kohm down to aprox 100kohm .. restarting this measurement goes to 200k again and down to around 130k....weird
              button pressed messed up things , when pressed down to 8kohm , when unpressed goes up to 2 or 3 Mohms.... very noisy numbers, not constant not fixed values, always moving but great difference in res pressed and unpressed...

              with NO keyb connected:


              OL when not pressed and 0,4Kohm when pressed... constant values almost
              Marcelo J

              Comment


                #8
                Re: A1286 2915 does not power from BUTTON but works!

                Are you 100% sure this keyboard is for use with this logic board?

                The pull down is not strong enough with this keyboard to perform the on/off function. The resistance is just too high. If you are really in a pinch and have to use this keyboard, you can try to apply another resistor to ground on this pad. The effect we want is that when you press the on/off button, the resistance from this keyboard in parallel with the external resistor will allow for the function. It is only an idea but should work. The proper solution is to find a better keyboard or a new one. The above idea will require some trial and error.


                Test with another keyboard and check the on/off pad using the same method. Once you can get the resistance down, it will work.

                Comment


                  #9
                  Re: A1286 2915 does not power from BUTTON but works!

                  To clarify on your testing...

                  remove the keyboard off the logic board.

                  Using the keyboard (ONLY) - check the resistance on the ON/OFF pad (red meter lead) and ground on the keyboard cable (black meter lead). This test has nothing to do with the logic board - just the keyboard & meter will be used.

                  Then press the ON/OFF button on the keyboard - what are your resistance readings?

                  Concluding so far that your keyboard is defective or not the proper model for this logic board.

                  The defect could be as simple as some liquid inside the membrane / closure of the button(s).

                  Comment


                    #10
                    Re: A1286 2915 does not power from BUTTON but works!

                    Thanks i will try to lower the resistor and comme t. The keyboard was ok and original since it is from the first macbook... remember this happened after commecting the bad keyboard to the good system as i have stated in my first post.
                    Also remember that swaping motherboards the system starts ok with that same keyboard and same button.....
                    It make sense to lower the res... i will test that.
                    Last edited by marce002; 07-15-2021, 07:27 PM.
                    Marcelo J

                    Comment


                      #11
                      Re: A1286 2915 does not power from BUTTON but works!

                      Yes!!! 10k Parallel resistor did the trick. Thanks mom2 ..thanks to all.
                      Marcelo J

                      Comment


                        #12
                        Re: A1286 2915 does not power from BUTTON but works!

                        Well done

                        Comment

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