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No trackpad or keyboard on 820-4924.

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  • No trackpad or keyboard on 820-4924.

    I'm struggling to figure out what the final piece of this puzzle is. I've restored endless voltages to this very wrecked board and it boots with everything functioning normally now expect the trackpad and keyboard are unresponsive. No caps lock light. I'm comparing the circuits to a known-good board pulled from a computer with a cracked screen and I can't find any difference in voltage or diode measurements. Any thoughts on good places to look next?

  • #2
    Try another trackpad and cable...

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    • #3
      Thanks, sorry, forgot to mention that I've done all the basics. I've installed the known-good board and the keyboard/trackpad work normally.

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      • #4
        press power button and hold alt key, does it go to boot selection screen???

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        • #5
          no, nothing

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          • #6
            Voltage on pin 1 and 27 from J4802??? SMC_LID??

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            • #7
              All are good. 3.3V on 27 and 12.6 on 1. SMC_LID is at 3.3V. I checked it at all points. No breaks in the line - it's getting to the trackpad circuit.

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              • #8
                Check power to U4820/30. Does the trackpad start to click once powered on?

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                • #9
                  Yes, PP3V3_S4_TPAD is there. The voltages around U4820 and U4830 are all the same as the good board. The forcetouch click does turn on when the computer comes on but the trackpad button doesn't do anything when clicked. The trackpad is not recognized under System Preferences. Power button is all that works.

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                  • #10
                    Connect external keyboard and go into boot menu and see if KB/TP does anything.

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                    • #11
                      No, nothing at the menu. Only the external works. No internal trackpad, keyboard. Also, no caps lock light.

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                      • #12
                        Inspect connector on the board for corrosion/damage. Must be corrosion around there somewhere.

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                        • #13
                          Ok, I'll check that again. Could this possibly be a bad U4830? Or one of the other chips along the bottom that were hit pretty hard by corrosion? The voltages around them are good but I'm not sure what that means as far as them doing their job.

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                          • #14
                            I doubt that U4830 could mess it up. It could mess things up if the SDA/SCL lines are shorted maybe. The trackpad will probably work without them, but never checked so not 100% sure.

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