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661-06279 Strange Behaviour

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  • 661-06279 Strange Behaviour

    Received an A1707 2016 touchbar 15" in yesterday (820-00281 / 661-06279) with a stange fault. Customer states they dropped the Mac and afterwards it wouldn't power up - can confirm there is a big dent on the corner of the housing.
    I've opened it up pulled the battery and then reconnected - when I connect the charger the fans start spinning and the machine powers up - i see the apple logo load up to half way then the screen goes black but the touchbar remains lit and caps lock reacts when I press it on and off. Also if I press keys it's making the invalid operation noise. If I attempt to force power down the machine at this point it doesn't react - holding power button down for 15 seconds and nothing machine stays on.
    I've disconnected the battery again and done some more digging around - observed the left option key was jammed down with something so have pulled the keycap and removed the offending dirt from there - tried booting again only this time it starts up normally takes me to the login screen no problem at all. Use it for a bit - checked all keys on keyboard working no problems there wifi, bluetooth all functioning as is screen. Shut it down, power it up again a few times - again no issue starts normally so i think great it's just the sticky option key which caused the issue and I replace the bottom case and try to power it up again - it's now behaving in the same way it was originally - it gives me half a loading screen and then blank and will happily sit there ignoring my key presses for SMC Reset, PRAM reset and won't power off with the power button.
    I've done some more to try to get it back on again - disconnected and replug battery a few times and have now managed to get it back on again - currently backing up the customers data in case the board is toast.

    Does anyone have any ideas on what could be causing this issue and what to check for - one of my thoughts would be perhaps there's a faulty lid sensor somewhere but this board doesn't want to power up at all unless everything is connected which makes diagnosing this pretty difficult!
    Last edited by CRC2018; 3 weeks ago.

  • #2
    Test the board alone, using only an USB mouse, or OSX pendrive to confirm activity.
    See if you can turn it on/off with the onboard power pads, R5226, or SW5200.

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    • #3
      It appears to react with usb mouse when it's on it's own without anything else connected.
      Just as an update with more testing I did - after taking customers data off i've left it in a normal open position but off for the whole weekend turned back on and then off no problems shutting down or starting back up. Done this maybe 15-20 times - then after shutting down I closed the lid and reopened - nothing no response at all macbook sits there and won't power up at all no fan spin nothing.

      After pulling the battery again and then leaving it in an open position and plugging the battery back in - i've also connected an external display to try to do further diagnosis, started up normally both displays working - i then closed and reopened the lid - internal display went off but external remained on. I've then checked SMC_LID at c4490 which is reading 3.40v when the lid is open and 0.0v when closed. I've then gone into the display preferences and it can't see the internal display any more.

      Now my thoughts are pointing towards maybe the good old crap screen cable problem on the touchbar models with a data line which isn't talking properly back to the SMC from the screen. Any other thoughts - unit was working perfectly on external but won't power on again now after shutting down - power button presses are ignored, as is shorting SMC_ON_OFF_L to ground - can confirm it drops from 3.40v to 0.00v on power button press however. Also with the internal display completely disconnected it will consistently power up upon application of the charger cable when it's plugged to an external display.

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      • #4
        So the on/pff problem only appears when the board is in the case?
        Start testing the board in case alone and start connecting the cables one by one.

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        • #5
          no the board ignores on off request regardless whether in the case or not - it'll consistently turn on when charger is connected but ignores the power button whether inside the case or outside. With the screen attached it doesn't even turn on consistently with the charger however - all testing done with screen disconnected. I've ordered a new screen assembly to try as I don't see what else I can check at present
          Last edited by CRC2018; 3 weeks ago.

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          • #6
            Try FULL new BIOS, just in case.
            Board should turns on/off with power pads without LCD connected.

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            • #7
              Don't suppose you have a link to a known good full BIOS for this board? I can't seem to find the right one!

              This board is really strange - if I get it working and don't open/close the lid it's working 100% perfectly responding to power keys no problem, the second I open/close the lid it goes back to this behaviour!

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              • #8
                Think i might have nailed down the problem - I decided to use a magnet to individually trigger the SMC_LID sensors - when I went near two of them (the touchpad and left side one) it behaved normally. After I went close to the right side one the problem occurred again. Can it be removed with no ill effects or are these sensors compatible across models as I do not have any touchbar donor boards at present?

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                • #9
                  You can disable one sensor; machine should still work correctly.

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                  • #10
                    So I tried to pull one sensor out and got the same behavior again - in fact it seemed fully stuck in lid closed mode. So i've pulled off U5255 and wired SMC_LID directly to PP3V42_G3H now testing it and so far so good. Probably U5255 has gone faulty

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                    • #11
                      So i'm back to the same stage again today - was working perfectly yesterday and now it's behaving as it was before - booting only to external display like the lid is closed. I would presume at this point we're looking at a problem with the SMC itself as it's the only thing I can think of which would control everything and giving the instructions that the lid is closed and don't send video to internal display. Is there anything wrong with my thinking at this point?

                      Comment


                      • #12
                        TP/KB and Touchbar also blocked in that moment?

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                        • #13
                          actually no the touchbar and touchpad/keyboard are working fine when it's in this mode

                          Comment


                          • #14
                            Bad SMC_LID signal should also disabe TP.
                            If still works, then is not an issue with SMC_LID; unless broken trace, with lost connection on some points.

                            Missing image and backlight on internal LCD at same time?

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                            • #15
                              ultimately I gave this one back to the customer as it was in a state where working reliably on the external display only - i was missing both backlight and image on the lcd initially then after plugging external was just missing backlight.

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