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820-00281 waterdamage - no image?

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  • 820-00281 waterdamage - no image?

    Hello,
    this 820-00281 was waterdaamaged. Just J4402 and J3300 were burned (Pin 22 and 56). The rest of the machine looks fine. I replaced them and run a jumper for PP5V_S0_T139. Pin 56 on J3300 is just a Testpoint) After that i checked all pins for connection to the pads aswell as for shorts to other pads and to GND. Everything looked fine. So i put it in the ultrasonic tested it and now it turns on (drawing ~1,2A). It spins the fans from the first second and activates the backlight after a few seconds. Also a external mouse stays on and it can charge it now at all 4 ports (at the damaged connector the amp meter didn´t even activate before). The trackpad stays clickable. The problem is that is shows nothing on the screen (an external monitor does not activate at all). So i am stuck here as it could be a problem with the video-out over the USB-Cs, an issue with the ininternal screen communication/power and/or something completely different...

  • #2
    Did you try it without touchbar connected?
    Check DFR_TOUCH_LID level.

    Any liquid sign at J8500?
    Look close to pin 43; that could kill U9850 MUX.

    Can you confirm USB acitivity for sure?
    Use USB pendrive with OSX; if flashes is OK (start with boot menu, or disconnect J9600).

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    • #3
      Thank you for the answer.
      I tryed with everything disconnected - no change.
      DFR_TOUCH_LID seems to be straight 0V
      J8500 looks perfektly fine - liquid only hit the one "wing". The rest of the board looks also like new
      But i could not confirm USB activity (Mouse seems to work but my USB drive (Mavericks is my newest one with an LED indicator) did not light up.
      I did try without Liveboat already - no change...

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      • #4
        If backlight comes on, seems that LCD is recognized.
        Board should work for that; unless gets stuck after few seconds.

        Do PRAM reset.
        Use USB mouse light as indication, instead of chime.
        If you have an USB-C volt-ampermeter, it can help you to detect board activity.

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        • #5
          Mouse light stays on aswell as the fans but i could force a PRAM reset with an external keyboard i think as the backlicht turns of and back on after a few seconds. USB-C ampmeter stays at ~1,4A during the reset. No change so far.
          But the amp meter gives another hint. So the Board turns on but after 5 Seconds the amp reading goes back down to 0A and after another 3 seconds back up to normal. No idea what this means. After that the board stays powered on .

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          • #6
            These new boards are very sensitive to liquid spill; CPU gets damaged so easy.
            Some data lines from inside board can be affected.
            Strange to react at PRAM reset with external keyboard and not for internal...

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            • #7
              My guess is that the internal kayboard (or a few keys) is not working => no reset possible (Caps Lock is also not working...)
              Istn`t there anything i can do - specially as the customer needs the data and it actually turns on now...
              Is target disk mode still possible on these newer ones via an USB-C to Thunderbold adaptor? I already ordered the tool that connects to the lifeboat as last chance but it needs time to arrive...

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              • #8
                Update:
                While i was testing every szenario that came into my mind i also tested with the battery (not for the first time). It charges the battery with 4A and turns on from battery. Is this a model that needs a good battery to work?
                But the interesting part is that it actually istn´t completely dead because it showes me the "empty batttery" symbol if i start it from battery sometimes. If i plug it in or just leave it like this it just stays at that screen forever. So i guess CPU is alive and its charging but something with the video is messed up and the picture is freezing or something. Could this be caused be a problem with CPU/GPU Vcore or something?

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