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Repair information and guides for the long-awaited refresh of the popular MacBook Air, featuring Intel's Core i5 processors, an updated Retina Display, and numerous other changes and updates that was released on November 7th, 2018.

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Internal screen does not turn on after closing and opening lid

After replacing a failed battery with an ifixit one, the computer wakes up, but does not light its internal screen after the lid has been shut once. The computer does "wake up" and this can be proved by connecting an external monitor. Notably, if you look in Preferences --> Display, the computer does not seem to even know it has an internal screen after re-opening, just the external one appears. No unplugging, or manual sleeping or autoboot disabling solve the problem. The only way to come back from this condition is to turn off the computer.

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I wonder if it's something with the trackpad/keyboard cable. Or the microphone assembly. According to the schematic, the microphone houses the other hall effect sensor. It actually looks like the way this circuit works is that both hall sensors feed into a logic gate, which then transmits the signal to the SMC to indicate the lid is open. Or closed. But the information from the mic is likely coming through the IPD cable (the one that is for keyboard and trackpad) since the mic connector is on the same PCB as the keyboard circuitry.

I have no idea what the logic table for this gate looks like. So if it's only getting the open signal from 1 of the 2 sensors, it may not send through the "I'm open" signal. Long story short, make sure that cable is seated properly to all connections, but particularly the ones to the logic board itself, and the one underneath the logic board, which connects it to the keyboard. As well as making sure the mic is undamaged, and the cable is seated properly.

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EDIT: On further examination. this logic gate likely transmits lid sensor data through to the trackpad/keyboard so they can be available for use when the lid is open. I also had a look at the data sheet for the logic gate itself, which indicates that it is set to allow voltage through in the case that both inputs are present. OR in the case that the A input is present, but not B. But not the other way around. So if B is present, but not A. The gate does not open. I am not certain in this case which is A and which is B. And ultimately the SMC recieves this data as well. So it may have similar programming. I would still check these cables regardless.

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Apple uses a Hall Effect sensor to sense the closed lid condition. In this series I'm lead to believe its hidden within the Right Speaker assembly you'll note the extra contacts on the connector when compared to the Left Speaker

Make sure you first see if the cable is damaged and if reseating the cable fixes things.

Next I would take a steel paper clip sliding it on the displays face to identify the magnet held within it. Then carefully folding the lid down so you can locate the location within the uppercase the Hall sensor sits (don't close the lid fully as you will damage things). Now using a rare earth magnet you should be able to alter the Hall sensors state by sliding it across the location you ID'd. If not then you need a new speaker unit MacBook Air 13” Retina Display Late 2018 Right Speaker Replacement

MacBook Air 13" (Late 2018-Mid 2019) Right Speaker Изображение

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MacBook Air 13" (Late 2018-Mid 2019) Right Speaker

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MacBook Air 13" (Late 2018-Mid 2019) Left Speaker Изображение

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MacBook Air 13" (Late 2018-Mid 2019) Left Speaker

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Unfortunately, this did not work. Still has the same behaviour after right speaker replacement AND Monterey upgrade. We've determined that the screen is on, it's just the backlight that does not restart. I can pass a magnet over the right side of the computer to get it to turn off, but I've found no means to make it turn back on. I'm open to any further ideas.

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@Steve - The hall sensor is like a switch. The transition between the magnet being near vs removed alters the state from on and off. The signal is sent to the logic board to then trigger the MOSFET power transistor which is what alters the flow of the backlights voltage. I wish you had first tested as I described that would have saved you some time and monies for a not needed part.

At this point you need to review the schematics and board view drawings to trace out the logic.

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We did try and follow your advice, which allowed me to turn off the screen but not get it to come back on. This machine has been barely used and sitting on a shelf for most of its life, it seemed (and still seems) really unlikely that a logic board component would just up and fail like this so we clung to the hope that it was the switch. It would appear that we've exhausted all possible solutions other than a logic board repair.

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@Steve - components also fail do to age! Likely a capacitor has drifted.

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Steve будет вечно благодарен.
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