Reader John Greeves believes he has a stumper in regard to a mysteriously sleeping laptop. He writes:
This is a weird one but I've run out of ideas. My MacBook Air works perfectly until I put it on the subwoofer that sits next to my desk. When I do that, the screen blacks out and I can't start it again. But if I lift it off the speaker and press a key, the screen lights up. This doesn't happen anywhere else I put the computer. Do you have any idea what's going on?
I think I do. Like all the best things in life, it's done with magnets. A little background:
When you close the lid on your MacBook it goes to sleep. And the reason it does is because a magnet inside the display bezel activates the sleep on/off switch (known as the Hall Effect switch). When you open the lid, the magnet's pull is gone and the switch wakes up the computer.
Inside a typical subwoofer is a fairly large speaker, and that speaker bears a reasonably sized magnet. I will guess that when you place your MacBook on top of the speaker, its magnet exerts enough pull to trip the Hall Effect switch in your laptop. And it won't wake up while sitting on the subwoofer because the switch believes the lid is still closed. That helps explain why it wakes with no problem when you move it away from the speaker.
"Oh right..." the more cynical brand of reader hisses (which is challenging with words that have no "s"). "Magnets. Pfft...."
For those doubters reading along, may I direct your attention to Apple's own Mac notebooks: Magnets in devices may cause computer to sleep unexpectedly. Within this enlightening document we learn that even the small speakers found in the iPhone may be enough to put a laptop to sleep if you place it on the handrest. (Though, quite honestly, I've tried exactly that with my iPhone and MacBook Air and the laptop remains stubbornly awake.)
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