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February 23rd, 2023 13:00
Latitude 5420 Magnet Question
So it appears that there is a magnet in the lid of the laptop behind the screen.
I have been able to determine that it is not to secure the lid when closed, and it does not seem to be a screen switch for when the laptop is closed. What is it?Tall rectangle in the boxed area appears to be the magnet.
In this picture from the service manual you can see the magnet in the boxed area, it appears to be the tall rectangular piece.
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filbert
4 Operator
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1.8K Posts
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February 23rd, 2023 15:00
I believe that it's part of the mechanism to sense when the display is closed. That enables you to specify what behaviour you want to occur upon display closure, such as putting system to sleep.
ejn63
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February 23rd, 2023 18:00
If you're referring to the metallic tape, it's most likely RF shielding.
Tatolino
6 Professor
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2.8K Posts
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February 24th, 2023 01:00
@filbert wins!
It's the magnet coupled with the Reed switch under the keyboard/palmrest, if you touch the palmrest in the the right position with a magnet you should be able to trigger the action (supposedly the screen and the keyboard backlight turn off, the system turns off / goes into sleep).
It's a similar solution to the Hall switch, but it's 100% passive. I think you'll probably remember years ago how some Macbook users started posting all upset about how placing their phone on the laptop palmrest would cause the laptop to turn off. Or how placing a running laptop on top of a closed laptop would turn off the first laptop. Little guy is the reason why!