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When closing display lid, How is power cut off to display?

Last response: in Laptops & Notebooks
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February 14, 2013 2:04:48 AM

Hello,

When closing the display lid is there a switch that opens that cuts off electrical power to the display?
Where is it located?
Or is there another sensing method that cuts off electrical power to the display when closing the display lid ?
My laptop is a HP G62-407DX

Thanks,
February 14, 2013 2:08:51 AM

probably a sensor that can tell. maybe using magnets idk
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February 14, 2013 2:10:26 AM

probably a sensor that can tell. maybe using magnets idk
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February 14, 2013 2:12:41 AM

I think the exact location of the switch varies between laptops. I used to have a 2005 Compaq laptop that had a rubber button that I could press separately to make it think the lid was down, but I don't remember if it always turned off the display - I vaguely remember an option to tell Windows what to do when the lid was closed. Newer laptops might have the sensor/switch hidden inside the hinge.
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February 14, 2013 2:12:59 AM

It should be a button like this


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February 14, 2013 2:16:24 AM

@badam Yeah, the button from my Compaq laptop looked similar to that (different color I think), but when I borrowed a Lenovo laptop from work, I couldn't find such a button, leading me to guess that it had something hidden in the hinge to detect when it was closed.
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February 14, 2013 2:19:22 AM

@ mauve yeah I have seen those too, the laptop I have must have some type of internal switch, I just looked up his laptop though and got the image from HP
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February 14, 2013 2:20:13 AM

It entirely depends on the design of the lid and hinge. Some laptops use a magnetic sensor in the palm rest with a magnet in the lid. When the two get close together, the sensor trips. Other laptops use a physical button located somewhere near the hinge.

Of all the designs I have seen, none of them physically interrupt current flow to the display. Instead they signal the embedded power controller on the motherboard that the lid has been closed. Depending on what the firmware is configured to do, the display may or may not be powered off.

If you cannot see a physical switch on your laptop, then you probably have a magnetic sensor or a switch that is integrated with the hinge.

--Russel
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February 14, 2013 2:24:29 AM

badam said:
@ mauve yeah I have seen those too, the laptop I have must have some type of internal switch, I just looked up his laptop though and got the image from HP


No such on off push Button.
Was the image from HP specifying HP G62-407DX
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February 14, 2013 2:28:27 AM

rusabus is right, most laptops now use a magnet. Get a piece of steel and run it around the edges of your sceen and palm rest, you'll find it.
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February 14, 2013 2:29:53 AM

jorb said:
No such on off push Button.
Was the image from HP specifying HP G62-407DX



Actually yeah lol, guess they had variances but dont seem to mention it when talking about the lid actuator switch
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00...

eta:nevermind missed it they do state newer ones have it in the hinge
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February 14, 2013 2:32:49 AM

nvalhalla said:
rusabus is right, most laptops now use a magnet. Get a piece of steel and run it around the edges of your sceen and palm rest, you'll find it.

Would sensing switch be possibly located on motherboard?
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Best solution

February 14, 2013 2:47:02 AM

jorb said:
Would sensing switch be possibly located on motherboard?

If it uses a magnetic sensor, the sensor would almost certainly be on the motherboard. But it is still entirely possible the switch is in the hinge.

That said, I looked at some hinges on ebay and didn't see any that looked like the had an integrated switch, but that doesn't mean anything.

Out of curiosity, why are you asking? Will your display not turn back on? Maybe it flashes on and then off again? Or are you just curious (nothing wrong with that).

--Russel
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February 14, 2013 3:16:57 AM

rusabus said:
If it uses a magnetic sensor, the sensor would almost certainly be on the motherboard. But it is still entirely possible the switch is in the hinge.

That said, I looked at some hinges on ebay and didn't see any that looked like the had an integrated switch, but that doesn't mean anything.

Out of curiosity, why are you asking? Will your display not turn back on? Maybe it flashes on and then off again? Or are you just curious (nothing wrong with that).

--Russel


Mostly curious, My motherboard crapped out and while I had it apart I did not see any micro switches or wires near the hinges.
So if the motherboard does not fix the black screen issue I was going to investigate the lid switch.
Just trying to cover all the bases.

Thanks for reply,
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February 14, 2013 5:18:51 AM

jorb said:
Mostly curious, My motherboard crapped out and while I had it apart I did not see any micro switches or wires near the hinges.
So if the motherboard does not fix the black screen issue I was going to investigate the lid switch.
Just trying to cover all the bases.

Thanks for reply,

If you have a black screen, it might be that the backlight is not powering on. I don't know if your laptop uses a CCFL backlight or LED backlight, but if it is CCFL, it will have an inverter board. That is a common failure point. (Looking on ebay suggests it is probably LED backlit, not CCFL, so probably no inverter board.)

It is possible to replace an LED backlight in some LCD panels, but I wouldn't try. Instead you can replace the entire LCD panel for less than $100. Although there is a good chance that the motherboard will fix it.

--Russel
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February 24, 2013 1:11:10 AM

Best answer selected by jorb.
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a c 244 D Laptop
February 24, 2013 8:34:07 AM

This topic has been closed by Maziar
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