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LCD Backlight Turns Off On Windows Startup

Posted on 2007-10-02
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Okay folks, I've researched this a lot but haven't found a solution yet.  This laptop belongs to a client of ours and I'm just trying to get a good installation of Windows going.

The Problem:
When Windows starts booting the backlight turns off.  The LCD is still working though as I can see it faintly.  And I can go into the BIOS, use boot disk utilities like Acronis, Avast BART CD, Ultimate Boot CD without the backlight going off.  I have wiped the disk completely and started installing Windows XP but when the install gets to "Setup is starting Windows" the backlight turns off.

I have been trying various suggestions on the net for a few days now and have to think it's a firmware/software issue more than a hardware one.  Unfortunately I have not found and BIOS updates.

Also something that I find very strange is that the Fn keys do not work outside of Windows.  And then the notebook control drivers have to be installed so the Fn keys appear to be software based and not firmware based like I am used to on other laptops.  So trying to change the brightness / video output during boot up or while in the BIOS is not possible.

Thanks For Your Help,
David
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Question by:DRickey
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Expert Comment

by:souseran
ID: 20001685
If your K series Backlight illuminates during the Sony logo stage as well as lights up while in BIOS setup, you have a voltage supply problem to the inverter board.
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msguru earned 2000 total points
ID: 20001698
Hi.  It could be that the lid switch is stuck down, or broken.  Something to rule out before looking at the software!

Best of luck.
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by:PUNKY
ID: 20001784
Yes, Souseran might right about inverter. However, does it act same if you hook up the external monitor?
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by:souseran
ID: 20001822
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by:DRickey
ID: 20001941
Thanks guys, the lid switch sounds interesting but I would think Windows would act strange if it was stuck closed.

souseran, a voltage issue sounds strange since I can use it all day long if I don't boot to Windows and the display is pristine.  I chatted with Sony and they pointed me to the article but that wasn't any help.

And yes it acts the same with or without an external monitor.
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by:souseran
ID: 20001973
So you asked Sony about the inverter?
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by:msguru
ID: 20002066
Some other thnings to check...
 - resolution, decrease it down one notch, then try two.
 - graphics driver, check monitor settings, multiple display options, advanced options, and finally power management options.  Finally, finally - update to graphics driver (or even try a downgrade).
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Author Comment

by:DRickey
ID: 20002073
No, they asked me to do a System Recovery and ended our chat.  Turns out I can't do that as we don't have the recovery media and can't get into the recovery partition during bootup.

But if there is nothing else I can try I will box it up and send it in.
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Author Comment

by:DRickey
ID: 20002135
msguru, none of that applies really since the display turns off before any ATI drivers are even loaded.  But it could change a chipset setting I guess that might be causing problem.  And since it does it during initial Windows install which is a text screen I didn't check the video drivers.  But switching resolutions could kick it in the butt enough to change state so I will test.

I did check Windows power management to no avail and the BIOS doesn't indicate there is any firmware power management.
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by:PUNKY
ID: 20002153
If it acts same with external, I would think the video is downgrade, try reset bios first.
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by:msguru
ID: 20005533
Hi David, the weird thing is that you can go into "the BIOS, use boot disk utilities like Acronis, Avast BART CD, Ultimate Boot CD without the backlight going off"...  Have you left the system on in all of these for the same length of time as you would have when installing Windows, or now by the the time you start Windows and the backlight goes off?  What I'm getting at is; If you can see the backlight stays on for, say 1 hour, if sitting in the BIOS or after booting Ultimate Boot CD, but it goes off after windows boots up in say 60 seconds - then we should be able to rule out things like the LCD inverter.  One thing that kicks in when windows starts, is its power management - ACPI being the most common.  ACPI would allow the OS to power down the LCD - based on its own rules... that could be that the lid switch thinks the screen is down (depends on the laptop as well - some do this by their hardware) or it could think that it's set to turn of the monitor after 10 seconds of inactivity... you see where I'm going.
Some graphics hardware (and some drivers) also detect when an external monitor is connected and take action on it - like turning the LCD off and outputting signal to the external monior - or outputting to both at once.
Anyway - have a go at the tests above, and see what you come up with...

Best of luck!
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Author Comment

by:DRickey
ID: 20008063
You are absolutely correct.  I did not figure it was an LCD hardware issue because it really looked like the system was turning off the backlight on purpose.  But remember that the first time setup starts Windows is  a couple minutes into the install after it loads some basic drivers . . . one of which is ACPI.  And after your lid switch suggestion it was readily apparent that power management was the culprit.  So I daringly unscrewed a dozen or so screws and plucked the SMD lid switch off the motherboard. After putting it back together I am sitting in front of a fully functional screen.

Thank You For You Insight,
David Rickey
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