Question Asus F555UA laptop screen dies when power cord is unplugged, even when in the BIOS configuration screens ?

gernstsmit

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Feb 16, 2010
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Hello, I'm an IT technician/administrator for the last 10 years, but today I have seen a first, for me. I replaced a hard drive with a SSD and did a clean install on an Asus F555UA laptop. When I removed the hard drive, and before installing the SSD I turned it on to have a look at the boot settings in the BIOS. I unplugged the power cord to check if the battery is charged and connected properly. As soon as I disconnect the power cord the screen dies, going completely black. However the power LED stays on. When I plug the power cord back in the screen turns on again.

Note that this is in the BIOS with no operating system installed on the laptop. This is also not a brightness setting as the FN+Brightness keays has no effect. The screen goes completely blank and comes on just fine when the cord is plugged in.

Any suggestions are welcome.

What I have already tried:
  1. I bent the pins that connect the motherboard to the battery slightly to ensure that all the pins make good contact with the battery.
  2. I have unplugged and re-plugged the screen cable on the motherboard in case there was some form of bad connection.
Both of these had no effect.

I have now installed a fresh copy of Windows 10 and in Windows it does exactly the same. Just for being extra careful I did check the windows settings. I cannot adjust the refresh rate, only 60Hz is available. Sleep mode is off in the power settings.
 

gernstsmit

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Feb 16, 2010
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Update: I have just noticed that when the screen goes blank, it is actually not blank. It is only the backlight/LED lighting of the screen that dies. If you look closely at the screen onder normal lighting you can just barely make out the image on the screen. I can actually watch the "brightness slider" move around as I "adjust the brightness" of the screen :-D.

If I turn off the light in my office so that the room is dark, then I can't see anything on the screen at all. So there is no light being output by the screen.

I think this might be a hardware issue. I will try to disassemble the screen and have a look at the cables.
 

Jacozeelie

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Mar 1, 2019
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It seems that a switch, a tiny transistor, that switches power from charger to batery is fried. Maybe you can find a secondhand backlight with circuitboard, that you can replace it with. Other than that, i dont think you can do much
 

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