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

[gernstsmit]

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]

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]

It sounds like the back light controller circuit is fried. It should dim the screen slightly, not go off. If you dimm the screen in windows, does it work?

 

[gernstsmit]

It sounds like the back light controller circuit is fried. It should dim the screen slightly, not go off. If you dimm the screen in windows, does it work?

As long as the cable is plugged in I can dim the screen yes.

 

[Jacozeelie]

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