No power to laptop lcd

[samuraiweasel]

Hey guys, encountered a curious problem today with my laptop.
I had just installed some windows updates and it prompted a restart, so I did.
Everything shut down OK, the on boot, the screen did not come on. No back light, no display, just black.
But it boots up fine, I hear the startup sound, Skype logging in, etc.
My first suspicion is a bad LCD cable as I have had red sometimes when I open it using one hand. But shouldnt the back light come on anyways?
It is an HP DV9205AU with a 7150m.
I have lots of experience with laptops and desktops so opening it up isn't an issue.
Its old so no warranty.
Any advice?

[Steve]

Shut down the laptop and unplug its power cable and the battery for a few seconds, then, start it up. Does the backlight come on before Windows loads and show the manufacturer's boot logo etc?

If it does, but then the screen goes black once Windows boots, a driver is broken - boot into safe mode and roll back using system restore; you can always try the updates again, but maybe check for drivers updates from your manufacturer's website first.

If it doesn't, then it's not related to Windows. Either a cable is broken, or some part of the display is broken (power inverter, maybe).

[samuraiweasel]

Well I don't get any post or bios screen so its definitely display parts that are broken, is there any way of narrowing it down though, because there's the cable, inverter and the actual LCD.
My guess is cable though.

[Steve]

Not easily. I guess if the hinge covers can be removed you could wiggle the cables to see if the display springs to life, but beyond that some disassembly and multi-metering may be required.

Does it still output over VGA OK? It's a bit of a stretch to look at that because a laptop will display its boot logo on the LCD no matter what else it's connected to.

[samuraiweasel]

I tried taking the screen off and wiggling the cable, no luck there. It doesnt seem like the backlight though.
I only have a monitor with dvi at the moment, so tomorrow i go hunting for a converter.

[oldboy47]

Couple of years ago I had this issue with three seperate laptops (2 Toshiba, 1 HP) and in each case it turned out to be the power inverter. Was not difficult and reasonably cheap to replace.

[Sealatis]

Hey guys, encountered a curious problem today with my laptop.
I had just installed some windows updates and it prompted a restart, so I did.
Everything shut down OK, the on boot, the screen did not come on. No back light, no display, just black.
But it boots up fine, I hear the startup sound, Skype logging in, etc.
My first suspicion is a bad LCD cable as I have had red sometimes when I open it using one hand. But shouldnt the back light come on anyways?
It is an HP DV9205AU with a 7150m.
I have lots of experience with laptops and desktops so opening it up isn't an issue.
Its old so no warranty.
Any advice?

It can be 2 things
The lcd flex , its a cable that connects the display to the motherboard , replace to fix or check if its well connected
The second the lcds work with a "thing " that starts them up "Cold Cathode Fluorescent Lamp (CCFL) ", give your lcd a little firm tap with your fingers in the back , at the middle in the lower part it might fix the problem (dont hold responsible for extra damage caused to the screen )