HP8560w DreamColor LCD suddenly went black. PC still running.

I've been using it without any problems until one day I decided to use the sleep function (pressing the sleep button). When trying to wake it up - the screen never lit up. Pitch black. Dead.
I'm looking for some advise that can help me identify the faulty part; The GPU board (NVIDIA Quadro 2000M), the Decoder board or the LCD itself?
If I connect an external monitor to the PC, it boots up just fine and can be used, but the Device Manager only shows the Basic Microsoft VGA Graphic card Driver. This suggests perhaps that the GPU board is defect since it appears not to be detected at all (?).
But is there a way to find out for sure?
If it was the LCD panel itself, I would at least expect the backlight to come on.
The result of a defect Decoder Board is very unclear to me. Would the BIOS be able to "see" if the Decoder Board is defect, and thus ignore the whole GPU during POST?

Also, I was wondering if it is possible to ditch the Dreamcolor LCD and put in a regular LCD instead? Is the output port on the GPU a "normal" eDP port, and can I thus use a regular 30 (or 40) pin cable to drive a regular non-Dreamcolor LCD panel?

Any advise is appreciated. This PC, although old, is still a high end device with 1Tb SSD and 32Gb RAM.

 

Did you try to hard-reboot it?

EDIT:
Ok, I saw you did...
Then you need to try another GPU first.
I doubt that the screen/color board is dead. Sounds like GPU problem

 

And how do I "try another GPU" ?
It isn't like I just have one lying around
I was hoping for som test-software or simple CLI commands that I could use to verify/determine if the NVIDIA board was dead or alive?

 

It is possible that putting it to sleep and resuming corrupted something at a software level. If everything was fine until you did that then a hardware failure would be a very odd and unfortunate coincidence.

Fully updated Windows 10 installations are unstable and unsuitable for use on a system where reliability matters, and you could be seeing evidence of that if all of the latest and greatest updates garbage were applied.

If you try to install an NVIDIA driver does it install properly or do you get an error message about it not detecting an installed product?

If you go to Device Manager and select the properties of the GPU does it have any problem status codes?

 

I agree, The NVIDIA driver has been installed and working just fine - until I put it to sleep. Using an external monitor, it still reports everything ust fine. The NVIDIA driver detects the installed HW and there are no errors presented at all in DM. That's why I suspect the backlight on the screen somehow just suddenly died.

 

Can you see the windows screen if you shine a flashlight at the screen?

If the backlight died but the screen was initialized and working, you would still be able to see the screen under the correct lighting (e.g. with a flashlight or other very bright light source), since the screen would still be on and activated.

 

Since this is a "Dream Color" LCD, I suspected that the flashlight method might not work. But I have tried it without any luck.

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