Elitebook 8540w problems wonky backlight problem

[Pampres]

Hi.

I am a collage student scuffeling thou the trenches to get my degree and my YE-old elitebook hand-me-down laptop have started to do some wonky things.

I needed a new laptop due my old beeing way to old, and since my budget is tight i got to scuffle thou a family members bin of old computer stuff. (he works for an a bigger electrical engineering firm so he does have a lot neat stuff he don't use anymore)

Anyways, after popping in an new SSD in it that i had floating about after my last IT job (had to remove the old HDD for obious reasons) and installing windows and a small bucket of random drivers, not all worked as they should in win10 as they were win7 drivers, it worked fine for about a week.
But, after that week the backlight did not turn on regardless of what i did. but in a fit of frustration i pulled the entire ting compleately apart and put it back together and it somehow worked again for a couple of days.
Uintil yesterday, i tried to take it apart again like last time, but it did resolve the issue. I tried all kinds of reset stufflike taking out the battery and holding dow the power button, but no...
So as a last ditch i tried to plugg inn an external monitor. And i got a perfect picture on the external monitor, 10 secounds later the Laptop backlight turned on like normal. So i guessed it was a driver issue, and swapped out the driver to the latest direct from nvidia (it has quadro card) and the issue seemed to be fixed.

But wait! the darn thing did it again today! YAY!
And, as soon as i plugged in an external monitor the backlight tured on on the laptop also.... -_-
I can plugg out the external monitor and everything works fine. I can even turn it off leave it for 5 min and tur it on again and it still works fine without plugging in the external monitor.

Anyone got a clue what it might be?

( i am going to try an older driver now just for the hec of it)