laptop screen showing backlight but no display but works fine when connected via hdmi

[Dhrayco]

my laptop built in display monitor keeps showing as unknown device and is displayinng blank i can only acess my pc via hdmi external display, both displays are now identified by my pc as display 1,the display doesnt even come up on my external hdmi display until i close the lid of the laptop and open again b4 it gets signal out. im very sure its not a hardware issue because it came up one day after a reboot i wish i knoew what i did. but then then it went off again after a windows update, i also kno w because when i pug in to power source i can see the backlight increase and when disconnected you can just see it dim down. i have tried everything ossible to get it back up except resetting the bios to default mode and thats because i cant access my bios as my pc screen wont show and my external hdmi wont display until pc is fully booted up. im to scared to try to take out my cmos battery so please dont even suggest that

 

[The Paladin]

I had a laptop do that, it was the signal flat cable that runs thru the hinge from LCD to motherboard that was cracked, usually can get one cheap on ebay to replace it with the service manual of laptop