I had a Toshiba laptop screen go dark on me, twice.
Time #1 the laptop was accidently kicked when on the floor.
That time it was a fine ribbon cable connector near the hinge for the screen. It came loose. I snaped it back in and it worked.
Time #2 when it went black.
It was was the fluorescent back light bulb. Got them online for a few $'s.
Now installing them took some time and a quality soldering iron, but in the end it works great.
There also is an inverter that powers the lamp (very high voltage). In my online search people mentioned they go bad. That was not my case so I left it alone.