I am a Toshiba technician and if you have a dim screen or one that is black or suddenly blacks out,
it might just be a power or battery issue.
Do some troubleshooting.
Check the power connection and see if its loose,
then unplug it and take out the battery pack,
then press the ON button for 20 seconds or so.
Then put the battery back in.
If that doesn`t work,
you could have a burned out visual back light or a loose inverter.
If the problem doesn`t go away,
don`t open the LCD monitor and try to fix it yourself as that will void the warranty.