laptop screen turned black but laptop still running
 

My toshiba laptop screen suddenly turned black,but if looking closely you can still barely see what is on the screen, like the screen saver turned it self on, but I restarted my computer many times and it loads up but still no results.
I had this problem about 4 months ago, so i called toshiba helpline and they were very helpful and gave me instructions while on the phone. The guy on the phone told me to shut down the system, unplug it, take the battery out and press ON button for 20 seconds, then realise the finger and wait another minute, and it worked perfectly until now. When I called yesterday, the guy on the phone wasnt very helpful at all, he just said that the light bulb probably needs to be replaced.
I did do what the other guy told me over the phone but it didnt work so i think the bulb that lights the screen is broke.

I was wondering how much would it cost to replace such thing. And also, from reading other threads about the same problem, it only happens when the laptop is not plugged in or something like that, and my battery is dead. It does not work, my laptop has to be plugged in to pwer socket non-stop. Would you have any suggestions what to do?

go to the toshiba power managment and make sure it set to not turn your screen off when running on batteries. Also theres a key combination on your keyboard that will turn off the screen to external, its like FN and then you click one of the function keys on top like F3 for example. Try that while its running.

If it only happens when running on battery power but when it's plugged into a power socket it will boot and the screen doesn't turn black, the most likely culprit is a bad battery.

If that's the case and if the battery won't hold a full charge, the options are to run it only when you can plug it into a electrical outlet or replace the battery.