Black screen on toshiba satellite a105 hook up external monitor and it works

[iwoofone]

I turned my laptop on can see logo then it turns black hooked up an external monitor and it works with it can you tell me
what is the problem

 

[ratedk]

Sounds like the backlight in your screen is going out. The backlight is controlled by an inverter, which supplies power to the backlight inside the screen.

To replace the backlight, you will need to replace the entire screen. To replace the inverter is much easier (and cheaper). Figuring out which one it is is not as easily done. A computer repair shop should make easy work of it.