Dell e1505 won't turn on

[dannycris]

Hi my dell laptop e1505 it wasn't turning on only with a external monitor so i decided to reduce the brightness to 50% so I'm able to turn it on. My questions is what part is defective that is not allowing me to ajust the brightness beyong 50%, every time i go over 50% the screen will go black so have to plug an external monitor to reajusted to 50%. I appriciate your help