my vaio laptop display is dead but it works with external display i change the display but nothing happens
If it works with an external monitor but not an internal then you either have an option set somewhere to to kill the onboard video while externally connected, or your screen is dead.
is there a flicker in the laptop screen when you turn on the laptop? at night time or in a dark room, put a flashlight close against the screen to see if can see something when the laptop is on & not connected to the external monitor as maybe the backlight or inverter died.