Sorry for the delayed reply as I was away.
If nothing is displayed on the LCD or external monitor, perform the steps below:
Unplug the adapter and the battery. Press and hold power button for 20 seconds. Plugin the adapter. Press and hold "D" and turn on the system.
You should get some solid colors to appear on the screen. If you get the solid colors on the screen, LCD is working fine else it needs replacement.
If the LCD is working fine and the display is not working on external monitor, system board needs replacement.
Thanks & Regards