A few days ago I was using my laptop as usual and suddenly screen went white but the background sound was still there, I restarted the device but there is noting on screen but white, I opened the casing and checked the connections they were fine and there was no sign of corrosion or short circuit, the graphic card is fine because I can use it with an external monitor, I was wondering what can cause this or is there any way to fix it without the need of a new lcd, the device is Lenovo E540 its a little bit old but had no other problems until now.