macbook pro blank display I am facing the issue with my laptop as when its starts its booting and chime sound is present but the display is blank and after sometimes, the display becomes grey. Sometimes it will work fine means display is working perfectly

I tried with changing RAM, reassembled display cable, but sometimes it will work, sometimes not.

My laptop is not in warranty, I checked with the service center they said some issue with either LCD or logic board, so they have to replace and it costs similar to buy a new laptop. 

If I use with an external display, will it work?
I had a similar problem with my Macbook Pro (Not in Warranty). Apple Genius Bar was able to get it fixed in $150. They replaced the logic board and screen. For the time being, using the external display is probably the best choice.