Hey everyone, running into a bit of a strange issue with my MBP, which I had just sent off to Apple and had the Logic Board replaced due to the Video Chip issue that is notorious with this particular model. Before it was getting lines across the screen and freezing, kernel panic - etc. But...... now. Still a video display issue. Powering On. OS X 10.10 Loading screen appears just fine. *Bar Goes Across* Display goes blank. If I connect an external monitor via Thunderbolt the MBP screen will come on, But then if I disconnect the External Monitor the MBP screen will go off. I can Boot into my Yosemite USB stick and access the installation or Disk Utility just fine, without the display issue. So I'm a little lost on whats going on here. Haven't tried deleting display profiles, or anything at all at this point.