Answer to "I have no video; backlight comes on but display is black"The video card is soldered onto the board on the MBP Retina. It can't become dislodged, but it can break. I have a user with this issue on a Mid 2014 15" which is why I'm here. He can get video on an external monitor. Apple will repair for a flat rate mail in, don't let them charge you full price for the part - only do a depot repair.