Chosen Solution
I just replaced the cracked display assembly of my MacBook Pro 15" Mid 2014. After turning on the MBP the screen stays black. I have checked all motherboard connections as well as the brightness and performed a SMC reset. I then put the display assembly on another MBP to confirm the screen is working and it is on that MBP. So I know the display assembly is 100% ok. To confirm there is no problem with the MBP itself I put back the cracked display assembly and it is working (although cracked). So it seems I have a working MBP and a working display assembly. However when they are combined the screen stays black. What am I missing here? Does anyone have a suggestion or idea?
I suspect the backlight fuse link is burnt. To verify put the new display back on your system and then shine a flashlight through the Apple logo (a poor mans backlight). You should be able to see a faint image of the desktop. The other way is to plug in an external monitor. Update (10/26/2015) Not good :-{ that implies the display is the wrong unit for your system. What is the part number you used?
It seems there are 3 A1398 Display assembly units. I ordered the wrong one (2013/2014 unit for a mid 2015 MB).
