Had a completely black screen - not even a backlight. Had the exact same problem as you after my MBP had fallen off the bed. What is the culprit here? Iris video card, Logic board, loose internal connector, or all of the above? Is the internal display issue and this issue related at all? Then, I must boot into safe mode to use the mac again! And the cycle repeats itself. use keyboard) EVERYTHING GOES BLACK AND TURNS OFF. Here's the question: When I boot normally in clamshell-closed mode, external monitor works perfectly. screen isn't working- that's not the discussion.
Finally, I can use my external monitor! I can get into my mac and mirror displays, so that I can offload my data. mode, and output on external monitor! However, white progress boot bar hangs at 1/2way for 3.6 hours. 'HDMI signal not detected.' Okay, so I do the Googles, read the reddit, etc etc. Apple logo on the back lit up, backlight was obviously working, but ZERO display workings.
Went to boot one day and *chime!* but no screen. A1502, purchased in March 2014, has suddenly created a pretty nasty problem.