Chosen Solution
I have a Mid 2014 MacBook Pro retina A1398. It seems I have accidentally damaged the display. I did not turn off my system when I tried to connect the display connector and vertical and horizontal lines appeared on the display, then the problem resolved itself, as a result a black screen appeared in addition backlight works but no picture. Note that when I plugged in the connector, there was a spark.
You shorted out the backlight lines to the data lines, not good ;-{ At this point see if you can get an image on an external display.
