Chosen Solution
While the Iphone 6 was still powered on I unplugged the screen from the logic board and now I can’t get anything to show up on the screen ( I have tried multiple screens that work). Each screen is showing black and the backlight doesn’t come on. The phone still turns on with itunes and I even restored it so I know the phone works. Has anyone experienced this before?
What you did is blow up something on the back-light circuit. You have cathodes, anode, diode, inductor, and backlight driver. Some of those will require replacing. This is perfectly repairable with the proper tools, skills, and troubleshooting knowledge. We do it all the time. It is not, however, a DYI job or even a normal repair tech unless you have micro soldering skills and tools. You can swap boards, no problem. Provided the replacement board is fully functional and iCloud lock free.
Unfortunately, it sounds like you blew a filter or fuse. You are going to need to inspect the board and find the damaged component to replace it. How are your micro soldering skills?
Do a hard reset. (Home + lock button until apple logo appears)
Had a similar issue. Maybe worth a look. Screen does not light up, back light still works
