I dropped my 4S and when I picked it up the screen was black. there was absolutely NO damage to the outside of the phone that I could see. Even after trying a hard reset and powering down for an hour, it still didn't come on. But I still could hear it ring, text alerts, email alerts and alarms. So I figured something was up.
So, I looked online and found IFIXIT website and did some research. I guessed it was possibly something to do with the display data cable. I decided it wouldn't hurt to try taking it apart and trying to repair it.
I pulled up the tutorial on Replacing the display assembly. I ordered the Liberation Kit. After it came in I printed off all the pages of the tutorial. I started in and everything I took off the phone, I taped to that page's instructions. That way I knew I couldn't lose any pieces and also that each screw went back in the exact spot. I made it to step 17. When I was removing the 5 cables at the top of the logic board, I noticed the display data cable was already popped loose. That would make sense if it was loose and why my screen was black. So I popped it back on, reassembled the phone and gave it a try. It turned on the second I hit power button and has been working perfectly now for almost 2 weeks. I was THRILLED!!!
I am NOT a technical person. This was the first time I had EVER torn apart a cell phone of any kind. I now feel like I can take on other issues my phone might throw at me. I also am going to try taking apart my former 4S that had water damage 6 months ago and never restarted. I would like to see if I can get my pictures off that phone. At least maybe I can use it for parts if nothing else.