iPhone 4s, Black display, but touchscreen and reg functions work?
I had a little humidity get into top ports on iPhone 4s. Managed to unfog/dry out the condensation on camera lens with vacuum cleaner and crevise tool. Power button quit working And proximity screwing up. Kept putting caller on mute or speaker, so I disassembled to see if I could fix. Power button still not working AND black screen. Everything else seems to be working fine.. Just can't see anything to operate phone!
It sounds to me like a ribbon cable may have gotten crimped or cut when it was reassembled. We would recommend disassembling the unit and checking out the cables. Also, make sure all of your connectors are seated properly. Do a hard reset and post the results.