It’s always hard to diagnose screen issues, but most times such problems are just screen related. There’s no real way to help here, unless you got a replacement screen or a replacement logic board it’s quite impossible to give a clear answer. I could speculate, since you did a repair inside the housing, you may have not been properly grounded and a small spark may have damaged either the board or the screen, but I realize it doesn’t help with repair. Unless you can access known good replacements I’m afraid you’re stuck.