Chosen Solution
I had a water damaged iPhone 7 Plus, I took the original screen out, charger port, battery and everything else. I replaced it with all new stuff and it was working just fine. Then I tested the old screen on it and it powered up for just a second before shutting down. Now it gets really hot and won’t turn on at all. What happened?
Toasted! You have to clean the board with 99% alcohol in some cases the components are corroded /rusted and damaged that was your mistake you didn’t clean the board and inspected. If you backed everything tru icloud get a new phone if you havent try sending it to a data recovery expert.
