Motherboard sos beeping while on charge

Hi, long story short, My iPhone 7 died due to an impact, screen and battery replaced with full working ones, when I put the phone on charge the phone screen is still black and I can hear a regular small noise coming from the logic board, every 3 secs, that stops only when I unplug the phone.

Does anybody know the reason and what to do? Is it an easy fix?

The motherboard is warm when is on charge (not overheated)