@inminent said in Problem with iPhone 8:

Hello, I hope you are well, I would like to ask a question. I have an iPhone 8 that suddenly turned off (it had enough battery) and wouldn't turn on anymore. I took it apart and tried to reconnect the battery, I put it on charge and it started from 0%... It reached 100% and turned on, but now the lock button turns on the screen but won't turn it off... (and if I hold it down, it lets me turn off the phone) it's very strange... Also the volume down button isn't working properly, what could have happened?

Thank you in advance

Possibly the connector that goes to the lock button or the volume button's circuit board got disconnected during the battery repair process. That is, if the cable hasn't broken... or been damaged, which would be more serious.
I would try to take it to a service center to get it repaired, if you don't want to complicate things too much. Also, if the battery has failed, I wouldn't trust the phone's health very much.

Best regards!!

@Inminent Sometimes GPUs or CPUs emit a kind of "electrical" sound that I can't remember the reason for, but it's not always a sign that something is going to be damaged. The thing is that maybe the sound you heard could be from some other component, but well, to be honest, I think you had bad luck since I have a GTX670 Gigabyte from 2012 and it's still working.

I think in Uruguay there is a Youtuber called Superio whose channel is Zona de Hardware and he teaches some fixes, etc. Surely he would also know how to repair your graphics

You will already tell us how this adventure ends, I hope for the best.

Greetings!