Chosen Solution
I changed the screen and battery on my iPhone X a few weeks ago… the screen worked perfectly until a few days ago when i left it on the charger when i went back to it the screen would not light up but it would make sounds and vibrate. So i opened up the phone and disconnected the battery and screen ribbon cables and reconnected them the phone powered back on with the screen working just fine until it did the same thing yesterday. What is causing the issue is it the screen or is it a motherboard or software issue. Has anyone else encountered an issue like this ? If so what was your fix?
The most likely culprit here is a bad screen. The OLED screens tend to be very prissy and all or nothing. I once broke one just by pressing down on the screen when it was on my bench and I was connecting a charge port with one hand. Any pressure near the bottom of the screen can cause it to go out, especially on refurbished OEM screens. Rule this out with a new screen.
