Screen stays black after putting iPhone into sleep mode

Hi Andrew,

This is a tough one; I haven't heard of this sort of problem before, so you're kind of in uncharted territory.

My suspicion is the replacement screen though. The thing is, OLED and LCD screens have significantly different requirements in terms of signals and power. The LCDs also have a backlight that's not present on the OLED displays, so aftermarket manufacturers would have had to get creative in figuring out when to turn the backlight on and how bright to make it since the OLED screens don't have that requirement.

The good news is that the iPhone X is old enough you can get soft OLED replacement screens at a reasonable price; the last one I got for my granddaughter was only $35 USD off of eBay. Quality looks good to me and it fit and works perfectly, even took the True Tone programming from the old screen. They're out of stock now, but here's the one I bought.

iPhone X SOFT OLED Touch Screen Digitizer Replacement

So my suggestion would be to switch to an OLED screen and reevaluate to find out if the LCD was the problem all along. For this purpose, either a hard OLED or the original soft OLED will both work. The advantage to the soft OLED is that the display is printed on plastic so it can be curved so as to extend all the way to the curved edge of the glass, where the hard OLED is glass and can go really close to the edge but not quite.

By switching back to an OLED you'll also increase your battery life, as the LCD/backlight combo takes significantly more power than an OLED.

That's all I can think of for you to try, Andrews; I'm kind of assuming the phone has been reformatted and wiped, but it couldn't hurt to do a DFU restore just to make sure it's wiped as completely as possible before you start throwing hardware at the phone.

Out of curiosity, does your display settings have a provision to turn on True Tone? I'm wondering whether the LCD screen supports the True Tone programming. Of course, that presumes the person who changed the screen did the True Tone programming; they may or may not have.