Problem with backlight, or is it something else
My daughter's 4s got wet. I opened it up (thanks to ifixit), cleaned the small amount of corrosion around the connectors near the power switch and inspected for any burn areas. There were none. I also replaced the docking connector as it had suffered with some years of neglect.
Reassembled it, charged the battery and switched it on. Brilliant, it worked, except that after an hour or so the display went blank. Turning off then on produced the same result. After several similar cycles the display stayed off and still remains off. I have since realised that the display is actually on and functioning but only viewable in a strong light.
Classic symptoms of a failed backlight? However, if I do a reset the Apple flashes on as brightly as in the past. Similarly, if the battery is really flat (less that 5%), when I plug in the charger the battery icon comes on to tell me its current state, then goes off.
So how can the backlight not work except at the start of the reset cycle or at the beginning of a charge cycle when the battery is really flat? This infers that the electronics are ok doesn't it?
During the investigations I have stripped the phone several times and restored it to the latest sw with exactly the same results. I am very intrigued and looking for help.
Is this a good question?