Chosen Solution
Alright so this might be the strangest backlight problem Ive seen on a phone. Hopefully someone has had this similar issue and can shed some light. Got an iPhone 6 screen from a store with full backlight working on one aftermarket screen but no display. Again not dim, backlight is working but display isn’t. Here’s the kicker. Every other screen I try on the phone, including known good original ones, show no backlight at all. Backlight will only show on this aftermarket one that was the original replacement for the customer. I’ve ruled out backlight and am wondering if I should even go into display circuit (which I probably still will) if its having this behavior with every other screen tested. Waiting on word to see if I can restore or not. Any theories?
Here’s a stab in the dark…FWIW… Maybe the backlight circuit is unable to fully drive an “original” backlight but that this aftermarket screen doesn’t need as much juice. For example, the ferrite bead used as a filter may be partially damaged and craps out above a certain current, hence no backlight on the original screen. Conversely, it could be the drive voltage from the backlight driver. You don’t give us much to work with but this is certainly worth testing. Why don’t you report back on what you’re probing and where, maybe that will give us some ideas.
