Chosen Solution
Hi, My iPhone 6 started intermittently suffering no backlight, although the phone still worked and the springboard could just about be seen with a torch shone on the screen. The backlight would randomly work when I took the phone out of my pocket and pressed the home button, and that intermittent state lasted a few days. The fault then became permanent. I’ve checked the backlight inductor and diode. Inductor looks okay with no overheating and reads short as it should. The diode measures infinity in one direction, volt drop of about 0.6 in the other, so is reading normally for a diode. All fusible links (FL****) are reading short. FL2024 is reading a constant voltage of 3.8v (battery voltage) instead of the higher voltage expected. I’ve got schematics and board layouts with pin connections, but without a circuit description I don’t know what starts U1502 switching and producing the higher anode voltage. Has anybody come across this fault with the above readings? Is it likely to be U1502 backlight driver IC, or is chestnut U1501 display IC implicated? I’d rather not change U1502 if not necessary because of expense and the original being surrounded by hard epoxy that’s spread from the CPU, which is also around the inductor and diode. This phone has never got wet. The fault started out of the blue. Thanks.
U1502 backlight IC was the culprit. Went through five of them from AliExpress which were all faulty, so beware. Bought one from a UK repair centre on eBay that uses the supplied ICs in their own repairs and it fixed the backlight. However, the phone now loops on the Apple logo continuously. I have no idea why. I’ve just changed Tristar but it’s still looping.
