Chosen Solution
Hello, i have problem with my iPhone 6 16GB. Yesterday everything working good, in night it was on charger… And at the morning it wasn’t possible turn on. No answer, only black screen. I try too hard reset and connect to PC, but still nothing, only black screen. I have too one iphone 6 icloud lock, i try change logic board, but when you put this logic board to this iphone for parts still no working, when i put icloud lock logic board to this second iphone, it was good. so some issue must be with logic board. But i don’t know what next. I don’t know how i can check what is wrong with logic board. From outside look normally, nothing wrong. Please help me … Thanks
You have properly determined that the issue is with the logic board. Because it failed overnight while charging, the issue is related to the charge circuit. What kind of charger are you using? Cheap chargers can damage the charge circuit. When dealing with a “dead” phone, there is no “silver-bullet” solution. You have to probe the board to get a better understanding of what is working properly and what is not. It may be a simple solution or a complex one. Sometimes we see a visibly blown cap, replace and all is well. Other times, everything looks perfect yet the phone won’t boot. You have to start at the beginning and check PP_BATT_VCC, PP_VCC_MAIN and PP5V0_USB. I would start by checking to see if those rails are shorted to ground. If one of these rails is shorted to ground, then you will need to identify what is causing the short. It could be a bad decoupling capacitor, conductive debris or defective IC that is directly supplied by those rails. If you are measuring the proper voltage, then you move onto the PMIC and check the voltage rails it generates. The PMIC generates ~15 voltage rails. They are all important (for obvious reasons) but the ones to check first are as follows: PP_CPU & PP_GPU PP1V8_SDRAM & PP1V2_SDRAM PP_VAR_SOC & PP0V95_FIXED_SOC PP3V0_Tristar & PP3V0_NAND PP1V8_ALWAYS & PP1V0
