Use phone opening tools to disassemble the iPhone 6S, open the iPhone screen, and then measure the iPhone 6S by DPS-305 DC power supply. As we can see, the iPhone standby current is normal, no leakage phenomenon. Trigger the iPhone 6S, the boot current jumps normally, which means the iPhone 6S is turned on properly.
Use digital multimeter to measure the resistance value for the display condition of the iPhone display connector. When measured the J4200 display connector 41 Pin, the resistance value for PP5V7_LCM_AVDDH_CONN display screen +5.7V power supply is 0, which is abnormal.
Log into the ZXW Dongle to check iPhone 6S schematic diagram, we suspected that the filter capacitor on the power supply circuit is damaged or the display power supply IC U4000 is damaged.
Now measure it again, but the value is still abnormal, it's short-circuited. Apply some rosin to the motherboard, and then supply power to it, the filter capacitor C4201 melts first, now we confirmed C4201 is damaged.
Use 861DW soldering station and tweezers to remove the C4201, and then measure it again, the resistance value is back to normal.