Some people said his iPhone 6 can’t connect to the computer, and the i4 software displays nothing. It’s very annoyed him, because he can’t send photos and videos or others to his computer. Now, let’s see what’s going on this iPhone
First we exclude the problem caused by Tail charger connector. Replace charger connector directly and test, but the problem still exists. We can sure the charger connector remains workable. Then we check the circuit between CPU and the C charger connector. CPU controller will transfer the circuit. View the circuit diagram of USB manager U1700 and find its working condition and data transmission bus, as shown in picture 1-1.
Second, measure the power supply of PP1V8_SDRAM and PP3V0_TRISTAR of USB manager U1700 and 5V power supply of PP_TRISTAR_PIN transferred by Charge Jack. Find the pin 1 of C1739 of PP1V8_SDRAM near USB manager U1700 (picture 1-2).
The material object of C1739 is shown in Picture 1-3. Measure the power supply of the pin 1 of C1739, which is 1.8V.
The pin 1 of C1700 of PP3V0_TRISTAR near USB manager is shown in picture 1-4.
The material object of C1700 is shown in Picture 1-5. Measure the power supply of the pin 1 of C1700, which is 3V.
5V power supply PP_TRISTAR_PIN is the pin 1 of C1704 near USB manager, as shown in picture 1-6.
The material object of C1704 is shown in Picture 1-7. Measure the power supply of the pin 1 of C1704, which is 5V.
Third, as the power supply of USB manager U1700 is normal, we replace the USB manage chip first. But the problem remains the same. Now we measure the diode data to ground of USB cable bus. The measuring point is shown in picture 1-8 and measuring material object is shown in Picture 1-9. Using multimeter to measure the diode data to ground of four signals 90_TRISTAR_BI_E75_PAIR which is used by USB manager to connect Charge Jack, and the diode data to ground is normal.
Fourth, Measure the diode data to ground of two signals 90_AP_BI_TRISTAR_USB which is used by USB manager to communicate with CPU, and the diode data to ground is normal. The measuring point is shown in picture 1-10 and the material object is shown in picture 1-11.
Fifth, continue to measure the diode data to ground of accessory power supply PP_E75_TO_TRISTAR_ACCI which is used by USB Control manager to connect Charge Jack, and the diode data to ground is infinite. The measuring point is shown in picture 1-12 and the material object is shown in picture 1-13.
After checking the PCB bitmap, we know that PP_E75_TO_TRISTAR_ACCI is connected to inductor FL1854 which is shown in picture 1-15 and material object is shown in picture 1-16.
Finally, Measure the two pins of FL1854 and the two pins are disconnected. Replace FL1854 and measure the diode data to ground of PP_E75_TO_TRISTAR_ACCI, which is normal. Assemble the board to Measuring assembly and turn on iPhone and get into IOS to test. It can be connected to i4 assistance after insert USB cable. The iPhone 6 can back to normal work.