Iphone 6s can't be turned on, when you repaired it once, but no technology is perfect. If you’ve pressed the Power button and the screen won’t turn on or you see an error message, don’t worry. You can probably make it boot again. Now vipprog can demo the process of iphone 6s can't be turn on after replacing the camera power supply chip. Hoping you can benifit from it.
The camera cannot take photos, so the customer changed camera 2.85V power supply chip U3200. After turning it on, it immediately turns off. When receiving the iPhone and testing, it cannot be turned on.
1. After connecting adjustable power supply, there is no electricity leakage. Short connect it and turn it on to trigger the signal BUTTON_HOLD_HEY_CONN_L (picture 1-1). There is no current. Measure the power button signal and there is 1.7V voltage, which suggests that the standby circuits and trigger circuits have no problem.
2. Connect adjustable power supply to energizing motherboard and use USB cable to connect iPhone and computer. Based on the iPhone design principle, after plugging USB cable, iPhone will turn on automatically. If this design works, then we know that the trigger circuit is damaged. After plugging USB cable for 2s, if the current is small when turning on iPhone, the USB cable supplies it power. Therefore, we cannot see the current display on ammeter. That is to say, we cannot check the state of motherboard through current.
3. After plugging USB cable, the motherboard still cannot be triggered on. So we guess that CPU is pseudo soldering. Remove the shield cover and observe the surrounding area of CPU under microscope, finding no explosive tin balls and any bump on the surface of temporary storage of CPU upper board.
4. According to the previous repairing experience, that iPhone cannot be triggered on is because the power supply U1202 and CPU U0201 are damaged. Use the diode gear of multimeter to measure the CPU power supply and MIPI bus of display and camera circuits. In this way, we can judge whether CPU is short connected or pseudo soldering, and decide that power supply is fixed first or CPU first based on the measuring result.
5. The diode data of the voltage of CPU power supply PP_CPU is 0 while the normal one is about 15. Observing the capacitors at the surrounding area of CPU under microscope again, we find that a filter capacitor C2001 offered power by PP_CPU turns white, which is very different from other capacitors besides it. Comparing it with the other iPhone 6S, we find that the normal capacitors are deep yellow. Pry up capacitors C2001 and measure, the diode data to ground of PP_CPU is 14. The capacitor C2001 in bitmap is shown in picture 1-2.
6. Plug power supply and trigger it on. IPhone can be turned on and the current jumps normally. Trouble is removed.
7. The power supply of iPhone 6S will not be triggered on to protect itself when its subordinate circuits are short circuits. During the repair process, we may observe under microscope carefully to save twists and turns.