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iPhone 6 resets Short circuit, causing the startup screen not to display repair
Machine model: iPhone 6
Symptoms: The screen is not displayed.
Maintenance process:
The customer sent a bare board, describing that the fault PP_GPU VCC is not available, and this VCC will not be available until it enters the system. Directly connect DC power supply with current 0 000 instead of short-circuit current, and directly connect it to 200MA or so according to startup current, without current of change xctc5401, all groups of VCC output by the test power chip are normal, and there is no Short circuit for ground test diode value and CLK reset for VCC.It is found that the reset VCC is only 0.65V VCC is low, and the normal VCC is 1.8V V. The values of the reset test points diode value,385 in the ground test are normal, which seems that the chip connected to the reset is defective, as shown in the figure.
iPhone 6 resets Short circuit, causing the startup screen not to display repair Figure 1.
Display IC and CPU.
iPhone 6 resets Short circuit, causing the startup screen not to display repair Figure 2.
iPhone 6 resets Short circuit, causing the startup screen not to display repair Figure 3.
PMU and USB management chips can only be disassembled one by one. Before disassembling, first test diode value of charging connector USB on the ground. There is a group of abnormal, the normal value is more than 700, that group of values is only 635 and one is 560.
iPhone 6 resets Short circuit, causing the startup screen not to display repair Figure 4.
If it is judged that the USB chip is broken, remove it directly, and replace it with an OK chip when the boot current is up, as shown in the figure:
iPhone 6 resets Short circuit, causing the startup screen not to display repair Figure 5.
iPhone 6 resets Short circuit, causing the startup screen not to display repair Figure 6.
After the change of the boot test, the current is normal, and the boot can be displayed, as shown in the figure:
iPhone 6 resets Short circuit, causing the startup screen not to display repair Figure 7.
