iPhone 6s no turn

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.

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 and PP1V0.