iPhone 7 no booting repair after falling

Machine model: iPhone 7
Malfunction:no booting after falling

Received an iPhone 7, fault description when getting off the busmobile phoneFall underground, and it will be no booting after the fall.
Maintenance process:

DC power supply. No Short circuit or short-circuit current was found.switch is turned on, and it is found that the current of DC power supply reaches 1.2A instantly, which can basically be judged as the problem of DC power supply or the BUCK circuit of CPU. Power off immediately to avoid burning of core components caused by continuous power-on.

iPhone 7 no booting maintenance after falling Figure 1.

Check VCC of Nand first,Nand VCC of iPhone 7 has 3V, 1.8V and 0.9V measurement one by one, and found 3V Nand.

iPhone 7 no booting repair after falling Figure 2.

As can be seen from Boardview, 3V is connected with many components, and the motherboard is powered on by Colophony (Solder).

iPhone 7 no booting repair after falling Figure 3.

In the picture, the Colophony (Solder)on a filtered Capacitor melts first, and then it is taken down directly, and the measured 3V is not Short circuit.switch installed is turned on, and the mobile phone is turned on normally.