Malfunction Phenomenon
Receive an iPhone 7 with no service after dropping damage.
Trouble Shooting
Normally the no service might be caused by the Baseband and RF relevant circuit.
Since the no service issue happened after dropping damage, first, we should take out the motherboard and check the cosmetic of the motherboard under the microscope carefully to see if there’s any component that gets lost or broken.
After checking, we found the surface of the RF chip XCVR0_RF is cracked.
Replace XCVR0_RF with a new one, assemble and test the phone, service back to normal, problem resolved.
The whole troubleshooting process takes only a little time, but the requirement for handwork experience and skill is high, so more handwork practice like soldering chips, jumping wire, etc. are required.