As we know, on the hardware side, the iPhone 7 no service failure is usually caused by a baseband power supply or a baseband CPU, the baseband power virtual welding or baseband CPU short circuit.
Power down the iPhone 7, use mechanic screwdriver to remove the screws next the iPhone lightning cable, put iPhone 7 on the screen separator for heating, after a while, use LCD sucker to open the iPhone screen. Remove the iPhone 7 display assembly, disconnect the iPhone battery, and then take off the iPhone motherboard.
Now connect the iPhone logic board to a display assembly, and then connect the iPhone motherboard to a DC power supply via the DC power supply cable. Use Tweezers to trigger the J4504 13 Pin to turn it on, the boot current tested is normal.
Use Fluke digital multimeter to measure the power supply of the iPhone baseband PMU to check if it normal or not, after measurement, we found C5630 and C5703 has no voltage, which mean the iPhone baseband PMU power supply is abnormal.
Place the iPhone motherboard to the MJ A22+ PCB fixture, use UD-1200 soldering station and tweezers to remove the iPhone baseband PMU. Use solder wire and hot air gun to clean the solder pad, and then measure the diode data for C5630 again, it's short-circuited, which means this fault is nothing to do with the iPhone baseband PMU.
Now use hot air gun to remove all filter capacitors on this circuit, and then use digital multimeter to measure the solder pad of C5630, it's still short-circuited, which means the fault is nothing to do with the filter capacitor.
Use soldering rework station to remove the iPhone baseband CPU, now measure the solder pad of C5630 again, the data measured is normal, now we confirmed the faulty part is on the iPhone baseband CPU.
Measure the iPhone baseband CPU, it's shorted, because the iPhone baseband CPU can't be replace alone, need replace whole set or motherboard.
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