Some iPhone XR function failure repair cases for reference
Case 1.
Cannot boot and with a large current once connect with the DC power supply.
Use the rosin inspection method, and find it’s caused by C5655 short damage, the capacitor is related with PP_DISPLAY_BL12_ANODE. Replace it with a new one, then the short is gone and the phone can be started up normally.
Case 2.
The speaker only rings once.
This kind of issue normally is caused by the speaker amplifier IC poor soldering. Check the two speaker amplifier IC may take a longer time, so we just replace the two chips (U5102, U4902) together directly.
After that, the speaker function back to normal.
Case 3.
No display.
Defect phenomenon: no display but the boot current is normal.
In this kind of situation, first, we can check the connector and components around it. After checking, find the small inductor FL5752 is missing.
Check the bitmap, it’s related to the PMU_TO_DISPLAY_RESET_CONN_L signal.
So we can jump a wire to test, that the phone can display normally. Then replace a new inductor with the same specification. Issues get fixed easily by FL5752 replacement.
Case 4.
No baseband function after serious drop damage.
For the no baseband issue, we can focus on checking the chips and components related to the Baseband CPU, Baseband PMU, transceiver IC and small components around them.
Remove the shield cover on the BB PMU and transceiver IC first.
(Tips: use a hot air gun to remove the shielding cover slightly, better not use a cutter to avoid the crack damage to chips under the cover)
After that, measure the diode values of the small components around the two big chips.
Luckily, we found the C906_K is shorted easily.
Check the Refox bitmap, it’s related to the power supply of PP_1V3_SMPS3_XCVR_ANA, it’s a filter type capacitor. We can just remove it or replace it with a new one.
In order to ensure the Baseband and RF function works more stable, better replace a new capacitor with the same specifications.