The Xiaomi Mi 12, announced in December 2021, is a sleek and advanced smartphone. However, accidents can happen, and in this case, the phone was severely damaged after being caught in a car door and cracked into two halves. This guide provides a detailed troubleshooting and repair process for this severely damaged phone.
Phone Details
Model: Xiaomi 12
Announced: 2021, December 28
Defect Phenomenon
The phone was dropped into the gap of a car door and cracked in half when the door was closed. Given the severity of the damage, it is uncertain whether the phone can be repaired.
Troubleshooting Process
Initial Inspection:
- The screen is clearly damaged and needs replacement.
- Disassemble the phone to inspect the motherboard. Fortunately, the cracked location is between the motherboard and the battery, and the motherboard appears intact.
Checking the Motherboard:
- Attempt to trigger the boot process with tweezers. The boot current is normal, indicating the motherboard is functional.
- Connect the motherboard to a DC power supply machine to check for current leakage. There is no current leakage.
Assembling for Testing:
- Assemble the motherboard with a new screen to test if the display works. The screen lights up, and the phone enters the system.
- Confirm that the boot, display, and touch functions are operational.
Test the functions
Functional Testing:
- Prepare a new back cover housing and screen. Swap the parts from the original phone.
- Test the phone functions: Wi-Fi, speaker, and Face ID all work fine. However, the fingerprint function fails to add a new fingerprint, which is common after screen replacement.
- Continue testing the front and rear camera functions, which are also OK.
- Insert a SIM card to test signal reception, which is normal.
Fingerprint Calibration
The fingerprint failure is a common issue after screen replacement. To fix this:
- Enter ##6848## on the dial pad.
- Go to the Under-screen fingerprint calibration interface.
- Calibrate the fingerprint sensor using the weight tubes.
- After calibrating twice with different weights, the under-screen fingerprint function works fine.
Conclusion
Despite being severely damaged, the Xiaomi Mi 12’s motherboard was intact, allowing the phone to be repaired. The repair involved replacing the screen and back cover housing and swapping parts. After recalibrating the fingerprint sensor, all functions, including booting, display, touch, Wi-Fi, speaker, Face ID, cameras, and signal reception, were restored.
By following this detailed repair process, the Xiaomi Mi 12 was successfully brought back to life.
