If you’re an adventurous spirit who loves to take your gadgets on thrilling escapades, you might be familiar with the gut-wrenching moment when your beloved device takes a tumble. Such was the case with a OnePlus 8T that met its match on a rugged mountain climb. Despite initial resilience, the phone soon succumbed to its injuries, leaving its owner with a device that refused to power on. In this blog, we’ll delve into the steps taken to diagnose and repair this drop-damaged OnePlus 8T.
Phone Details
Model: OnePlus 8T
Announced: 2020, October 14
Defect Phenomenon
The phone was drop-damaged while climbing a mountain. The rear cover was slightly deformed, and the glass lens cracked at the corner. Initially, the phone still worked, but two days later, the screen blacked out frequently and eventually the phone couldn’t be turned on.
Troubleshooting Process
Initial Inspection:
- The rear glass is cracked and slightly deformed, but the screen is intact.
- Disassemble the phone by heating the rear cover at 100℃ for 2 minutes to soften the adhesive, then separate the rear cover. Protect the rear cameras with stickers.
- Remove the motherboard and inspect it. The motherboard is slightly deformed but has no prior repair traces.
Basic Checks:
- Measure the diode value on the main power supply, confirming there is no short.
- Solder a test wire onto the motherboard for connection to a DC power supply, allowing for easy voltage application and testing.
DC Power Supply Test:
- Connect the motherboard to the DC power supply. There is no current leakage.
- Press the power button to trigger the boot process. The current remains fixed at a very low value, and the phone cannot boot.
Diagnosing the Issue:
- Based on the symptoms, the issue likely stems from an inductor’s poor connection or a damaged power IC.
- Inspect under a microscope and find no obvious inductor pseudo-soldering. Focus shifts to the power IC.
Power IC Replacement:
- Fix the motherboard on a PCB holder and remove the protective sticker around the power chip.
- Measure the diode values of the resistors around the power IC. They are normal, but this does not rule out power IC damage.
- Apply solder paste flux to the chip, then use a hot air gun to remove it.
- Clean the bonding pads with a soldering iron and solder wick, then clean with PCB cleaner.
- Align a new power IC chip and solder it back in position.
Testing and Assembly:
- After replacing the power IC, connect the motherboard to the DC power machine. The boot current is now normal.
- Remove the test wire from the motherboard, reassemble the phone, and test all functions.
- It can be turned on normally and all functions are working.
Summary:
The phone’s inability to boot was resolved by replacing the PMIC (Power Management IC). After the replacement, the phone turned on normally, and all functions were tested and found to be working correctly.
