iPhone 12 Pro Max Cannot Charge and Stuck at Apple Logo issue repair.
Model: iPhone 12 Pro Max
Announced: 2020, October 13
Defect Phenomenon
- The original screen was damaged and has been replaced with a new one.
- After using it for a few days, the phone just stopped working and cannot be booted.
- Connect with the charging cable, but no response.
Troubleshooting
Disassemble the phone and protect the Face ID module with a sticker.
Then take out the motherboard and check the cosmetics
- there is no obvious trace of repair and maintenance
- no water damage trace
- motherboard did not get deformed
Everything looks fine.
After that, connect the motherboard with the DC power supply machine by the DC power cable， then trigger the boot process, and find the boot current fixed at 400mA.
This kind of situation, based on the repair experience, it must be caused by the chip damage.
To find out the defective chip, we need to separate the motherboard with the heating platform first. Then boot the logic board only to see whether the boot current is OK or not? The current is still fixed at 400mA, so we can make a preliminary judgment that the issue is from the logic board.
Check the motherboard under the thermal image with power supplied, we can see the USB chip get extremly hot.
Repair Process
Then replace the chip with a new one
- remove the chip with the tweezer and hot air gun
since the chip is very close to the PMU, so we need to finish the desoldering process ASAP to avoid the PMU poor soldering.
- clean the pads with solder flux and solder wick
- reball the new USB chip, and ensure each pad is smooth
- solder the chip back to the motherboard
After the USB IC replacement, boot again to check the current curve. Now the current curve is back to normal.
Last but not the least, we can recombine the two layers of motherboard with the heating platform
Test
Assemble the phone to test, the phone can be charged normally, and all the other functions are OK.
Issue get resolved perfectly by USB chip replacement
