The iPhone 11 Pro Max is a powerful device, but even the best smartphones can run into issues. One common problem is when the screen suddenly turns black, and the phone refuses to boot. In this guide, we’ll take you through the step-by-step process of diagnosing and repairing this issue. Whether you’re a professional technician or a DIY repair enthusiast, this article will help you troubleshoot and resolve the no-boot problem on your iPhone 11 Pro Max.
Phone Details
Model: iPhone 11 Pro Max
Announced: 2019, September 10
Defect Phenomenon
The iPhone 11 Pro Max suddenly experienced a black screen and could not boot during regular use.
Troubleshooting
1: Initial Assessment
- The phone was previously repaired by another technician. Upon receiving it, the motherboard was already separated. A visual inspection revealed no signs of physical damage or water exposure.
2: Testing the Motherboard
- Connect the upper layer of the motherboard to a DC power supply and attempt to trigger the boot process using tweezers.
- The boot current is fixed at 14mA, which suggests a problem with the NAND chip or CPU, particularly with the power supply rails.
3: Diagnosing the Power Supply Issue
- Use a multimeter to check the power supply rails associated with the NAND chip and CPU.
- After carefully checking the small capacitors around the NAND chip, one rail shows a short circuit. The affected rail is the 1.8V power supply rail (PP1V8_S2) for the NAND.
Repair Process
1: Removing the Shorted Capacitor
- Carefully remove the black glue covering the NAND chip using a hot air gun and a blade knife.
- Identify and remove the shorted capacitor, which is a filter-type capacitor. Since it’s a filter capacitor, it can be safely removed without replacement.
Recheck the diode value on the rail after removing the capacitor, and confirm that it has returned to normal.
2: Reassembling the Motherboard
- Connect the motherboard to the DC power supply and trigger the boot process again. This time, the boot current returns to normal.
- Recombine the two layers of the motherboard using a hot air gun, ensuring a proper fit.
3: Final Assembly and Testing
- Reassemble the motherboard with the housing and other parts, taking care to install the waterproof seal sticker.
- Assemble the screen and press the power button to conduct a final test.
- After testing, all functions of the phone are working correctly. The no-boot issue has been successfully resolved by removing the shorted filter-type capacitor.
Conclusion
Repairing an iPhone 11 Pro Max that won’t boot due to a black screen can be a challenging task, but by following a systematic approach, the issue can be identified and resolved. In this case, removing a shorted capacitor from the NAND power supply rail restored the device to full functionality. For those facing similar issues, this guide provides a clear path to bring your device back to life. Stay tuned for more detailed repair guides to help you tackle even the most complex smartphone issues.
