Follow this guide to fix the problems of iPhone 6 Plus won't turn on. This guide offers you a very detailed logic board repair solution of the problems which iPhone 6 Plus won't turn on after falling. If you want to learn more about iPhone logic board repairing guide, follow the more comprehensive version that covered most of the iPhone model visit HERE.
Failure Phenomenon：
There was no reactivity when pressing the power on the botton and the iPhone failed to start up.
Maintenance Procedures:
Disassembling the phone and taking out the motherboard. Charging the main board with DC power supply but there was no reaction when triggered the boot pin with tweezers.
Measuring the power supply of boot pin by multimeter and the ground impedance values of each power supply. The boot pin had 1.8V and we noticed that PP1V8_SDRAM, PP1V2, P1V2_SDRAM were all short circuit to ground.
Founding out the parts using these voltages according to the circuit diagram, then taking them down one by one to eliminate the short circuit, as shown in Pic 1-1. It was found that the ground impedance values of PP1V2 were normal again after we removed the power supply chipset.
The soldering pad after removing the power supply chipset Pic 1-1
Continuing to eliminate the short circuit of other parts, after we disconnected the power supply of U5411_RF (As shown in Pic 1-2), the ground impedance values of voltage PP1V8_SDRAM was normal.
The position of U5411_RF on the motherboard Pic 1-2
After removing the CPU (As shown in Pic 1-3), the ground impedance values of voltage PP1V2_SDRAM was normal. But since this voltage was the power supply to CPU and temporary storage, so we still not sure if it was the damage of CPU or temporary storage, we could only repair by eliminating.
The CPU soldering pad Pic 1-3
The disassembled CPU has slight copper dew, coating the exposed copper position with the green oil and replanting the ball. The CPU after finishing the ball planting is shown in Pic 1-4.
The CPU after finishing the ball planting Pic 1-4
After soldering the CPU, we could sure that the fault was caused by temporary storage because the motherboard could be powered on. After replacing with a good temporary storage, the phone could be started up. This problem solved.
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