ipad Air 2 boot into system Red screen reboot
Other maintenance man sent it and said: it cannot be charged, but after replace the USB management chip, the charging went back normal. However, after assembling it, he found that it sometimes can get into IOS and sometimes screen turns red and roots itself.
Repair Process
As other maintenance man have replaced USB management chip, I worry about that the USB management chip is damaged or the solder is worse, so I replace the chip again. But the problem remains the same, which suggests that USB management chip is workable.
Next I use the smallest peripherals method to exclude the faulty places. Unplug all the connection cable from other peripherals to motherboard, such as camera, sensitization, as shown in picture 7-14.
Picture 7-14
Put the single motherboard with display flex cable on electric tester. After unplugging all peripherals and testing many times, the problem remains the same, which suggests that the problem is unrelated with peripherals.
Judging from my repair experience, after excluding the peripherals problems, damaged NAND FLASH and pseudo soldering could cause iPad red screen.
Problems are sure to happen at CPU and NAND FLASH. Next, we have to think whether to fix CPU or replace NAND FLASH. Under the rule of taking the easiest the first, I replace the NAND FLASH. The motherboard without NAND FLASH is shown in picture 7-15.
Picture 7-15
But after soldering NAND FLASH again, the problem remains the same. Now the problem is left to CPU. Re-solder CPU and test. The problem disappear.
When assembling iPad, I find new dropping marks, so I guess that the iPad has been dropped, which causes CPU damage. When other maintenance man was tearing USB management chip, the motherboard was heated and the damaged CPU is pseudo soldering.
Repair Process
As other maintenance man have replaced USB management chip, I worry about that the USB management chip is damaged or the solder is worse, so I replace the chip again. But the problem remains the same, which suggests that USB management chip is workable.
Next I use the smallest peripherals method to exclude the faulty places. Unplug all the connection cable from other peripherals to motherboard, such as camera, sensitization, as shown in picture 7-14.
Picture 7-14
Put the single motherboard with display flex cable on electric tester. After unplugging all peripherals and testing many times, the problem remains the same, which suggests that the problem is unrelated with peripherals.
Judging from my repair experience, after excluding the peripherals problems, damaged NAND FLASH and pseudo soldering could cause iPad red screen.
Problems are sure to happen at CPU and NAND FLASH. Next, we have to think whether to fix CPU or replace NAND FLASH. Under the rule of taking the easiest the first, I replace the NAND FLASH. The motherboard without NAND FLASH is shown in picture 7-15.
Picture 7-15
But after soldering NAND FLASH again, the problem remains the same. Now the problem is left to CPU. Re-solder CPU and test. The problem disappear.
When assembling iPad, I find new dropping marks, so I guess that the iPad has been dropped, which causes CPU damage. When other maintenance man was tearing USB management chip, the motherboard was heated and the damaged CPU is pseudo soldering.
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