A customer brought their iPad in because it would not start up. This seems to be a common problem with many iPads, in the trade we call it ‘Boot Loop’. There are several reasons for this to happen:
- Faulty battery
- The main processor or NAND has lifted from the board
- Corrupted iOS
All the iPad would do is show an Apple logo, then go dark, and repeat. Because this is the same way a device with software corruption will present, our first step was to try an iTunes update, or restore. The iPad 7 would fail iTunes update with a general error 4013. iTunes Error 4013 means “I don’t feel good, something is wrong” It gave us little to go on.
We opened the iPad. There was no water damage or any physical signs of problems. The logic board could not boot even in a known good housing with a good battery. It was inexplicably brain dead. The CPU could not function and we didn’t know why.
Time went by and another iPad 7 showed up with the same symptoms. Apple logo boot loop, error 4013. This time we found a clue. The tristar tester tool revealed that the charge port had been damaged, as well as a usb permission chip on the logic board. However, even after fixing those problems, the CPU still would not function.
On this iPad, data was important. The owner of this iPad would have lost much of her life’s work if we could not recover the data on the iPad by getting it to boot.
In desperation, we tried transferring the CPU and NAND to a receiver board. We doubted it would change things–if the CPU was dead it would have been electrically killed. Without any physical damage there was no way the CPU was simply “detached” Surprisingly, the iPad booted up after the extensive CPU transplant surgery. All of the data was recovered.
Since then, we’ve seen this case many times. Using aftermarket chargers will sometimes affect the CPU itself, beyond the typical damage that we often see to the charger-facing circuitry. When this happens, the CPU can not function and will cause the device to show Apple logo boot loop and fail iTunes update with error 4013.
We no longer need to transfer the CPU to our known good receiver board, we have learned that removing the delicate CPU, cleaning the hard electrical superglue “underfill” from both the chip and board, then resoldering new conductive balls to the chip and attaching it back in its original position will bring these iPad 7’s back to life.
While this seems to be a unique susceptibility of the iPad 7 A10 CPU and the associated iPad charging system, we wondered if this same fault could occur in other devices. The closest match is the iPhone 7 which also uses the same A10 CPU as the iPad 7. We found a perplexing case of iPhone 7 Apple logo boot loop, with error 4013 on update. Sure enough, removing the CPU and reinstalling it brought the iPhone 7 back to life. We were able to recover all the data.