Replacing NAND Flash in Bgacenter
In the next step, we carefully examined the board under a microscope. The results of the inspection are as follows:
Then we soldered the protective shield on the back side of the board (side B) using the lower heating TERMOPRO.
Testing with a multimeter in diode mode
Using a multimeter in diode test mode, we checked the U4 power supply circuit for a short circuit. The measurements were carried out on capacitors installed in the power lines PP3V0_NAND and PP1V8.
No short circuit was detected in the tested lines.
It was decided to replace NAND Flash (U4 chip)
To repair 5S with error 4013 and replace U4, we fixed the board into the board heater.
￼We cleaned the compound around the chip. Pay attention to the cleaning of the compound next to the U23 backlight chip. It has a glass case and is very fragile.
We soldered a U4 with a hot air soldering station. Then we collected the remains of solder on the contact pad with a braid and cleaned the compound. Then we checked the connection with U1 – the central processing unit (CPU) for breaks. The connection between U1 and U4 is not broken. Using a soldering iron and a braid, we prepared the contacts of the soldered chip. IP Box 2 checked the removed NAND Flash for the presence of bad blocks (bad sectors). There were a large number of them, it was decided to replace U4 with another.
To verify that the CPU is not damaged by temperature, we flashed the 5S board without NAND, got error 9 (in iOS 11 this error was 40) It means that there is no drive on the board.
We recorded information from the “old” NAND and saved it in a text document for further recording in the newly installed NAND Flash.
Then we took the following steps:
Error 4013 on iPhone 5s most often indicates a malfunctioning phone memory. In the Bgacenter training center, as part of the training course, you will be shown and taught how to repair such malfunctions.