IPhone 8 won’t turn on  

The following describes the repair sequence for iPhone 8 when the phone won’t turn on.

First, we disassembled the phone, removed the motherboard.

Then we performed a visual examination of the board under a microscope, for the presence of:

• traces of moisture,
• soldering traces (flux residues, solder balls on the board),
• mechanical damage on the board,
• the presence of protective screens.

Using a multimeter, in ohmmeter mode, we measured the power supply circuit of the iPhone 8 (U2600) memory to match the resistance to the operating values.

Namely:

• PP3V0_NAND

• PP1V8_IO

• PP0V9_NAND

• The resistances of the U2600 power circuits corresponded to the resistances in the power circuits of a knownly good iPhone 8 board. The next step in diagnostics is to measure the voltages in the above circuits.The voltage in the lines corresponded to the voltages indicated in the circuit description.Making a conclusion on the basis of the diagnostics already carried out, we understand that the phone memory is faulty, since there is no short circuit on the flash drive’s power lines, and there are operating voltages.After disassembling the memory of iPhone 8, we cleaned the remains of the compound, washed off the remains of the flux. Then we measured the resistance on the contact pad of the U2600 chip.

• As a result of the measurements, it turned out that there were no breaks in the board. From this we conclude that the U2600 chip is faulty. To replace the memory, an iPhone X board with 256 GB of memory was used, since the memory chips are interchangeable.
  How was the iPhone X memory removed:
  • We fixed the iPhone X board into the termopro CTM 10-6 circuit board heater.

• Split the board of the iPhone X.

• Using the JC Pro 1000S programmer, we read information (serial number, MAC addresses of Wi-Fi and Bluetooth, etc.) and recorded it in the memory from iPhone X. Next, we made a memory reball and soldered it to the iPhone 8 contact pad, using the key.The next required step is to check the board for a short circuit. When checking short circuit was not found.Then we put the board in the phone case.

• We cleaned the compound and dismantled the memory.

• We flashed the device using iTunes. After that, the iPhone 8 was successfully activated.