Professional Way for Repair iPad Air 2 Turn On failure

Most of repair way on Apple device are similar,  such as iPad Air 2 with iPhone 7.

First step we need to check is enter the DFU mode to check the sources faults, then decide what we should do next.

while connecting the iPad with computer to see if it is in the mode. If we can enter the mode, then it should be judged by reflash.

After connection, the computer was found in the recovery mode, but there is no serial number , it seems that the NAND flash chip is not recognized. In general, there were two kinds of faults: one is the NAND chip and the other is the circuit which connect the CPU and Nand is broken.

This is easier to deal with, remove the iPad Air2 NAND chip, nothing is abnormal when we use Fluke digital multimeter to measure the grounding resistance of the NAND pad, that we judge it may be the problem of the NAND chip. Remove the NAND chip off and put it on iPad NAND Test Fixture, it can't be read so we can judge that the NAND chip has problem. Replace the NAND chip and write a set of serial number code without ID on the test fixture, then weld the NAND chip back to the motherboard with QUICK 861DW Hot Air Station.

Reinstall the iPad to reflash, the NAND chip can finally be recognized now, also the progress bar works well!

The recovery process passes normally, and all the functions are tested well, repair ends here.

Summary: This reboot failure is caused by the damage of the iPad Air2 NAND flash chip.

 Then, we can clear see the results, sometimes booting failure always along with the NAND flash chip, so we may focus on this problem, which may be useful for the future's diagnostic.

Repair iPhone 6S stuck on white apple logo

After receiving the iPhone 6S, we got through a call with our customer, then we know what happens.

We reboot it, enter the DFU mode which can be online, so we ensure it has nothing to do with U2 fault

While there is automatic black screen after the white apple appears. The computer prompt can not jump from DFU to recovery mode. This is often caused by iPhone NAND or CPU.

The power supply of the iPhone 6s can be measured according to the WUXINJI schematic diagram. The two 1.8V are on C1534 and C1560 respectively, 0.9V is on C1548, and 3.0V is on C1502, and the NAND voltage is normal. You need to take down the pin resistance of the NAND to see if there is a break between the CPU and the NAND chip.

At the same time, you need to test whether the NAND itself is damaged. The protective measures should be pre heated to remove glue, and the temperature is about 220 degrees. Choose the thinnest blade, except for the right side of the adhesive, there must be some small resistance around it. If it falls, it must be filled.

The QUICK 861DW hot air gun can be selected to remove the NAND chip, and the heat transfer area is large, the temperature should be set about 350 degrees. When heated to a certain extent, you can tentatively take the thin slices and insert them into the hard disk. When the tin starts melting, you can pick them up. Do not use great force to avoid dropping the NAND and pads. (temperature is related to equipment and personal techniques).

        

  

After testing, the NAND pin is normal, take the WL PCIE programmer(VC748) to read the data.

   

NAND data is displayed normal, remove broken line and NAND problem, reinstall the NAND to reflash the iPhone, all the function is normal now!