Solved: iPhone 6 won’t boot after LCD screen replacement

 The iPhone 6 LCD screen has some problem, so we replace it and then we try to turn on iPhone to test, after we press the iPhone power button, the iPhone 6 won't boot, it just stuck on white Apple logo and then auto restart.  We need to solved it.

  

According to repair experience, we need to check iPhone CPU part. Check the bus and reset first, both of them are normal. Cut the shiled cover above the fingerprint, use Fluke 15B+ digital multimeter to measure the resistance of CPU to the clock and data.

The normal values of R0317 and R0316 are more than 400, the measurement of R0317 resistance is 745, and the R0316 is 479. This case is mostly the two pin of AP31 and AR31 in the right lower right corner of CPU has pseudo soldering. First press the iPhone 6 CPU to test whether the device can turn on or not, do not try to reflash the phone first, it will report error 9. Of course, the best method for CPU pseudo soldering is redo the parts, here we try a method of jumper wire connection without removing CPU necessary (6 and 6P can be common used).

As shown in picture 17-1-1, look at the position of the two points on the wuxinji schematic diagram, the lower right corner is 0, the width is 1.45MM (the width of 4 solder joints), the height is 1.75MM (the height of the 7 solder joints), which can be slightly shaved on this basis, first probably draw a rectangle. When the upper cover is very hard, do not use brute force, select a sharp phone repair blade, you should slow down when finish scraping on the white pad from cover to the CPU upper cover, after scraping the white pad, the point we are looking for will come out, the wire on the CPU chip must be operated under the HDMI Camera microscope.

First test the resistance of the two points. If normal, smear green oil on the top (except for the two points we are going to connect jumper wire). After the curing we can connect jumper wire, use QUICK TR1300A hot air gun to blow very small tin balls on the 2 points respectively , we choose to use the wire of the receiver, it's thinner, the receiver wire is with glue, scrape the 2 ends and apply a little solder. As shown in picture 17-1-2.

Use jumper wire on the corresponding two points separately. ( it's better to do on both two points to avoid rework repair). Once you finish flying, just apply the green oil and use 5V USB Ultra Violet Light Lamp for curing.

Now, meausre the iPhone 6 agian, the data is normal. Install the iPhone,and press the iPhone power button, now the iPhone 6 can be turned on smoothly. 

Detailed Solution for iPhone 6 won't boot after dropped into water (short-circuit)

If the iPhone dropped into water, then you must have the idea that the iPhone motherboard is damaged.  Moreover, the iPhone won't boot. After water damaged, the most common phenomenon is the short circuit on the motherboard, and there has two cases. Let's take iPhone 6 won't boot after dropped into water as the  an example.

 

The water damaged the iPhone 6, now the problem is that the iPhone 6 won't boot.

First of all, we need to disassemble the iPhone, take off the iPhone motherboard, and then measure it with DC power supply.

Case 1

When supply power to measure the iPhone motherboard, there is large current alerts on DC power supply display screen, which means that there is a leakage phenomenon. Generally, when powering the motherboard and then it shows power leakage issue, the Rosin method is the best choice.

Use Fluke 15B+Digital Multimeter to measure the diode data for iPhone battery interface positive, the data is normal. Continue to measure the diode data for main power supply VCC_MAIN circuit, finding that the diode data for this circuit line is too small, which means that there is a short circuit here.

Smoke the iPhone motherboard to white with rosin, add voltage on VCC_MAIN, after for a while, we found a capacitor is shorted.

With the help of QUICK 861DW rework station and tweezers, we remove it smoothly and quickly. After remove that capacitor, measure it again, the data is normal now.

Install the iPhone to test, the iPhone 6 can be turned on smoothly.

Case 2

When the iPhone motherboard is being measured by powering, it won't leak, but when we press the iPhone power button, the current stuck on 200mA. Obviously, a load on the iPhone power IC is short-circuited.

Use multimeter to measure the resistance of each output grounded on the iPhone power IC, when the PP1V8_SDRAM circuit is measured, we found the problem, the PP1V8_SDRAM circuit is shorted, because the data for C1243 is too small.

Put iPhone motherboard under the Phone Repair 7-45X Trinocular Stereo Microscope, and then apply some rosin on motherboard, and then use Quick 861DW hot air rework station to smoke it, till the motherboard turns white.  Increase the voltage in the C1243, after a while, we found a capacitor is shorted.

Remove this capacitor as usual, and then measure it again, now the data is normal.

Assemble the iPhone to test; now the iPhone 6 can be turned on smoothly. After get into IOS, test all function on iPhone, everything works well.

DIY FIX: Backlight damage causes iPhone 6 won't boot

 Today, we will share a iPhone repair guide that how to DIY fix backlight damage causes iPhone 6 won't boot. When we supply power to iPhone 6 with C48 MFI USB Cable, the iPhone always shows black screen. Let's learn to diy fix it!

Connect iPhone to DC power supply, we find current 80mA circularly run while connecting and triggering, so maybe it's USB damgage cause I2C short circuit during charging process, first remove the iPhone 6 motherboard and take the USB off, but it's still the same as before, then we measure the I2C resistance and power supply! It is found that the I2C 0SCL is in a short circuit state. As shown in picture 11-10-1.

Since it's short circuit, it means the connected chip is damaged, the connected chips have display, backlight, main power supply USB and the iPhone 6 CPU.

First observe with VGA Camera 7-45X Trinocular Stereo Microscope, it is found that all the backlight diodes are burning and discoloring.

Then remove the backlight first, it does not short-circuit. The trigger current is normal, so continue to replace the 3 piece of iPhone backlight chips.

According to our past experience, if the large inductors gets discoloring, the large inductors with connected iPhone backlight IC would also have problems, so we replace them together. As shown in picture 11-10-2.

Measure it again with DC power supply, now the current is back to normal.  At last, instal the USB, and turn on iPhone, it runs smoothly and successfully. Keep going to check other functions, all is fine. The repairs end!