Repair Guide: iPhone 7 Plus Backlight Failure

Check iPhone schematic diagram on WUXINJI Dongle, we know that there are two sets of backlights, one set is on the left of the iPhone display screen, and one set is one the right of the iPhone screen, they are controlled by light boost IC-- A and light boost IC-- B.

The light boost IC--A controls the backlight on the right side of the screen, it controlled by three sets of signals: PP_LCM_BL_ANODE (10.5V cathode power supply),PP_LCM_BL_CAT1 and PP_LCM_BL_CAT2. If these three sets of signals don't work or the light boost IC-- A damage will cause iPhone right screen won't light.

The light boost IC--A external two sets of diodes and boost inductors, the iPhone 6 only have one set, and because the iPhone 6S has one more function, the iPhone front camera comes with flashlight, so this front flash light is provided by the newly added set of rectifier diodes and boost inductors. If one of these is damaged, then it will cause boost light IC--B was burned, you have to replace it.

The light boost IC--B controls the backlight on the left side of the iPhone display screen, it controlled by three sets of signals: PP_LCAM_BL34_ANODE(10.5V cathode power supply), PP_LCM_BL_CAT3 and PP_LCM_BL_CAT4. If these three sets of signals don't work or the light boost IC-- B damage will cause iPhone left screen won't lit.

The light boost IC-- B external two sets of diodes and boost inductors, the iPhone 6 only has one set. Because iPhone 6S has one more function, its front camera comes with flash light, and it is provided by the newly added set of rectifier diodes and boost inductors. So, if one of them is damaged, it will cause boost light IC--B was burned, you have to replace it by using QUICK 861DW and Precision Titanium Alloy Tweezers.

The boost inductance of the lighting part is integrated in an IC (Inductive integrated IC)， this IC integrates the inductance for lighting part, the display part, the charging part and the ring-tone part. The damaged inductive integrated IC will cause iPhone no backlight no display issues, and will cause iPhone no charge, no ringtone and no vibration failures.

Excellent Solution: iPhone 6 Plus black screen issue

The iPhone 6 Plus is turned on, it shows black screen, the iPhone screen has no display. What's trouble? Here to get excellent solution. 

Put iPhone under the WL Aluminum Alloy Pad, and then replace the new iPhone display screen to test, it still shows black screen. Now, we can confirm that it's not iPhone screen problem, we need to check iPhone motherboard.

Tear down the iPhone motherboard, and then remove the iPhone motherboard. Frist measure the iPhone iPhone power supply with Fluke 15B+digital multimeter, nothing issues was found. 

Assemble the iPhone display IC, and then measure it, the boot current jumps abnormally.
We can see the backlight behind the screen is bright, the measurement of +5.7V power supply is only about 2.2V, -5.7V has no voltage. 

Now, we estimate the iPhone display IC internal boost exists problem, and the WUXINJI dongle circuit diagram shows that the capacitor C1554 energy storage booster capacitor is short circuited.

Use QUICK 861DW hot air rework staiton to remove the damaged capacitor, and then install the good capatitor to it.  Now, measure it agian, the data jumps normally.

Install the iPhone to test, now the iPhone screen works perfectly.

Solved: iPhone 7 stuck on Apple Logo won’t boot issue

After use iTunes to update the IOS on iPhone 7, the iPhone cannot be turn on anymore, it just stuck on Apple logo. How to solve it?

Disassemble the iPhone 7 by phone opening tools, and then measure the iPhone motherboard by DC power supply, the power scurrent stop at around 150mA.  Touch the iPhone home button, it has response, and the flash can be finished normally, which means that the iPhone booting condition is normal.

Remove all iPhone external accessories, and then test it again, the result is the same.

Press the iPhone power button, after a while, it gets into interface, but the iPhone still runs slowly, and we found that if we clicking on the file or interface related to the sound, the iPhone will get stuck and stop running. As we know, the iPhone 7 audio IC is easy to damage, so we decided to take out the U1301 big audio to check.

Before we take out the iPhone audio IC by using QUICK 861DW hot air rework station, we need to protect the other ICs next to it ( below it is iPhone Nand flash, above is a iPhone large power IC, on the back is the iPhone baseband CPU)

After remove the iPhone big audio IC, we found the problem on the solder pad. The solder joints of the two pins of the chip C12 and J12 have been lost. Observe it under the 7-45X Trinocular Stereo Microscope, finding that the jump wire between C12 and J12 is easy to disconnect. Check iPhone schematic diagram on WUXINJI Dongle, there are 2 capacitors next to this audio, there are two resistors next to the audio lead to these two points respectively.

Welding jump wire to these two points respectively, the probability of C12 disconnection is relatively large. it is a signal that the CPU gives to audio. The iPhone big audio IC doesn't need to replace the new one, just re-weld tin to old one.

Install the iPhone, and press the iPhone power button, now the iPhone 7 can be turn on smoothly, the problem has been solved！

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.

iPhone 7 Plus Shows iTunes Error 56—How to fix?

The iPhone 7 Plus accidentally fell into water while in the normal use, even we pick it up and dry it quickly, it still has many problems, such as iTunes error 56.

When we connect iPhone 7 Plus to computer with iPhone lightning cable, and the opne the iTunes on PC, we are going to flash iPhone by iTunes.  It started smoothly, but when the flash process bar runs
to two-thirds, it stop runs and the iTunes reports unknown error 56.

As we know, iTunes error 56 mostly is caused by iPhone baseband circuit and NFC. Now, we need to find out the reason, and then we can fix it.

Use phone opening tools to disassemble the iPhone,  take out the iPhone motherboard to check , no obvious scar.

Measure the iPhone baseband circuit part, no problems was found. Now, put iPhone motherboard under the Phone Repair 7-45X Trinocular Stereo Microscope to observe, finding that the NFCSW_RF power supply tube is seriously corroded.

Carefully handle the eroded pin well, and then solder it well by PPD 861D Plus hot air rework station. 

Assemble the iPhone, and use iTunes flash it again, it works good, and final get into IOS.