How to fix iPhone 6S half black screen

Fault Description: iPhone 6S half black screen happens 

According to we ever known, it is a great possibility for most of phenomenon to suffer the phone motherboard.

So we decided to disassemble the iPhone 6S motherboard, and check the corresponding current.

After receiving the board, we are going to install to test it first,  the right screen is not bright as the left side, so the iPhone 6S screen fault is confirmed now.

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First check the display base J4200, we didn't find any problem from the appearance.

When the resistance to the ground is measured by a Fluke digital multimeter, the resistance values of 1# and 3# are the same, and there is a connection between 1# and 3# by measuring, it is judged that there is a tin link between the two pin.

Clean the black glue around the base, tin ball is seen between the two circuit, leading to the two circuit connecting. This is the main cause of the failure of half black screen.

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At last, gently remove the tin ball and install the iPhone 6S motherboard to test.

The half black screen failure is solved now. All other functions tested are also OK.

Solutions for iPhone 6S no ringtone

Fault Description: iPhone 6S happens ringtone function faults.

Actually, we will be habit to check the control IC customarily, following the details step by step:

First of all, we install the iPhone 6S motherboard to test whether there is any vibration without bell, because ringing and vibration are closely related. 

It is found that the vibrating bell is not entirely absent, there a little sound just click it, then the sound disappeared at soon.

For this kind of situation, we can give priority to check the iPhone 6S bell boost in this respect, observe under the LED Stereo microscope, we found the L3700 bell boost a little blackened.

The picture are shown as as follows:

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Solution: 

Replace a new L3700 coil, install the iPhone to test again, the ringtone fault is perfect solved now! (general coil without direction and model difference, can be commonly used)

After that, we advise you guys had better use it carefully 

Solutions for iPad Mini2 No Backlight and No Display

After we got the iPad Mini 2, we disassemble it without any doubt, cuz there absolutely no display and no any backlight, the key is that it was dropped into water.

Get the motherboard, and separating it from the shell, we need to check the power current firstly. After that, we start our observation. 

Open the iPad Mini 2 to observe, we can see that the lower half of the motherboard is water damaged. Check the motherboard under the magnifying glass carefully. The power supply and the display interface are corroded badly.

First we deal with the power part, and then carefully deal with the display interface, because this iPad is the display and backlight problem, when finished processing, one of the resistors fell down, check the schematic diagram on WUXINJI dongle, we found it's the light IO data interface, this resistance is 1 ohm.

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The ground resistance value was measured by Fluke digital multimeter at the display interface after the short connection with jumper wire. It was found that there were four places where the resistance value of the pin have no resistance value.

Short connect one by one, it has display but no backlight, so we concentrate on the high voltage side  at this time, we found that the backlight positive pole and the interface are corrosive under the microscope,  so we slowly scrape with a knife, and then weld with 0.01mm Jumper Wire, to prevent loose weld when install the display screen.

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Install to test, the problem is solved now.

Solutions for iPhone 6S not charging problem

After we got that, according to its master describing, we know that it was dropped into water and can't be restarted.

Check it with DC power supply, there happens abnormal value and we need to disassemble it.

Use Stereo Zoom Microscope to observe the iPhone charge circuit, there are no visible signs of water damage on iPhone tail plugs.

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Considering that the upper part of the iPhone motherboard has water damage，and the iPhone can be connected to the computer, according to the previously repair experience, we should focus on the water damage circuit of the iPhone motherboard. Check it carefully, we find the resistor R4510 is corroded by water.

After check iPhone 6S schematic diagram on WUXINJI Dongle, we know that this circuit for iPhone main power that output to the USB control signal TRistat_USB.

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Now, we found the faulty part, so, clean the corroded area and replace the resistor by using QUICK 861DW hot air rework station and Titanium Alloy Tweezers.

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Install the iPhone and test it, all functions works normally.

Solutions for iPhone 6S Turn On Failure

Checking and observing, we got the faults. The phone motherboard happens short circuit after being dropped into water.

And then, we disassemble it, and find that the power supply IC is corroded, so we may need to check the current carefully.

After cleaning the corroded part, it still won't turn on. The leakage is 6 Ma and the starting current is 50 ma by measuring with DC power supply.

Due to the fact that IC is more likely to cause this failure, we are going to remove it to retest, the problem is solved now. Then replace the display IC and install to test function.

All functions are normal, but it can not charge and also can not connect to the computer now, after replacing U2 u2300, fault still exists, then remove the shield cover, measuring its IC side circuit, we found that the end of the capacitor c2300 corrosion blackened.

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After checking the drawings on WUXINJI dongle, the capacitor can not be removed because it is not a ground protection capacitor, but a coupling capacitor on the TIGRIS-BOOT circuit.

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Finally, directly replace an old iPhone 6s motherboard with a good capacitor and replace it again, the problem is finally solved now.

Solutions for iPhone 7 water damaged

While the next phone occurred water damaged faults,  it can't be restarted,  we connect it with the DC power supply to check the iPhone status.  Most of this case was caused by short circuit.

Anyway, we still need to check the exterior of the iPhone, this part is much weak after being dropped into water.

Connect iPhone motherboard to DC Power supply, no leakage, press the iPhone power button, the current jumps from 200 mA, this failure mostly is caused by power supply short circuit, it also can be measured, just check the several power supply circuits that is output by the main power supply.

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After measuring these power supply circuits, we can identify where the short circuit part is.

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When measured the PP3V0_TRISTAR_ANT_PROX this signal, we found it is short circuit. This signal is reached to these place and USB, we can check it on iPhone 7 schematic diagram.

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Directly remove the USB, and then measure the iPhone data again, but the iPhone still short circuit.  For water damaged iPhone, we need to observe iPhone exterior more carefully, and the customer has been repaired this iPhone before, put iPhone motherboard under the Trinocular Stereo Microscope and then continue to observe it.

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We found there is a damaged chip, it's probably the damaged chip that caused the PP3V0_TRISTAR_ANT_PROX to short-circuit. Remove the inductance attached to it， after remove this inductance, we found the resistance value of PP3V0_TRISTAR_ANT_PROX is back to normal. Now, install the USB.

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Press the iPhone power button, now it is normal, but the iPhone always stuck on white Apple logo and won't enter the IOS system. The current tested by DC power supply is to 2A and then down to 200mA and then stop, we suspect it is caused by iPhone audio problem, the current is normal, but it down to 200mA and won't move.  

After detected, there's damage on both sides of the audio, use QUICK 861DW hot air rework station to remove the iPhone audio IC and replace the new one. Test it again, now the iPhone can be entered the iOS system quickly. The repairs end!

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Solutions for iPhone 6S retains signal under without SIM card

Fault Description: iPhone 6S retains signal after being removed SIM card

According to our ever experience, there may exist there following issues:

- Abnormal card holder

- Card detection pin problem

- Baseband Signal part problem

But we need to confirm it on this phone, let us start it.

Install the iPhone to test, we found that as the customer said, there is still a signal even if the SIM card was pulled out. According to previous maintenance experience, first we use FLUKE digital multimeter to check the resistance of each pin of the card base, especially the resistance of the card detection pin (that is, the card switch).

After measuring, it is found that the card detection pin has no resistance value. At the other end of the R3401, the resistance can be measured, and the fault is determined in the card detection pin, which is broken.

Solution: you can use jumper wire to connect directly to the card detection pin without removing the card holder.

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Connect R3401 to the eighth pin of J3001.

The operation is shown under Trinocular Stereo Microscope as the following pictures:

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After that, we reinstall it, test it and check it again, without SIM card, without signal, it is a normal one.

Solutions for iPhone 6P no display no backlight problems

While we got the iPhone 6P, the emails describes it can't work normal, doesn't display and no backlight.

Though we found there no obviously damage outside,  it still don't like a new one. Its master said the iPhone 6P  was repaired once, so we decided to disassemble it and found the faults.

Use phone opening tools to disassemble the iPhone, take out the iPhone motherboard. Put iPhone motherboard under the Trinocular Stereo Microscope to observe, we found the iPhone display touch IC of the iPhone motherboard, iPhone light control IC U1501 and NUT column all have been removed. Moreover, the bottom of the NUT column on the iPhone motherboard has been hit by a long screw.  

Use QUICK 861DW hot air rework station and BGA remove graver to scrape it, there is no disconnection phenomenon.

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Measuring the resistance value for the D3# layer of the iPhone display touch power supply IC U1501 by digital multimeter, there is no resistance, which is abnormal.

After check iPhone schematic diagram on the WUXINJI Dongle, we use QUICK 861DW hot air rework station to solder a jump wire from resistor R0302 to U1501D3#, and then install a good U1501.

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After installation, measure the iPhone 6P again, now the data tested is normal.

Install the iPhone, and turn on iPhone to test, the iPhone displays properly, other functions tested also are normal, the fault has been repaired!