Solution: Drop-damaged iPhone 6S Plus poor WIFI signal

 Here is an drop-damaged iPhone 6S Plus with poor WIFI signal problem, we need a solution for this problem. 

Trouble phenomenon

This iPhone 6S Plus accidentally fell into the ground, luckily the iPhone 6SP still can turn on, but unfortunately we found the iPhone WIFI signal is abnormal, the signal is very poor, which causes iPhone WIFI function can't  used normally.

Solution

First, disassemble the iPhone 6SP by phone opening tools, open the iPhone display assembly, take out the iPhone motherboard. 

Now, we need to check iPhone WIFI IC, so fix iPhone motherboard by PCB holder fixture, use QUICK 861DW hot air rework station to heat the iPhone WIFI IC, and then use tweezers to remove the iPhone WIFI IC.

Observe it under the microscope, we found there are many pin are missing, and most of them are useful pins.

Because replace iPhone 6S WIFI need to unbound the WIFI on the iPhone Nand flash, otherwise, the iPhone WIFI function can't be used.

Now, remove the iPhone Nand flash, and then put iPhone Nand flash on the JC Pro1000S chip programmer to unbound the WIFI, and then re-install the iPhone Nand flash.

After handling the iPhone Nand flash, we are starting to handle the solder pad, solder the jumper wire and fill the missing pins, re-fill all of the useful pins, and then install the new iPhone WIFI IC. 

Measuring the data of iPhone motherboard, all data tested are normal. Install the iPhone 6S Plus and turn it on, after entering the IOS system, test the iPhone WIFI function, now it works properly. 

Troubleshoot: iPhone 6S receiver failure (no voice)

Last week, we received an iPhone 6S need to repair, the problem is that the iPhone receiver is failed to work,  the iPhone 6S receiver has no voice when calling. After testing, the iPhone receiver is not working, but the iPhone speaker works good. Now, we need to troubleshoot it.

There are several reasons will cause iPhone receiver failure:

 
- iPhone receiver, 
- Receiver flex cable
- Receiver circuit 
- iPhone audio IC problem

How to troubleshoot? 

First , replace the receiver and flex cable, and then test the iPhone 6S, but the failure still exist.

Use digital multimeter to measure the diode data of receiver signal 1 pin and 3 pin that on the connector J3100, the data measured are normal.

Check iPhone schematic diagram via WUXINJI Dongle, we know that the 1 pin and 3 pin of J3100 are through capacitor FL3153 and FL3154 to iPhone audio IC U3500, their diode data are normal, which means the capacitor FL3153 and FL3154 are normal.

After excluding the cause of the peripheral components，we start to check U3500. Take out the iPhone motherboard, we found the U3500 has been replaced before by other repair man,  the several filter capacitors around it has been removed, and there is a power supply IC of NFC also has been removed.

Now, we need to fix iPhone receiver failure, directly replace the iPhone audio IC U3500. After replacement, connect iPhone 6S to the DC power supply, the trigger current jumps from 0 to 80mA, it's been circulating like this.

The replacement IC has been soldered well, the iPhone CPU didn't been blown by QUICK 861DW hot air rework station. Remove the iPhone audio IC, now the current is back to normal, so we confirmed that it's the problem of the iPhone audio IC. Replace it with new iPhone audio IC,now the data tested is normal.

Finally, assemble the iPhone 6S, power on iPhone, entering the IOS,  and then test the iPhone receiver, now the iPhone receiver is working properly. The tourble has been fixed!

Solved: iPhone 6S failed to boot after water damaged

A customer sent us an iPhone 6S to repair, the problem is that iPhone 6S failed to boot after water damaged, and this iPhone 6S was repaired by other repair man, but still not turning on, he want us can help him to solve this problem.

After we received the iPhone 6S,  first dissemble iphone with iPhone opening tool  , we saw that the motherboard was flooded with water, we cleaned the water area thoroughly, it seems that CPU Upper also exist fault. After tested resistance and powered on, there is no short circuit. Connect the iphone motherboard to the DPS DC power supply, we find the current value is about 240MA.

Test PP-VCC-MIAN with a digital multimeter , exist phenomenon of short circuit, the resistance is small, only dozens of ohms. Observe carefully, we found that capacitor next to the WIFI chip was black seriously.

Use QUICK 861DW Hot Air Station  to remove the capacitor,  resistance is tested more than 100 ohms, and the current measured is also more than 100 mA. Due to the large water poured area, it was found that a capacitor on the iPhone audio IC  also became black seriously, we can check iPhone schematic diagram via WUXINJI Dongle.

 

After removing the capacitor, measure PP-VCC-MIAN, then insert the DC power supply  again, the current become more than 30 mA. Test multiple power supply, there is no short circuit, connect to the power supply, we feel a slight heat. So fumigate rosin in the upper part. It was found that power supply portion was hotter than other parts. After removing the display power, the current returns to normal.

Remove the iPhone power IC, test the iPhone motherboard again, now all data tested are normal.

Assemble the iPhone, press the iPhone power button, the iPhone 6S can be turned on successfully now. After entering the IOS, test all functions on iPhone 6S, all works well, the problem has been solved!

iPhone 6 Compass Unable To Use- How To Fix?

The iPhone 6 compass unable to use, and it causes iPhone overheat and fast comsumption, how to fix it? 

Disassemble the iPhone by phone opening tools, and test the iPhone with DC power supply, the iPhone 6 can be turned on, and it's going to IOS system smoothly. Test it in the black screen status, the working current is always around 250mA, this is obviously abnormal. 

Enter the IOS, and test the iPhone functions, 3D touch is normal, iPhone camera is normal, the speaker is normal, when test the iPhone compass function, we found the iPhone compass function doesn't work, it can't be used. 

Carefully take out iPhone motherboard, and then measure the diode data of the compass IC power supply by digital multimeter, finding that PP3V0_IMU is short-circuited. 

Compared with iPhone schematic diagram via ZXW Dongle, finding that there are some filter capacitors on the circuit line of the PP3V0_IMU voltage. 

In order to find out the real fauly capacitor, we need to remove those capacitor one-by-one. Put iPhone motherboard under the microscope, after remove the C1902 capacitor, we found the PP3V0_IMU voltage is back to normal. 

Find a new C1902 capacitor, and then install it to the iPhone motherboard. After replacement, measure the iPhone standby current again by DC power supply,now the data tested is normal. 

Assemble the iPhone, and test the iPhone compass function in the IOS system, it works perfectly. The iPhone 6 has been fixed!

iPhone 6 Plus touch screen not working- how to fix?

The iPhone 6 Plus touch is not working, becuase it doesn't response to the touch, how to fix it? 

First, we try to fix it by replacing iPhone touch screen. Use phone open tools to disassemble the iPhone, remove the iPhone display assembly, and then install the new iPhone display assembly. After replacement, power on iPhone and test the iPhone touch screen, it's still not working.

Now, we need to check iPhone motherboard. The bottom of the UMT board is easy to disconnect, first we need to handle the iPhone touch error. There are 2 ways to remove the IC: one is remove it by tweezers; the other one is pry it from the side the IC.

Remove the iPhone touch IC and the re-install it, the iPhone 6 Plus auto restarts when the white Apple appears. Measure the iPhone by DC power supply, the boot current jumps from 300mA.

Take off the iPhone touch IC again to measure the resistance of the bottom of the board by digital multimeter, the resistance value measured is normal.

We didn't meet this problem before, what's the real problem? Because the boot current is larger than normal value, so we are going to measure the boot current after removing the U2 IC, but the problem still there. Measure the resistance value of the bottom pin of the iPhone U2 IC, we found the F4 pin PP3.0V is short circuit.

After check iPhone schematic diagram via WUXINJI Dongle, we know that this circuit has big power, fingerprint power supply and U5411_RF.

Supply power to the iPhone to boot it again, we found the U5411_RF is overheating, remove the 2 components that next to the U2, the iPhone is turned on, we confirmed that this iPhone problem is caused by damaged U5411.

The iPhone boot current jumps from 300mA, the iPhone displays white Apple and won't enter the iOS system. Installing the iPhone touch IC, the new faults comes out after testing, the iPhone has no service and no IMEI after booting.

For this drop-damaged UMT motherboard baseband failure, remove the iPhone baseband CPU, and use QUICK 861DW hot air rework station to solder the jumper wire to V1 and U1.

After soldering the jumper wire, solidified it by painting green UV oil, and then reballing the tin on the iPhone baseband CPU.

Now, install the iPhone, press the iPhone power button, after entering the IOS, touch the iPhone touch screen, now it reponses smoothly.