Normal Current While iPhone 6S No Display

Got this iPhone 6S which happens no display but normal current, we doubt the  iPhone PCB Board  may occurred something abnormal. We check it by   DC power supply, of courser, the current and voltage shows normal, but the screen still can't show normal. But during we check it, we found a faint light in the side and the pcb board is very dirty which has some solder flux, we doubt this isn't new phone. We decided to disassemble it.

Now we're going to use Fluke 15B+ Digital Multimeter to measure positive and negative 5.7V on the iPhone display touch power supply tube, the voltage measured is less than 2V. Next to measure the voltage of boost capacitor, the voltage only is less than 2V. Now we know the boost circuit is a problem.

Because the display touch power supply tube has been replaced on iPhone 6S, so we don't need to replace it now, the emphasis is on boosting inductance and capacitance. After measuring the inductance, we found that it was no problem. Then the problem is centered on the capacitor.

Open WUXINJI Dongle to check iPhone schematic diagram, we know this boost capacitance is C4002, we decided to replace the capacitor. With the help of QUICK 861DW, we replace it smoothly and quickly.

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Assemble the iPhone to test, the screen displays normally now. Continue to test other functions, all is fine, the fault has been solved. The fault is on this small capacitor.

Deal Way for iPhone 7P Large Current

Fault Description:

Large current occurred in the iPhone 7P motherboard 

First Step:

Test it with the DC power supply ,then we get a 3.8 V value. We doubt there has a short circuit.

Following the repair process.

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Pick up the fault and solve it, then clean it in the water inlet, gently fix the trouble and test the whole function after screen installation, now all other functions are normal, but there is no service on the iPhone 7 Plus.

Observe the radio frequency section under the Trinocular Stereo Microscope  , we find the reception of the front end is corroded.

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The fifth trace supply power for RF 1.8V, there is a serious corrosion and the layer is burned, scraping the bottom circuit to solder jumper wire.

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It should be noted that this line is the same as a three branch road. If we want to connect the two sides to the bottom and scrape the bottom, if we are not familiar with the circuit, we suggest to scrape up the circuit and check it, then scrape the trouble layer, it's better to carefully do the operation with specialized cell phone repair knife so as to avoid unnecessary troubles.

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After we finished the above step , we find a screen connected with this motherboard, we boot it and the screen shows normally, no unstable current produced.  The repair result is success.

Process to Repair iPhone 7P Won't Turn On

As of the water damaged, this iPhone 7P can't show normally which half bright and half dark.

The first step ready work is to check the voltage and current, then we will know which failure happened in this phone. 

Repair process

1 After we got the value ,we need to use JM-P01 Essential Toolkit to disassemble the iPhone, remove the iPhone motherboard and then put observe it under the VGA Camera 7-45X Trinocular Stereo Microscope, there has traces of water, and many small original components have been torn down.

 

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2 Connect iPhone motherboard to the computer with C48 MFI USB Cable, there is no response. With the help of YH898D hot air gun and tweezers, we remove the iPhone NAND Flash, and then connect it to computer again, still no response.

3 Use Fluke 15B+ Digital Multimeter to measure the booting power supply and I2C bus, the data is normal. Now we start checking the disconnected iPhone NAND flash that without connecting to the computer. Remove USB tube U4001, measure the resistance of the substrate, we found the E4#(PMU-AOP-TRISTAR-ACTIVE-READY) is short circuit.

4 Open the WUXINJI Dongle to check the iPhone schematic diagram; We can know that this point is connected to the CPU display IC U3703 C2#. So we remove the U3703, and then measure the C2# and U4001 E4# again, the short circuit fault has been resolved.

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The Last Three Steps:

1 Reinstall the  iPhone NAND flash and U4001

2 Replace a good U3703

3 Test the current and voltage 

After we get the normal value, we boot it again and wait for 10 minutes, everything is okay which means the fault was repaired.

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iPhone 6S Boot By itself

With  the intelligence phone development rapidly,  it seems the phone has its own brain. Recently we received an iPhone 6S which can boot by itself, its master said it has been repaired twice . We will be the third shop to repair it, maybe this time is the last time. Let us start the repair process....

After getting the phone, we carefully watched the mobile phone mainboard repair situation, and found that the barometer of the mobile phone was soldered with 4 or 5 jumper wires, but we have no idea what was the fault was fixed at that time.

Observe the iPhone 6s motherboard with a professional Trinocular Stereo Microscope, it is found that there is a small dot near the barometer disappeared. Checking the WUXINJI

 iPhone schematic diagram and bitmap, we get to know it is a zero ohm resistor. 

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After the short connection and installation, the iPhone 6s is tested OK. In order to ensure that the customer will not get any problems when he receives the handset, it will not be a problem if he wait for a night, until the second day morning, we found sometimes it still reboot repeatedly.

Is there a small hole in the barometer that causes a partial damage to the barometer? A barometer is directly found on the dismounted iPhone 6s motherboard, apply high temperature glue on the small hole and blown down the barometer with hot air gun. After the barometer replacement, the iPhone has no reboot failure after waiting for 2 days.

Then we back the iPhone to our customer,  he is so happy we fix it , we like to collect this smile .

But we have some tips sharing: Before you want to repair your iPhone ,please check the problem ,the ensure problem; then find a professional shop team. Or your phone will be hurt again and again and no good result finally.  Especially the part of phone CPU. 

Effective way to Handle iPhone 6S Fingerprint Failure

Fault Description:

The iPhone 6S can't recognize your fingerprint as of the water damaged.

According to the former experiences, we doubt the short circuit or the touch screen failure.

Following the solve way:

Disassemble the iPhone by JM-P01 Toolkit, carefully remove the iPhone motherboard. After checking, we found signs of corrosion in the fingerprint socket, and then detect MESA_TO_BOOST_EN_CONN.

Use Fluke 15B+ Digital Multimeter to measure the diode data of PP16V5_MESA_CONN fingerprint boost boot signal and 16.5V, the data is normal.

Observe the iPhone PCB board carefully under the VGA Camera 7-45X Trinocular Stereo Microscope, we found something else. The bottom pin was severely corroded after the corrosion was removed from the fingerprint boost U4040. A2 pin PP_VCC_MAIN is disconnected, and the A1 pin CND close to PP_VCC_MAIN is dropped by corrosion.

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Soldering the jump wire on A2 pin via Quick 861DW, but the fault still exists. Why is there such a problem? There are no problems anywhere else, L4040 boost inductance is normal after checking.

We have to rearrange the repair ideas, and then re-check it. Most of the time, we're only one step away from fixing the iPhone, it depends on the details. Open the WUXINJI Dongle to check the iPhone schematic diagram, we found this boost IC bottom pin only has two GND.

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Someone would say, the ground is interlinked, that's definitely not a problem. The iPhone motherboard GND must be connected. However, after measuring, the two ground of IC bottom pin is disconnected, which means these two are indispensable. If one is missing, it will cause U4040 not to work. After weld the jump wire, the problem of fingerprint that don't have 16.5V has been solved.

Install the iPhone and turn on it to test, the fingerprint entry is normal, now you can add fingerprint on your iPhone. Test the other functions, all is fine.

Fingerprint bottom pin GND cannot be ignored, because it can cause U4040 IC not working. During the repair process, you can ignore any place that might cause problems. Just be careful and patient.

Handle iPhone 6 No Wi-Fi Failure

The customers send an email to us about hers iPhone without Wi-Fi connect , it is the third time she sent to the repair shop . We disassemble it and found lots of solder flux covered on Wi-Fi and the nearby resistor was lost, the bottom of Wi-Fi was scrapped to copper wire. We doubt there exist others failure which caused the Wi-Fi Module problem. Let we start to the check.

First remove the Wi-Fi and boot device to measure the voltage of Wi-Fi  bottom board pin, we find that 14 pin has no signal voltage, it should be 1.8V. The problem comes from here. Using a digital multimeter to measure but no resistance, so we use WUXINJI bitmap to check and find it is directly through CPU, is it the bottom board wire disconnection?

It can be seen from the bitmap 10-25-1 that the iPhone 6 bottom board wire is really disconnected.

Now we have to see if there is another way, continue to look at the principle diagram Apple 6. As shown in picture 10-25-2 and 10-25-3.

This reset signal has a capacitor and a pull-up resistor. The capacitance is next to Wi-Fi . There is no resistance in the measurement. This is hopeless, then we look at the pull-up resistor again, find it is on the back of the iPhone 6 CPU from the bitmap, and it's very close. Measuring resistance is 446, then directly solder jumper wire, install Wi-Fi , but the icon is still gray. Then we think the Wi-Fi  may be broken. Immediately replace a new Wi-Fi  chip, Bluetooth is shown up, Wi-Fi  also appeared, the fault is fixed now!  As shown in Picture 10-25-4:

Effective Way to repair Weak iPhone 6P Wi-Fi Signal

No other damaged occurred in this iPhone 6P, the customer said the weak Wi-Fi  bothered him for a long time. So we got it and test it with the multimeter , no abnormal value about current and voltage ,the fault  shown in picture 10-4-1:

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Repair process:

Step 1. Install the iPhone 6P motherboard to test WiFi signal. Obviously, It's weaker than a normal mobile phone.

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Step 2. Remove the motherboard to check, the WiFi connector circuit is not damaged, in many cases, most of repairmen would directly replace the iPhone WiFi IC if WiFi itself gets damaged.

Step 3. Since we have advanced equipment with VGA 7-45X Trinocular Stereo Microscope to do careful observation, the motherboard is very beautiful, there is no water damage trace, the first consideration of fault is pressed parts.

Step 4. Indeed, we can see the IC be pressed under the microscope , of course, do not first think that WiFi itself under pressure, sometimes the next filter will also suffer pressure. The following picture 10-4-1 is pressed IC fl_cell_rf with false welding, also with minor cracks.

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Step 5. Take care to remove the IC and the small inductance. Losing inductance will also cause weak WiFi signal, of course, it is also possible to solder jumper wire to solve this kind of situation.

Step 6. Reinstalling IC fl_cell_rf to test WiFi signal, the problem is successfully solved now!