Professional Cell Phone Repair Guide

Received an iPhone 6, the fault was that the iPhone sometimes display normally, but sometimes not. Open iPhone 6 to test, iPhone LCD display does not show anything. Removing the iPhone motherboard and looking under a stereo zoom microscope, it was found that there was a lot of solder paste in the socket of the iPhone monitor and the socket of the iPhone touch. Is that the socket not clean? First we use BGA clean water to clean the iPhone motherboard, after cleaning, we can use digital multimeter  to measure the grounding resistance value for the J2019 display socket 1 pin PP_LCM_BL_CAT2_CONN and 4 pin PP_LCM_BL_CAT1_CONN, these two pins will cause iPhone screen half bright and half black problem. We found the resistance value of 4 pin is 2111, which is abnormal, the normal resistance value is about 570. After short connection of the FL2025 fuse inductor, the resistance tested is normal. Assemble the iPhone display screen and test it, the Apple logo can be disp...

The client delivered iPhone SE to us. The fault described is short circuited by mobile phone and cannot be restarted. For the similar failure, how do you often solve it? Let's check in the article! First, remove the motherboard and feel the location of the heat with your hands. However, the location of the heating unit is not obvious. Apply some rosin on the motherboard and connect DC power supply again, we still can't find the fault part. The circuit is converted from battery to main power supply through the conversion tube Q2300. Remove the Q2300 and measure the grounding resistance with the Fluke multimeter to see if there is a short circuit in the battery or the main supply. It is found that there is a short circuit in the main power supply connecting component by value evaluation. Rosin some rosin on the main power supply connecting component again. The C2331 melts instantly when the single circuit is energized. It seems that the fault point is here,...

A client sent us a iPhone 6S, according to his description, the phone did not fall, no water damage, but it suddenly had no response to the charger. Why did this happen, let's diagnose and test step by step. First of all, open the iPhone to test it. It leaks 100mA, turn on the phone, it can enter iOS normally. The replacement of external configuration and charging is still unresponsive. The test voltage of iPhone battery socket is only 0.6V. According to our repair experience, it was caused by U2. Remove iPhone U2 IC, but iPhone still leaks 100mA, and the resistance of the bottom pin is normal.  Replace the new iPhone U2 IC, assemble iPhone and test it. It charges reasonably. After a period of time, even if we do not use iPhone, the battery is still burning fast. We need to find out where the loopholes are. Remove the iPhone motherboard again and connect it to DC power supply  to test, after heating a while, we can feel the iPhone WIFI IC is overheat. 6S and late...

The iPhone 7P displays the iTunes icon, and when it connects to the computer for recovery, it reports error 56. When it reaches 80%, the error code is the same as the previous model, usually caused by camera power and NFC. The resistance of each circuit power source of the camera is not abnormal. Checking the NFC section has a common fault in iPhone 7P. The NFC power supply can connect the short circuit at the upper left corner of the CPU. Short A1 and A2 pins in the NFC power supply tube, then restore to short after the test connection. This iPhone 7P is still unable to pass, so we can only take NFC to test. It is no problem to test the resistance of the socket by Fluke digital multimeter , reball the NFC module with iPhone BGA reballing stencil , install the NFC module and restore the phone after installation, but the mobile phone does not carry out the second self-examination and jump to iTunes, computer display recovery mode. There was no such situation before, so the...

We are going to fix iPhone X today, the fault was that the charging icon was displayed properly, but the iPhone X was not charged after charging. How to repair step by step?    After testing, the charging icon on the iPhone X is displayed properly, but the percentage of power on the iPhone is getting smaller and smaller when charged, which is actually a non-charging fault. According to our maintenance experience, the L3340 and L3341 inductors of the iPhone's rechargeable integrated circuit are prone to empty soldering and pin loss for a fallen damaged iPhone. Connect iPhone charging cable to the iPhone X tail plug flex cable, and then test the cathode of iPhone battery by UNI-T UT658 USB Tester , no voltage was found, so we judge the fault is in the charging part. If you want to delve into it, we have to measure it hierarchically, the AP part as shown in picture. The external conditions measured are normal, according to our experience, we suspect that t...

We're fixing the iPhone 6 today, the customer described the failure as WiFi can't be turned on. After removing WiFi, the activation interface appears. Connecting to the test, we found that the iPhone 6 WiFi chip was not installed, the data cable was not installed in boot-up activation mode, and when we connected to the AISI assistant, we found a serial number with no baseband. After a period of use, it enters the activation mode again, usually based on our usual maintenance experience of baseband power output short circuit. Considering WiFi removal, the GPS power amplifier associated with the WiFi edge has a voltage output baseband power. Measure with a FLUKE digital multimeter , it's PP_LDO13 as shown in picture. After eliminating the short circuit, the result is that the C5129 is broken, the resistance is back to normal, connecting Aisi assistant we find the baseband out. Using Ace assistant to skip WIFI, activate the backward menu again and use it properly. ...

We received the iPhone 6 plus, the customer described the failure as the iPhone 6P the ground, and the iPhone 6P did not respond to the touch. As you all know, M1 pin easy to disconnect is a common fault for the iPhone 6P, whether the iPhone is down or used for a long time, this should be a design flaw in the motherboard. The M1 pin is a synchronous signal from the iPhone screen to touch communication. The trouble is that sometimes the touch doesn't work at all and white lines appear above the screen.   Reboot to measure. After turning on iPhone, and touch and display function tested are normal. In this case, there is a way that touches this position of the front socket by your fingers (because the back is the iPhone black touch IC ), if there are some problem on M1 pin, then the failure will be shown clearly.  After testing, we start to repair. Disassemble the iPhone, the iPhone motherboard is good, the iPhone battery has been replaced.  R...

We're going to fix an iPhone 6P with WiFi failure. First, we need to check the phone to make sure that the WiFi doesn't work and that the other features are working. According to customer's description, the iPhone 6P device has been repaired before, but it has not been repaired very well. Disassemble the iPhone and detect the iPhone 6P motherboard  carefully, it is found that the WiFi module was not installed, also there are a lot of solder points fallen off. As shown in picture 1. Check the WUXINJI bitmap  and find out the 32K clock signal pin of WiFi is lost. Bluetooth synchronization control, clock and so on, Bluetooth foot position directly through the iPhone CPU . Then dig the pin to fly jumper wire and apply some green oil. Welding the original WIFI and turn on the iPhone to test, it's gray WIFI too, and the device also stuck. After we replace a new one, the fault is still same. Didn't the WIFI install well, we heat it directly and put the twe...

We received a iPhone 6 today. The main problem is that the signal of the iPhone 6 is so weak that the user can't use his iPhone properly. We'll give the best solution for this kind of fault, let's check it in the article! After receiving iPhone 6, observe the appearance of iPhone without obvious physical damage. Disassemble the iPhone 6 and connect iPhone logic board to the DPS DCpower supply  to measure its current, the current is normal. Press the iPhone power button to turn on the iPhone and enter the iOS to check the iPhone signal. After measurement, the signal is abnormal, very weak. Based on previous maintenance experience, there is an inductor L4608 powered by B + to the iPhone antenna switch, and we can open the Five Star Set package to look at the iPhone sketch to find it. After find out the problem, we need to short connect L4608. Put iPhone logic board under the StereoZoom Microscope , use QUICK 861DW  hot air rework station to solder ...

We're going to fix an iPhone 6 with a compass fault. First, observe the motherboard and find that there's no water, no pressure, and the current goes through a normal DC test. The gyroscope and gravity are normal, but the compass doesn't rotate. Then we directly removed the compass u1901ic and measured the pin resistance value, the digital multimeter shows that A4 pin has no resistance. Compass A4 pin is through u2201 coprocessor B6 pin, so we remove the u2201 and test with the multi-meter, it is found that the two pins are not connected, indicating there is a broken wire. After careful observation under Trinocular Stereo Microscope , it is found that there are tiny cracks in the screw holes under the GPS. In case of uncertainty, we find another motherboard and dig it out. Also use the multimeter to check the compass A4 pin and find the wire passes through here. Then dig it up and the cracks will not be removed. Use the jumper to connect. Using the multime...

A customer sent us a iPhone 6 to fix it. The fault described is that iPhone 6 will not turn on. But after testing, the real problem with this iPhone 6 is not shown after startup. How to fix it? First of all, use  phone opening tools  to disassemble it and remove the iPhone 6 logic board. The iPhone logic board looks good, no trace of water-damaged or traces of external pressure are found. Connect iPhone logic board to DPS DC power supply  to test it, the boot current tested is normal, but the iPhone LCD screen still no display, always keep black. Measure the resistance value of the J2019 by digital multimeter , the resistance value is normal. Now, measure the voltage, there are no positive and negative 5.7V, and we suspect that the U1501 is damaged. Remove the U1501 by Titanium Alloy Tweezers , and then install the new one to the iPhone logic board. After replacement, measure it again, but the 5.7V still can't be measured, we think the boost has so...

Customers delivered a iPhone 6 with recording sound fault, we'll test and repair it step by step. Hope the article will help you! First of all, replace the U0900 audio frequency chip, we need to make sure whether U0900 is damaged, after replacing it and reinstalling the iPhone 6, the recording function fault is still not solved yet. For a motherboard like this, it didn't get water in before, so we can only consider that the bottom of the board is broken, take off U0900 to measure the resistance value of the bottom pin by Fluke digital multimeter , it is found that the big audio A9 pin has no resistance value. This pin is a clock synchronization signal given to u0900 by the iPhone 6 CPU through the R0301 resistance, and if the circuit is broken, the cell phone will record without voice.  This kind of fault must be processed by fly jumper wire and directly from this resistor to the big audio A9 pin. You need to pay attention that the big audio requires very thin...

We want to fix the iPhone 6S, the main failure is that it can't recognize SIM card. The first step after receiving the call is to remove and check carefully. Before the iPhone is repaired, the repaired area is the baseband power, and there's a lot of solder paste in it. Use digital multimeter   to measure the voltage of each pin of the socket at the moment of power-on, all the SIM-RST SIM-CLK SIM-DATA have instantaneous voltage, only SIM-VCC does not. According to past repair experience, there are 2 problems in the power supply of SIM card: 1. baseband power supply; 2. capacitance resistance. The baseband power supply has been repaired, without considering power supply. It should be a small capacitor or a small resistor problem. By checking the WUXINJI circuit diagram, it is found that the small capacitance and the resistance are under the shield cover, carefully cut off a part of the shield, and observe the small capacitance under the Trinocular Stere...

Customers sent iPhone 6 with WiFi signal and SIM card service failure. After disassembling and checking the phone's appearance, the motherboard is found to have electronic shock before, and WIFI antenna terminals and GPS were scorched. The above situation resulted in no signal WiFi part was burned and the circuit was broken, connect the jumper wire and use green oil to solid in the corresponding part is ok. Now the WiFi part repair is completed. Next, we are going to repair the communication part. Remove the shield on the baseband part, measure whether there are the baseband bypass capacitance is short-circuited by electric shock, judge whether the iPhone baseband CPU is damaged, check the electronic components are relatively intact, the baseband is not pressurized, observe under the microscope , we find that the antenna switch has been burned. Direct replace the iPhone antenna switch, install the iPhone 6 to test again, the WiFi signal and no service problems a...

The iPhone 6S reports error 4013, after checking it, we found there are watermarks on the board and it is corroded near the base band. How shall we repair the problem? Test the iPhone motherboard with  DPS DC power supply , the current stuck on about 80mA, judged as a data-cable mode. Install the iPhone 6S and use iTunes to flash it, the failure still there, the iTunes still reports error 4013. At this time , we need to check the iPhone carefully to find out the fault part. First we check iPhone baseband circuit, if the iPhone baseband power is short circuit, if the resistance is normal and whether the 19.2 clock is normal. Replace the better iPhone baseband CPU , if the iTunes process bar can be moved, then iPhone baseband CPU may be damaged. After disassemble it, we found the corrosion phenomenon around the iPhone baseband power is very serious, first suspected baseband power supply. Use QUICK 861DW  hot air rework station to remove the iPhone baseband po...

Have you ever encountered charging failure on your cell phone before? We received a iPhone 6 with the same failure. Before repairing, we need to diagnose the reason. In this article, you'll get the best solution. The iPhone 6 was no response when charging, and there is no charge symbol displayed. Observe the iPhone 6 motherboard under microscope, it is a perfect board, the iPhone charging flex cable is good, and the resistance value measured by Fluke 15B+ Digital Multimeter   also is no problem. Since we didn't find the problem after measuring, we judge the iPhone U2 IC  might be damaged. Use QUICK 861DW  hot air rework station to remove the iPhone U2 IC, and then replace it with the new one. Measure the resistance value again  after replacing the U2 IC, the data is normal. So we test the iPhone charge function, the fault still there. Now remove the iPhone charge tube, and then measure the resistance value, we found the G3 pin is no resis...