Professional Cell Phone Repair Guide

If there is only 2G signal on your cell phone and no 4G signal, this means that there are some problems in the 4G signal parts. This happens only after your mobile phone is water damaged, and the water intake is in the 4G signal channel. Open the iPhone 7 and remove the motherboard to observe under HDMI camera stereo microscope , but we can't observe any traces, so we are going to remove the 4G power amplifier chip. Remove the TDDPA_RF 4G power amplifier chip and measure the resistance value of the pad with Fluke digital multimeter. We found that the value of 11 pin MLB_PA_VBATT is infinitely large to the ground, it seems that the part is broken. As shown in picture 17-9-1. Connect  WUXINJI dongle  and check the circuit diagram on computer, we can see some voltage go to TDDPA_RF and MLBPA_RF2 chips, and the MLBPA_RF chip was not installed. The voltage is PP_PA_VBATT, which is renamed to MLB_PA_VBATT by R7113_RF resistor. The R7113_RF resistance has been corroded u...

We received a damaged iPhone 7 Plus, the malfunction is iPhone 7 Plus can't turn on. First, we need to connect it to the DC power supply to test the charging current of iPhone, the current will jump to about 200 Ma, which is unstable. The computer is unable to identify iPhone when connected, and it cannot be activated. Disassemble the iPhone to have a test, opening tools are essential to tear down the iPhone, then remove the iPhone motherboard. Measure the iPhone motherboard with Fluke 15B+ Digital Multimeter , there is no current, which means no leakage. Trigger it and it shows large current, the current up to 1.9A. Now, apply some rosin on iPhone logic board and use QUICK 861DW hot air rework station to heat, it's turning white. Does the iPhone main power break down? Let's check iPhone bitmap on the WUXINJI Dongle , we found the iPhone Nand flash power is  also   in the hot spot, first we need to measure the iPhone Nand flash to check if it is short c...

We are going to repair an iPhone 6s Plus device today, the main fault is that the phone shows no service after plugging in SIM card. Any parts get damaged? In this article, we'll show you how to diagnose and repair the problem! Depend on preliminary judgement, there are generally 2 parts get fault for no service phenomenon: signal channel part or REFF bus. You have to distinguish carefully when testing cell phone. After inserting SIM card, we can see the serial number when dial *#06# on dialing interface, as shown in 17-7-1, it seems that it is not the problem of the REFF bus, so we can exclude the fault caused by the bus (if the bus caused the fault, it will not enter the serial number after dialing the *#06#). The operation option on the interface as shown in picture 17-7-2, so it means there is no problem with the receiving section. Let's check the launch section. Take off the iPhone 6s Plus logic board and measure by Fluke digital multimeter , we found the r...

The iPhone 6S fell into the water before, then it was stuck on the white apple logo after rebooting. It has been repaired once, when we receive it, iPhone 6S reboot occasionally in white apple state. After removing the logic board, we found that the iPhone U2 IC and tube have been replaced. First of all, we decide to use 3.5X-90X Stereo Zoom Microscope  14MP HDMI Camera to check motherboard, there are small beads around the chip, which is a serious mistake. Clean up the iPhone logic board and then replace the new U2 IC and charge tube, but the problem still the same, iPhone stuck on white Apple logo and restart occasionally. Measure the diode data for iPhone battery detective pin  with Fluke 15B+  Digital Multimeter , the data is normal, the resistance of iPhone booting condition is normal, and the voltage also is normal. For water damaged iPhone,iPhone system is less damaged. After confirming to customer, we start to flash iPhone. Connect iPhone to comput...

As we know, iPhone X is the latest iPhone models designed with many new features, obviously it's one of your best choice when choosing cell phones, but there are some faults you can't avoid whatever cell phone you use. In this article, we are going to repair an iPhone X charging fault. First of all, be clear about the iPhone X charging principle, we can check on WUXINJI Dongle . Plug iPhone data cable, the iPhone tail plug connector J6400 47/48 pin gets 5V input voltage PP_VBUS1_E75, at the same time, the 20 pin HYDRA_CON_DETECT_CONN_L will be pull down. 5V of PP_VBUS1_E75 send to U3300, after R3360 output PP_VBUS1_E75_RVP, finally sent to U6300. HYDRA_CON_DETECT_CONN_L is renamed HYDRA_CON_DETECT_L by R6410. HYDRA_CON_DETECT_L send to the multifunctional electronic switch tube U6300 G3 pin, when the U6300 received a low power lever signal, then access identification iPhone lightning cable . If U6300 received the 5V power supply, and detected after th...

We received an iPhone 7 device from customer, it is not turning on. This is a common failure for iPhone repair technician. How to test and repair the failure step by step? Let's check in the article! Tear down the iPhone 7 and connect DC power supply  to test, the reboot current stuck at 50mA, and the device can not be online. We also met the same situation on iPhone 6 devices, so we know the 50mA reboot current is often related with CPU, U2 and display power problems. Considering the online failure, we replace U2 chip first, the result is the same. Disassemble the CPU shied cover and observe the iPhone 7 CPU chip under Stereo Microscope , we found the CPU attached well without any track of cracks. 50mA is unable to measure the voltage, so we have to first measure the resistance on the circuit of restart conditions. After the iPhone CPU  and NAND are measured, continue to measure clock, reset and bus. We found the fault is from the clock. The output resistance of the...

IPhone 6 has a white apple logo on the screen when turning it on. This screen has been replaced after falling. How should we repair the problem? Let's check the expert repair process in this article, hope it will help! According to our past repair experience, we know that the dropped device should be directly checked on its CPU parts. First of all, check the bus and reset, both of them are normal. Cut the shiled cover above the fingerprint, use Fluke 15B+ digital multimeter   to measure the resistance of CPU to the clock and data. The normal values of R0317 and R0316 are more than 400, the measurement of R0317 resistance is 745, and the R0316 is 479. This case is mostly the two pin of AP31 and AR31 in the right lower right corner of CPU has pseudo soldering. First press the iPhone 6 CPU  to test whether the device can turn on or not, do not try to reflash the phone first, it will report error 9. Of course, the best method for CPU pseudo soldering is redo the parts...

What are the characteristics of iPhone 7 backlight failure? According to our maintenance experience, we will encounter some common situations, such as iPhone touch screen does not show, the screen light is dim or can not adjust brightness. In this article, we will introduce how to repair iPhone 7 backlight failure step by step. At first, we connect WUXINJI Dongle  to check iPhone 7 backlight power supply schematic diagram.  By reading the iPhone schematic diagram, we know that the iPhone backlight boost IC  output three sets of backlight power supply signals, they were PP_LCM_BLANODE (16.5V Cathode Voltage), PP_LCM_BL_CAT1 and PP_LCM_BL_CAT2, these three circuit signals are sent to the display interface via three inductors respectively, the pictures as follows.     The three inductors are easy to damage, and then cause iPhone to have no backlight or light instability, sometimes bright, but sometimes not bright. In this case, we can repair i...

We are going to repair a iPhone 7 with charging failure, first of all, we need to know the working principle of charging part. The 5V charging voltage PP5V0_USB sent by the charging interface is sent to the charging IC, then it is sent to the charging protection tube and sent to USB control IC. The charging protection tube is easy to damage, resulting in only available for charging while turning off the iPhone 7. It won't charge after turning on, prompting "do not support this accessory". The iPhone 7 USB control IC damage will cause charging and online failure, prompting unrecognized USB and no support for this accessory, it may also cause a failure to stuck on white Apple logo while turning on the iPhone. How do we repair the charging fault? it can be solved by the short connection, we can check the iPhone 7 charging part schematic diagram by WUXINJI dongle as shown in picture 1-1, the detailed repair steps are as following: 1.Plug in data cable and use F...

If the touch function fails to work, you'll be unable to control your cell phone very well, which part may get damaged? How to repair this problem? Let's have a look in this article! First of all, connect  WUXINJI Dongle  to check the iPhone 6 touch part power supply circuit.  We can see from the schematic diagram of  iPhone touch IC  -- U2401 has two sets of power supply circuits, one is 1.8V power supply PP1V8_GRAPE that comes from iPhone power IC U1202, it can be measured in capacitor C2403, the other one is 5.1V power supply PP5V1_GRAPE_VDDH that comes from U1501. And the iPhone touch IC-- U2402 has three sets of power supply circuits, PP1V8 comes from iPhone power IC  U1202, PN5V7_SAGE_AVDDN is -5.7V that comes from U1501, PP5V7_SAGE_AVDDH is +5.7V that comes from U1501. The voltage for PN5V7_SAGE_AVDDN and PP5V1_GRAPE_VDDH can be measured when the iPhone display screen  is lit ， the data is +5.7V and -5.7V. The voltage for PP1...

We are going to learn how to fix iPhone 6S Plus with different types of fingerprint function failure today, how should we fast find out the damaged part and repair? Let's follow the article step by step!   Connect the WUXINJI dongle  to the computer to check schematic diagram of the fingerprint flex cable interface. As shown in picture 1-1.   By reading iPhone 6S plus fingerprint flex cable interface diagram, we can find that it is a little different from the iPhone6 plus circuit. The left side is the control signal of the fingerprint section. The right side with MAMBA is the newly added functional Force Touch, which is called the piezo touch, for example, the reactions are different between gently point the desktop clock icon and pressing the icon by force, as shown in picture 1-2. We conclude three situations for iPhone 6s plus fingerprint failures: 1. if the power supply is normal, the resistance of each pin is required to measure in turn. If there is an d...

Have you ever met the situation on your iPhone 7 Plus? If it has a charging problem, such as iPhone 7P will not charge, can not connect to PC, iPhone charging icon percentage decrease, stuck on white apple, etc. all these charging problems, you need to check iPhone 7 plus charging part. Check iPhone schematic diagram on WUXINJI Dongle , 5V charge voltage PP5V0_USB   sent by the tail-plug interface ， one circuit is sent to iPhone charge IC, one circuit is sent to iPhone USB control IC. The repair method is as follows. Disassemble the iPhone 7 Plus with phone disassemble kits ,  remove the iPhone motherboard. Measure the 5.0V voltage (PP5V0_USB) next to the iPhone charging IC  with Fluke 15B+ Digital Multimeter  to check whether it exists. If not, then you need to replace the new iPhone tail plug flex cable. If yes, continue to check. Measure the 5.0V voltage (PP5V0_USB) next to the iPhone USB control IC  with multimeter to check whether ...

We are going to fix an iPhone SE device today, according to the owner's description, the main problem is that it fails to turn on, also , there is power leakage phenomenon. How should we solve this problem, let's check in the article! First of all, open the iPhone SE and remove motherboard to test, the battery interface is the same as iPhone 6P, if there is no professional 6P  DC power supply  interface, you can also replace by ordinary alligator clip, as shown in picture 1-1. The battery positive voltage VBATT is first sent to the charging IC-U2300, and the charging IC-U2300 outputs the main power supply VCC_MAIN (same as the battery positive voltage value) to the main power supply U2000 and other related circuits. There are 3 situation you may encounter: 1. If iPhone SE is unresponsive after turning on, first measure whether there is the main power supply supplied by U2300, if not, you need to replace U2300, if the main power supply is normal, the problem is fro...

We are going to fix the backlight problem on iPhone 7 Plus, before repairing, we need to check the schematic diagram on WUXINJI Dongle , there are two sets of backlights, one is on the left of the iPhone display screen, and the other is on 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 damag...

We are going to fix a iPad Air2 today, the main problem is that the screen is blurred, it reboot again and fails to enter into the system. It's a common problem on iPad devices. It's not a big problem if you have enough repair experience. How shall we repair it? Let's follow the article step by step!                                     First of all, we connect the iPad 2 on computer and reflash it by iTunes, error 4013 is reported, so we judge the problem comes from flash memory. Dissaemble the iPad Air2 by  iPad opening toolkit , and take off the iPad motherboard, we found the iPad NAND chip was repaired before, so we remove the Nand chip and reflash again, the error code is reported again. So we are going to directly repair flash memory. After the flash memory is installed, it's normal when reflashing again, the invalid SN is reported. If the invalid SN is reported, it basicall...

This iPhone 6 device has been repaired before, the main fault is the charging problem, although the screen shows a charge icon, but the power does not really enter the mobile phone, and the phone reboots sometimes. After receiving this fault cell phone, we found that the main board charging chip, battery and accessories were replaced before. 1. M easure the voltage of (C1408, C1700) USB were given to U1401 charge tube and U1700 (U2), the both 5V value are normal. 2. Remove the U2 and charge tube respectively, measure the bottom voltage to see whether the iPhone 6 motherboard   has broken cables, the result shows that the two chips are all normal. 3. Replace the two new chips and charge to have a test, the fault is same as before. 4. Connect the iPhone 6 with computer, It displays no data  for the battery life  on Ace assistant, this often happens on iPhone 6 and iPhone 6P, basically it's caused by the problem of CPU to the charge tube battery detec...

We are going to fix the iPhone 7 device today, according to the owner's description, the main fault of this cell phone is the weak WiFi signal, the problem was repaired by a repairman before, but the same problem happens again, why? Let's find out the solutions from the article!   1. Opening the iPhone 7 device with specific iPhone repair opening toolkit . 2. The iPhone 7 WiFi parts was replaced before, but we still doubt it's a problem. 3. So we take  QUICK 861DW hot air station  to heat the WiFi with suitable temperature, then use tweezers to remove the WiFi chip. 4. Solder a new WiFi chip on the iPhone 7 solder plate, turn on and test the WiFi signal again, the fault is still existing. 5. Then we estimate the problem is from the iPhone signal receiving part 6. Connect jumper wire on iPhone 7 logic board. When solder jumper wire between the tiny components on logic board, you need a Trinocular Stereo Microscope  for more clear observa...