跳至主要内容

Solution: iPhone 7 Won't Turn On Failure

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 first pin of 24M main clock is only more than 200, the normal value of the first and third pin should be more than 800. As shown in 17-3-1.
 

First remove the associated capacitance C0702, the result is same, so the surrounding small resistance is necessary to be replaced, directly take the main clock to measure the bottom pin (quickly taken down at high temperature , we use QUICK 861DW Hot Air Gun with straight nozzle at 420 degrees.)

The resistance of bottom is all normal. Replace a 24M main clock (common used on 6S). After replacement, it can connect online, and also ok for flashing.

More iPhone repair tutorials, please feel free to contact on www.vipfixphone.com

评论

发表评论

此博客中的热门博文

Solution: iPhone X Won't Turn On

According to the customer's description, the iPhone X would not turn on after it drop accidentally. Then the cell phone reports error 56 when restore it. How did this happen? Let's test and repair step by step. Since iPhone X motherboard 2 layers are connected through the middle column, the solder points are very easy to get dropped. so we guess that the solder points from NFC chip to the CPU part have fell off. Disassemble the iPhone X by iPhone opening tools , remove the upper board off the main board, when separate the main board we see there is a row of points have fell off. Check the location map on WUXINJI dongle , it is surrounded by a ground wire, in fact, there are 6 useful points dropped. The ground wire does not need to be filled, the 6 useful points are added by professional phone welding tools. These are the signal wires of the NFC chip, so the iPhone X would report error 56. Then the tin of the middle column is repaired by iPhone X BGA reballing ste...
发表评论
阅读全文

iPhone 6 Display Failure after Replacing LCD

The iPhone 6 display is black after replacing LCD. After checking, the diode data of display socket is normal and all power supply for iPhone display IC  output is normal. Testing by  DC power supply , we find the iPhone current is abnormal. When press the iPhone power button, the boot current is obviously large. The current reached 100mA when press the power button. After remove the display tube, the current still the same, which means there is a short circuit. Measure the voltage output of each circuit of power supply with Fluke 15B+ Digital Multimeter , then surprised to find that there are really short circuit places. LD010 is short circuit; we suspect that the filter capacitance on the circuit has been penetrated. After remove the iPhone power control IC , we found it is ground short circuit. Open the WUXINJI Dongle  to check the iPhone schematic circuit, we found that this circuit is the display card image transmission MIPI data bus power supply. CPU brea...
发表评论
阅读全文

Solution: Why iPhone X Voltage Keeps Jumping

After getting the iPhone X motherboard to test, we observe the current value repeatedly jumps between 0mA and 50mA on DC power supply , and it is different from the normal booting current. Next, test whether the power supply of every circuit is normal. PP_VDD_MAIN is measured 4.2V; PP_VDD_BOOST measured is 4.2V. PP1V8-ALWAYS is 1.8V, all the values are normal. But when testing PP1V1_S2, PP0V8_SOC_FIXED_S1, PP1V8_S2 and other circuit voltage that output by power chip U2700 voltage are jumping constantly. According to previous experience, voltage jump is usually caused by a power supply circuit of U2700 output. Measured with digital multimeter , there is no short circuit was found for the dipole value of all power supply to ground. We repaired iPhone 7P before and know that if crystal oscillator is false welding can also cause voltage jumping, And if iPhone CPU  power supply is abnormal also can cause voltage jumping. Check the crystal oscillator we find no problem, then check th...
发表评论
阅读全文