An iPhone 7 runs slowly, so the users try to speed it by updating IOS, after finish the IOS update VIA iTunes, the iPhone cannot be turn on, it’s stuck on the Apple logo, and sometimes auto restart. Connect it to the computer and flash it to latest IOS, the computer prompts the flash is finished, but the iPhone still can’t enter the activation interface, and always shows white Apple.
Test iPhone by DC power supply, the power current is stuck at around 150mA. Touch the iPhone home button, it have response, the flash can be completed normally, which means that the iPhone booting condition is normal. Remove all iPhone external accessories, and then test it again, the result is the same.
Press the iPhone power button, after a while, it gets into interface, but the iPhone still runs slowly, and we found that if we clicking on the file or interface related to the sound, the iPhone will get stuck and stop running. As we know, the iPhone 7 audio IC is easy to damage, so we decided to take out the U1301 big audio to check.
Before we take out the iPhone audio IC by using QUICK 861DW hot air rework station, we need to protect the other ICs next to it ( below it is iPhone Nand flash, above is a iPhone large power IC, on the back is the iPhone baseband CPU)
After remove the iPhone big audio IC, we found the problem on the solder pad. The solder joints of the two pins of the chip C12 and J12 have been lost. Observe it under the 7-45X Trinocular Stereo Microscope, finding that the jump wire between C12 and J12 is easy to disconnect. Check iPhone schematic diagram on WUXINJI Dongle, there are 2 capacitors next to this audio, there are two resistors next to the audio lead to these two points respectively.
Welding jump wire to these two points respectively, the probability of C12 disconnection is relatively large. it is a signal that the CPU gives to audio. The iPhone big audio IC doesn’t need to replace the new one, just re-weld tin to old one, and then install it.
After installation, press the iPhone power button, after for 20 seconds, the iPhone get into IOS interface. Test all functions on iPhone, everything goes well.