The next repaired iPhone occurred the weak signal problem, according to our experiences, we doubt there exist some IC damage in motherboard, let us start our fix process.
Following the repair process:
1. iPhone 7/7P has no signal at all, infinite search.
Get into IOS, go to Settings>- General>- About to check whether there is the IMEI.
If the IMEI is not displayed on this iPhone, then you need connect iPhone to DC power supply to check iPhone boot current, and then determine if it has a large current issue. If there is a phenomenon of leakage, then you can fix it with leakage methods; if the current is normal, then you can directly replace the baseband power without test, and then re-install the iPhone baseband CPU.
If IMEI is displayed on the iPhone normally, then set up the time （WiFi Automatic settings available）， enter the Dial-up interface, press *#06# to see if the IMEI can be displayed. If IMEI can't be displayed, then you need to use hot air gun and tweezers to replace Power Amplifier IC-QPOET_RF, and replace baseband power BBPMU_RF, re-install the baseband CPU--BB_FR, replace LBPA_RF, replace MHBDSM_RF.
2. iPhone 7/7P has no signal at all, try different SIM card
Press *#06# and the IMEI can be displayed normally, and then you can try insert different SIM card to check. If you insert any SIM card, it still shows no signal, and then you can check the antenna under the Trinocular Stereo Microscope, and then replace it, replace MF IC and Power Amplifier IC-QPOET_RF.
3. Some damaged IC will cause different SIM card has no signal
It is noteworthy that if system under the hardware abnormal case, then the 4G function will be auto close. If there is no 4G or even you fixed the hardware, but still no 4G, you can erase all the data and then restore settings.
After we analysis the phone detail , we can know the sources fault, but if we need to fix it, we still need to disassemble it and check which IC cause this fault.
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