Repair guide: iPhone 6S Plus no service after WIFI failure fixed

The iPhone 6S Plus has WIFI failure, after we fix it by ourself, the iPhone has no service, why it that? how to repair this problem? Here is an repair guide.

Firstly, we need to test the iPhone 6S Plus. Turn on iPhone 6S Plus, insert the SIM card, the iPhone shows "no service". Check iPhone carrier signal, it can be manually searched, but unstable.

Continue testing, the signal is normal when you turn on 4G in Cellular Data, it can connect to the 4G network. It's normal to make phone calls and browse the Web，but the signal is bad. Turn off 4G, and then choose 3G and 2G, both of them are showed no service.

The 4G signal can be searched normally, but 2G and 3G are no service, we suspected that the fault should be an iPhone antenna switch or a 2G amplifier.

Is it an error in the antenna switch frequency selection? We decided to replace the antenna switch and test it. After remove the antenna switch, use digital multimeter to measure the diode data, we found the 21th PP_2V8_LD014 power supply of the ULASM_FR antenna switch is grounding short-circuited.

Open the WUXINJI Dongle to check the iPhone schematic diagram, we found the PP_2V8_LDO14 is connected to many places, one of them was sent to the filter U_VOX_RF next to the iPhone WIFI IC.

Measuring the diode data for all the power supply of filter, we found there are several power supply circuit are short-circuited.

According to the description of the customer, we judged that the fault is that the tin ball of the filter next to the iPhone WIFI IC was burned when he repairing the iPhone WIFI IC.

Use QUICK 861DW hot air rework station and Titanium Alloy Tweezers to remove the U_VOX_RF directly，and then turn on iPhone to test, now the 2G, 3G and 4G signal can be searched normally, and the signal tested is normal.

After re-installing the U_VIX_RF, assemble the iPhone, turn on iPhone 6S Plus, now the iPhone signal is normal , it has service. Test the functions on iPhone, all functions tested are normal.

DIY FIX: Backlight damage causes iPhone 6 won't boot

 Today, we will share a iPhone repair guide that how to DIY fix backlight damage causes iPhone 6 won't boot. When we supply power to iPhone 6 with C48 MFI USB Cable, the iPhone always shows black screen. Let's learn to diy fix it!

Connect iPhone to DC power supply, we find current 80mA circularly run while connecting and triggering, so maybe it's USB damgage cause I2C short circuit during charging process, first remove the iPhone 6 motherboard and take the USB off, but it's still the same as before, then we measure the I2C resistance and power supply! It is found that the I2C 0SCL is in a short circuit state. As shown in picture 11-10-1.

Since it's short circuit, it means the connected chip is damaged, the connected chips have display, backlight, main power supply USB and the iPhone 6 CPU.

First observe with VGA Camera 7-45X Trinocular Stereo Microscope, it is found that all the backlight diodes are burning and discoloring.

Then remove the backlight first, it does not short-circuit. The trigger current is normal, so continue to replace the 3 piece of iPhone backlight chips.

According to our past experience, if the large inductors gets discoloring, the large inductors with connected iPhone backlight IC would also have problems, so we replace them together. As shown in picture 11-10-2.

Measure it again with DC power supply, now the current is back to normal.  At last, instal the USB, and turn on iPhone, it runs smoothly and successfully. Keep going to check other functions, all is fine. The repairs end!

Repair iPhone 7 Plus issues: no service, black screen, unknown error 56

Today, we will share a repair guide for iPhone 7 Plus issues, this iPhone is severely corroded by water, it cause many problems, such as black screen, no service, unknown error 56 and so on. We need to fix it step by step, please be more patient on it!

Rip off the motherboard sticker that can be ripped, and remove the iPhone PCB shield cover that can be removed. According observe, we find the most serious is the display backlight part. Now we can clean the iPhone motherboard first, and then measuring power supply C3405 with multimeter, it directly to the ground, careful observation under the microscope found that C3722 was severely corroded. After removal, the diode data of the main power supply becomes 298. At this time, connect it to power and phone standby leakage 30mA, press the iPhone power button, the iPhone screen is lit, but the left screen is dark. Leave it alone, enter the IOS, and insert the SIM card to test, we find there is no 3G、4G， the fingerprint is normal. It not only stuck on fingerprint setting, but also the restore network, restore all settings. Observing it under the microscope, we found that FL3901 corrosion seriously caused the left iPhone backlight IC cannot supply power. After soldering jump wire, it's back to normal.

Then found R7109 corrosion damage caused the power supply to high-frequency power amplifier circuit impassability, resulting in no 3G and 4G.  After soldering jump wire with rework station, it's back to normal.

Now we're going to solve the problem that stuck on iPhone. We want to backup first and then brush iPhone, then we found it can connect to PC, but when you connect to iTunes, it times out, dis U2 cause it? So we replace it with iPhone 6S U2 IC, but the problem still exists. So now we directly use DFU mode to forced brush iPhone.

However, when the progress bar shows 60%, it reports unknown error 56, re-flash several times, it still the same, the unknown error 56 most caused by NFC. iPhone Baseband CPU、camera power supply could also cause the problem, but these function all is normal, so we judged NFC. Observing NFC under the microscope, we found that it had a little corrosion.

Remove the NFC, and measure the diode data of NFC, we found the G2, D5 and C7 all is connect to ground. From the phone circuit diagram, these three points are connected to the NFBST_RF, as shown in picture 10-2-2, we directly remove it, G2 still short circuit. After remove the C7517, the resistance is normal; D5 and C7 also back to normal. Replace the chips on motherboard, and weld well, flash it again, it still reports unknown error 56. Water-damaged motherboard power supply is the easiest to burn, so we remove shield cover of iPhone CPU.

It can be seen from the phone schematic diagram, there is a group of power supply PP_VDD_MAIN_NFC converted by NFCSW_RF which from main power supply, so we can weld the jump wire from the A1 pin to the A2 pin.

Finally, once again brush iPhone, you can enter the IOS system now! Test the functions, all is fine, the repairs end!