Tutorial: Tell You How to Test and Fix iPhone 6 WiFi Fault
According to customer's description, his iPhone 6 device has been sent to two cell phone repair shop but didn't fix well. We can see much solder flux on WiFi module, so we can judge that it has been replace several times, and the resistor near to it is also lost , the copper wire can be seen on the bottom of Wife, so we can make sure it is not the iPhone 6 WIFI module problem.
First remove the WIFI and boot device to measure the voltage of WIFI bottom board pin, we find that 14 pin has no signal voltage, it should be 1.8V. The problem comes from here. Using a digital multimeter to measure but no resistance, so we use WUXINJI bitmap to check and find it is directly through CPU, is it the bottom board wire disconnection?
It can be seen from the bitmap 10-25-1 that the iPhone 6 bottom board wire is really disconnected.
Now we have to see if there is another way, continue to look at the principle diagram Apple 6. As shown in picture 10-25-2 and 10-25-3.
This reset signal has a capacitor and a pull-up resistor. The capacitance is next to WIFI. There is no resistance in the measurement. This is hopeless, then we look at the pull-up resistor again, find it is on the back of the iPhone 6 CPU from the bitmap, and it's very close. Measuring resistance is 446, then directly solder jumper wire, install WIFI, but the icon is still gray. Then we think the WIFI may be broken. Immediately replace a new WIFI chip, Bluetooth is shown up, WIFI also appeared, the fault is fixed now!
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...
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...
Since the size of iPhone6s plus screen display is large, it's necessary to use two sets of background lights to supply power, one is provided by U4020, the other is provided by U4050. 2 sets of circuit 1) PP_LCM_BL_ANODE, PP_LCM_CAT1, PP_LCM_BL_CAT2 2) PP_LCM_BL34_ANODE, PP_LCM_BL_CAT3, PP_LCM_BL_CAT4 For PP_LCM_BL_ANODE and PP_LCM_BL34_ANODE, if one of the circuit has no voltage value, it will cause the iPhone 6s Plus screen to be half bright and half dark. For PP_LCM_CAT1, PP_LCM_BL_CAT2, PP_LCM_BL_CAT3 and PP_LCM_BL_CAT4, if one of these four circuits gets abnormal signal, it will cause the 1/4 screen to be dark. Solution: Use jumper wire to short connect PP_LCM_CAT1 and PP_LCM_BL_CAT2 or you can also connect PP_LCM_CAT3 and PP_LCM_BL_CAT4. The control signals of these two sets of backlights, one group of inductors FL4211 FL4212 FL4213 are sent to the display interface. The other group is sent to the display interface...
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