Before fixing iPhone 6s boot failure, you have to check if the iPhone device is broken or deformed. Open the iPhone screen to check the traces of water corrosion, the battery resistance is checked with normal value, then test the device with multimeter( 2A am multimeter is recommended ) directly up voltage to 1.8A, it belongs to the high current system.
Tear down all the accessories and starting with a single iPhone 6S motherboard, the result is the same, so you can be sure that the accessories or parts are ok. Before we fixed a lot of large current cell phone devices, power on and directly measure value, making sound is basically the components on VCC main power supply get problem, but the situation of current up to 1.8A is still relatively rare. After determining the measurement, we can confirm the problem is from VCC circuit, for big current device, you can use rosin with electric solder iron, apply rosin on the solder iron and work on VCC main circuit components, it will produce white smoke, power on again, you can see Q2300 charging switch tube quickly shine. The part is shown in picture 10-1-1.
This will make people think that the booting problem is caused by this parts, according to our experience, it's not caused here.
Two circuit power supply is shown in picture 1-1-2.
Because this component focuses on B+ and VCC power supply, so it's heating firstly, but it can be determined that it's not bad, for 6S 1.8V device, you can directly focus the problem on backlight part. As shown in picture 10-1-3, the backlight part is easy to burn out.
Open the iPhone CPU shield (setting spiral hot air gun 260 degrees can easily take off, avoid high temperature, so as to avoid CPU solder explosion), we find the traces of components are burn out on the two backlight diode and C4023, it is best to pack first before processing elements near the CPU. As shown in picture 1-1-4.
Disassemble two diode and a capacitor and power on again is normal, deal with the solder pad with high low temperature solder. you should be gentle when handling it since the pad is easy to fall off. Replacing the new components, reboot and test, every function is normal now. As shown in picture 1-1-5.
Note: If the diode is installed in the reverse will appear large current phenomenon, after the replacement, you can test again by solder iron with rosin so that will be more intuitive to see whether it is installed, C4023 capacitor must be installed, otherwise it is easy to burn the iPhone backlight IC.
This iPhone 6S problem is solved after replacing two diodes and capacitor C4023. Some of the backlight IC and backlight inductance get yellow, which will be required to be replaced. 6S backlight parts are easy to be broken, and the components are all covered with glue. When you remove it, don't be impatient. It will be convenient for the following work after the glue is removed.
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...
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...
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