The iPhone 6 is very old version, and it's reasonable to have some problems. Here is an iPhone 6 with not turning on problem and no backlight. Luckily, we can fix it, and here is the fixed details.
Use phone opening tools to disassemble the iPhone, and take out the iPhone motherboard to the oberve it, we found that the top right corner screw column of the
iPhone CPU is missing, the iPhone motherboard has been dug and welded jumper
wire.
Connect iPhone motherboard to the DPS DC power supply to check the current condition, we found
that the iPhone current was above 200mA, then dropped and stayed around 150mA.
According to the iPhone boot current working process, we analyze that the
iPhone isn't turned on when the current was above 200mA, this failure is
usually caused by iPhone display and backlight circuit. Use digital multimeter
to measure the grounding resistance value of the display and backlight circuit.
The resistance value measured is normal, so
we replace the iPhone display IC, but the problem still the same after
replacement. Now, we need to replace the iPhone backlight IC, after
replacement, we found the iPhone boot current jumps normally. Install the
iPhone display assembly and test it, the iPhone can be turned on, and the
backlight also is normal. However, when the iPhone came to unlock the
interface, the iPhone display screen suddenly became dark and then completely
black, the iPhone backlight didn't work anymore, and the iPhone boot current
stays at the same value as before.
Seems it's the iPhone backlight problem,
and it causes iPhone can't enter the IOS smoothly. Replace the several iPhone
backlight ICs, but it is still not working. Measuring the voltage with digital multimeter, the working condition of the iPhone
backlight all is normal, only the voltage of backlight boost 17V are not up to
the normal value. Check iPhone by the light, we can see that the iPhone screen
stuck in the boot interface.
Replacing the iPhone backlight IC is useless, so we are going to replace the
iPhone backlight IC, iPhone diode tube and inductors.
After replacement, the iPhone was normal at
first, but it didn't work the second time it turned on. Check iPhone schematic
diagram via WUXINJI Dongle, we found there are many wires under the
screw column, which includes the wire of the iPhone backlight circuit.
Put iPhone under the Stereo Zoom Microscope, dig the iPhone motherboard，we found the
cathode wire of iPhone backlight is cracked, solder the jumper wire on it, and
then apply some green UV oil.
Connect iPhone motherboard to DC power
supply to test it, now the data tested is normal.
Insall the iPhone motherboard, connect iPhone battery and iPhone display assembly, and then press the iPhone power button, the white Apple logo appears as usual, after few seconds, the iPhone is enter the IOS systems smoothly.
Using it for 1 day, the iPhone 6 is working properly, and all functions tested are normal.
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