A customer sent us an iPhone 6S
motherboard, the problem is that the iPhone 6S is short circuit after booting.
After we received the iPhone 6S
motherboard, it looks good and never been repaired.
Connect iPhone motherboard to the DPS DC power supply, the current of the beginning tested is
20mA, it's normal.
When the current jumps to 40mA, which means
the iPhone power and CPU starts to work. When the current jumps to 10.6mA,
which mean the upper was opened.
When the current jumps to 70.8mA, which
means the iPhone Nand flash starts to work. When the current jumps to
100mA, which means the CPU starts the I2C data bus, at this time, the iPhone
display power IC start working, the Apple LOGO will appear on the iPhone
display screen, and then the iPhone backlight start to work. At this time, the
current is usually around 300mA.
When the Apple logo appears, the current on
the DC power supply screen is constantly jumping，because the iPhone baseband
and iPhone WiFi are being started. After the iPhone screen is lit, the current
will jump back to 300mA from 500mA.
However, when the current jumps up the
second time, the iPhone motherboard is short circuit and turned off. Our
preliminary judgment is that the amplifier has a problem.
First to check whether the power supply of
amplifier is normal, after testing, every power supply of amplifier is good.
Seems it's complicated, but after thinking,
we know that the iPhone amplifier IC and iPhone WIFI IC are the most power consumption parts.
Connect iPhone motherboard to DC power
supply to boot it, after few second, the WIFI is overheating, the problem was
found.
Heat iPhone WIFI IC by QUICK 861DW hot air rework station, and then use Titanium Alloy Tweezers to remove the iPhone WIFI IC. Now, measure
it again, the current is normal, and no short-circuit phenomenon.
Install the new iPhone WIFI IC, remove the
iPhone Nand flash, and then use JC Pro1000S to unbind
the WIFI.
Finally, install the iPhone 6S, and test
it, now the iPhone works properly.
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