We received an iPhone X needs to be repaired, the problem is that the iPhone X voltage is unstable, it jumps repeatedly from 0mA to 50mA, and it is different from the normal booting current. Here, you can get best solution to repair it.
when we received the iPhone X, we carefully remove the iPhone X motherboard by phone opening tools, and then we 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 VC890D 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 the CPU power supply! As shown in iPhone X schemtic diagram 14-3-1 , there are three ways of power supply, not only directly into the
CPU, but also through the small resistance or inductance into the CPU, the
three voltage are PP1V2_SOC, PP0V8_SOC_FIXED_S1, PP1V8_IO.
Testing
the 3 power supply one by one, when the FL1092 inductor of PP1V8_IO is
measured, one end is 1.8V while the other end is 0V.
Testing
the end without voltage to the ground dipole value is 490, the normal is about
280. Then testing the inductor's noumenon value is very large, indicating the
iPhone X inductor is damaged.
Put iPhone X motherboard on the iPhone X PCB Fixture holder, and then replace a new inductor. After finish that, we measure the iPhone X again, now the diode data is back to normal. The repairs end!
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