We got a iPhone 6S Plus to repair, the iPhone audio has some problem. But now we can't make sure what caused this, we need to check it first.
Connect iPhone to DC power supply and test the original iPhone audio IC, the current is normal. And when we replace the new audio IC to test, it shows large current. So now we can judged that the original audio IC is good.
Connect
the iPhone device to check, it is not available for recording but the ringtone
is normal. After disassembly, we find that large audio was not replaced before,
first we are going to clean the iPhone motherboard.
The electric current is normal when booting, the resistance measurement of
U3500 M7 pin is on the ground. the point is the main power
supply of PP_VCC_MAIN, if it is grounded, it will certainly clamp
large current, so once again when we pinch, large current is not there. As
shown in picture 8-6-1 .
Remove
the shielding cap to measure the capacitors C3603 and C3601 near M7, we also
found that the capacitance is measured to ground. Remove these two capacitors
to measure U3500's M7 pin and C3603, C3601 resistance is infinite, and now it
can be sure that the wire is broken. Measuring M7 pin and capacitor is interlinked,
solder the jumper wire from the capacitor C3603 to the nearest
PP_VCC_MAIN. From the picture 8-6-2 , we can see that
the point of which more convenient to borrow power is the capacitor C4020.
Then apply UV green oil to fix and insulated,
the resistance of M7 is returned to normal, and we do the clamping test again,
the current is normal, so we install the iPhone 6S Plus to test functions, all is normal. The iPhone 6S Plus has been repaired here!
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