Troubleshoot: iPhone 6S receiver failure (no voice)

Last week, we received an iPhone 6S need to repair, the problem is that the iPhone receiver is failed to work,  the iPhone 6S receiver has no voice when calling. After testing, the iPhone receiver is not working, but the iPhone speaker works good. Now, we need to troubleshoot it.

There are several reasons will cause iPhone receiver failure:

 
- iPhone receiver, 
- Receiver flex cable
- Receiver circuit 
- iPhone audio IC problem

How to troubleshoot? 

First , replace the receiver and flex cable, and then test the iPhone 6S, but the failure still exist.

Use digital multimeter to measure the diode data of receiver signal 1 pin and 3 pin that on the connector J3100, the data measured are normal.

Check iPhone schematic diagram via WUXINJI Dongle, we know that the 1 pin and 3 pin of J3100 are through capacitor FL3153 and FL3154 to iPhone audio IC U3500, their diode data are normal, which means the capacitor FL3153 and FL3154 are normal.

After excluding the cause of the peripheral components，we start to check U3500. Take out the iPhone motherboard, we found the U3500 has been replaced before by other repair man,  the several filter capacitors around it has been removed, and there is a power supply IC of NFC also has been removed.

Now, we need to fix iPhone receiver failure, directly replace the iPhone audio IC U3500. After replacement, connect iPhone 6S to the DC power supply, the trigger current jumps from 0 to 80mA, it's been circulating like this.

The replacement IC has been soldered well, the iPhone CPU didn't been blown by QUICK 861DW hot air rework station. Remove the iPhone audio IC, now the current is back to normal, so we confirmed that it's the problem of the iPhone audio IC. Replace it with new iPhone audio IC,now the data tested is normal.

Finally, assemble the iPhone 6S, power on iPhone, entering the IOS,  and then test the iPhone receiver, now the iPhone receiver is working properly. The tourble has been fixed!