We are going to repair iPhone 5S audio part
issues in this article. The audio part is made up of iPhone audio IC-U21 and ringtone amplification IC-U22.
1. If there is no any voice on iPhone 5S,
first we need to check each power supply on U21 circuit whether they are
normal. If there is a voltage is abnormal, we need to handle it first; if all
voltage works normally, then re-install or replace the U21.
2. If the receiver has no sound （normal call
mode）, replace the receiver and flex cable, check the channel of the
receiver, check short connection for FL51 and FL 51, re-install or replace
audio U21.
3. If your voice can't be heard （normal call
mode), replace the iPhone tail plug flex cable, check the microphone channel,
check short connection FL49, check if C222 and C333 are dropped or replaced,
re-install or replace audio U21. Furthermore, after make the phone call, please
use Fluke 15B+ Digital Multimeter to
measure the power supply on microscope to check whether there is a 3V, if not,
we can solder a jump wire from the iPhone Nand flash power supply PP3V0_NAND to FL49
4. If both the receiver and the transmitter
have no sound， test the recording to see if it's normal，and whether
the receiver has the sound （receiver mode）. If the receiver and the microphone channel are not detected by the
recording, check the short connection FL49, FL51 and FL52, check if C222 and
C333 are dropped or replaced. Re-install or replace U21.
5. If the recording is normal, but there is
no sound on the phone call, this situation is usually caused by CPU virtual
welding, re-install iPhone baseband CPU.
6. If the sound is normal when in phone
call, but there is no sound in speaker mode, check iPhone speaker, replace
light sensor flex cable, check speaker receiver channel, check short connection
FL48, check if C55 and C61 are dropped or replaced, re-install or replace audio
U21.
7. Speaker no sound and no ringtone, check
if C335 has a voltage of about 4V, check short connection L4, check short
connection FL6 and FL9.
Tips: you can check iPhone schematic
diagram on WUXINJI Dongle.
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