The iPhone 6 plus was fell into before, it has been replace two WIFI chip, but both failed, WIFI still cannot turn on, then measured the relevant work conditions of the WIFI circuit, there is nothing wrong. The fault interface of WIFI as shown in picture 4-8-1 .
The
customer has changed two WIFI chips, and has measured the main working
conditions: WIFI two power supply, WIFI-32K clock. So we enter into the first
step of repairs directly: Measuring the WIFI circuit of PCIE communication bus,
we find the 2 pin of capacitor C0704 to CPU ground value is low, the actual
measured value is 221, normal motherboard resistance is 560. Thus, we can judge the problem is from CPU . As shown in
picture 4-8-2
The
position of the capacitor C0704 is shown in picture 4-8-3
According
to the maintenance experience we can judge like this: Generally if the ground
value is small, and at the same time it's leading to CPU, It is unable to
repair, but we still have a try.
1.
Remove the CPU and clean the pad;
2.
Remove the glue from the middle of the CPU and repair the solder.
3.
Then soldering the lower CPU with reballingstencil. As shown in picture 4-8-4 .
4.
Filling the tin and soldering it on the motherboard CPU, as shown in picture 4-8-5 .
5.
Install the upper cover temporary storage after reballing, it shows normal and
can reboot normally after cooling device to measure, but when measuring the
C0704 capacitor 2 pin, we found that the failure is still the same as before,
and the ground value is same as before.
Summary:
If you meet the situation, ground value is obviously small and it also
connected to the CPU internal, there is no need to remove CPU. To solve the
fault you must replace the full suite.
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