The Mi 11 camera not working issue repair.
Model: Xiaomi Mi 11
Released: 2021, January 01
Defect Phenomenon
Besides the camera function issue, the phone can work normally. Turn on the camera to test, the screen will turn black for 1-2 seconds, then appear the camera button and exits automatically.
Troubleshooting
The camera turns off automatically is normally caused by either the power supply or the I2C bus.
So let’s find out the camera power IC U7306 first, the location of U7306 as below
Based on the repair experience, this chip with higher failure rate, so let’s use the hot air gun to resolder the chip directly.
After that, test the camera function again. Still does not work…
So let’s go to the camera connector and measure the diode values on the camera connectors J7202 and J6600.
After measuring the diode value, let’s check the voltage on the I2C bus.
The I2C bus for the rear camera and the front camera as below
Rear Camera
- CCI_I2C1_SDA
- CCI_I2C1_SCL
Front Camera
- CCI_I2C0_SDA
- CCI_I2C0_SCL
Both the two I2C buses with no voltage can be measured. Carefully check the schematic again, the power supply for these I2C buses is from CAM_IO_1P8.
And the CAM_IO_1P8 also comes from the U7306.
The issue comes back to the chip again, but we’ve resoldered it before. So there is a very low chance it’s caused by the chip pseudo soldering or damage.
Let’s check the working conditions for the U7306, we found there’s an I2C bus for this chip
Let’s track the I2C bus, maybe it’s this I2C bus with the problem caused U7306 working station cannot be satisfied. After checking we can see there are two pull-up resistors and the two signals
- APPS_I2C_SDA
- APPS_I2C_SCL
are out from the CPU directly.
There are two resistors R3201 and R3202.
Measure the diode value with the multimeter on the side which connects with the CPU, it’s grounded!
This means the short comes from the CPU. And we should resolder the CPU to have a try.
After reballing and soldering the CPU back, assemble the phone to test.
The camera function works well, and all the other functions are also OK. Issue get resolved by CPU reballing perfectly.
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