Released 2018, November
Version: SM-A920F/DS (Global)
Drop damage caused the auto focus function failure, cannot scan the QR code.
Replace the rear camera module and tested twice, the issue is still unresolved.
Since we have tested with another camera module, the issue stay unresolved.
The issue should be caused by the motherboard.
And we can see the image when take pictures, so the power supply and MIPI signal rails should be also OK.
Then we can target the AF (autofocus) power supply rail as the suspicious defective rail.
Repair Process
First, we should find out which rear camera with issue
Cover the rear cameras with finger, then test and find out the 3rd camera (main camera) is responsible for scanning the QR code.
Besides that, we can choose the different magnification times (0.5X / 1X / 2X ) to test again, to see if the focus function works in different magnification status.
Testing result
Ø 0.5X AF OK
Ø 1 X AF NG
Ø 2 X AF OK
The disassemble the motherboard, and check the rear cameras’ related connectors and components carefully.
We can find, around the 1st camera (the ultra wide camera) connector there are 5 LDO chips.
The 5 LDO chips, provide power for the ultra wide camera and telephoto camera.
Also around the 4th camera (Depth camera) connector, there are 4 LDO chips
The 4 LDO chips, provide power for the Main camera and Depth camera.
Check the connection between the LDO output sides and the Main camera connector.
We find the 4th LDO connected with the Main camera to provide power.
And the power on the 1st pin of Main camera connector, also provided to the Depth camera. So it should be OK.
Based on previous repair experience, there do have some cases which LDO damage cause the camera auto focus function failure. So there’s a high chance the issue is caused by the LDO chip poor soldering or get damaged.
Get the LDO replaced with a new one, then the issue get resolved.
