Redmi Note 9 Pro cannot be charged

Machine model:Redmi Note 9 Pro

Fault phenomenon:Redmi Note 9 Pro can not be charged. The new charging connector small board and FPC were replaced before.

Redmi Note 9 Pro cannot be charged Figure 1.

Maintenance process: get the mobile phone, power on and plug in the charging wire for test. It is found that the mobile phone has no charging current and the charging icon is not displayed on the screen.Take apart the back case of the mobile phone and measure that the charging connector FPC on the mainboard has 5V VCC input, which indicates that the failure of charging has nothing to do with the charging connector small board and FPC. It can be determined that there is something wrong with the motherboard.

Redmi Note 9 Pro cannot be charged Figure 2.

Check Boardview, find 5V input point through charging connector BTB connector, and find that it is connected to charging Current protection tube q6501 and q5501.

Redmi Note 9 Pro cannot be charged Figure 3.

So we took out the main board, cut the shielding cover, and observed it under a microscope. It was found that The solder tin extruded was found in the charging Current protection tube q6501. After measurement, it was found that the Current protection tube q6501 had been broken down.

Redmi Note 9 Pro cannot be charged Figure 4.

Check the schematic and MOSFET data of Xinzhizao Soft software and know that this is an n-channel MOSFET. Find a good n-channel MOS and replace the bad MOSFET.

Redmi Note 9 Pro cannot be charged Figure 5.

Redmi Note 9 Pro cannot be charged Figure 6.

Install the motherboard into the machine and plug lighting cable into the machine for testing. The screen shows the fast charging mode. The charging current returns to normal and the fault is repaired perfectly. The Redmi note 9 Pro can not be charged. The maintenance is over.