Repair of DELL Vostro 5470 notebook adapter without power on or charging

After dismantling Q32, it was found that the voltage was still 1.4V Keep looking for the next level circuit along the 3.3V_ALW_ON, and find PQ12. The air gun blew it down, and found an NMOS of CJ2306 to solder it on. Test again that the voltage is normal.

Machine model: DELL Vostro 5470 notebook

Failure: The notebook adapter does not power on or charge.

Maintenance process:

A DELL 5470 fault machine, the notebook suddenly does not turn on, the plug-in adapter does not turn on and does not charge, but the battery can turn on.

Plug in the adapter power supply, the charging light flashes and then goes out. The multimeter checks that the battery has no electricity, and the output of the charging chip BQ737 is only about 3.4V When the charging chip is replaced, the failure remains the same, and the machine can’t be turned on or charged.

Open the drawing to check the circuit, and find that when only the battery interface is used for power supply, the 3.3V voltage of G1 short circuit test point is normal, and it can be turned on normally by short circuit with tweezers. Once the adapter is plugged in, it will be gone.

Maintenance of DELL Vostro 5470 notebook adapter without power on or charging Figure 1

When ACAV_IN has voltage (that is, when the adapter is plugged in), Q33 turns on and pulls down. At this time, the POWER_SW_IN0# should be pulled up to 3.3V from R279, but +3.3V_ALW is not generated, and +3.3V_ALW is controlled by 3.3V_ALW_ON. At this time, the multimeter measures that the voltage here is only about 1.4V First, it is suspected that Q32A is damaged and slightly turned on.