DELL Vostro 5470 laptop no booting is not repair

Machine model: DELL Vostro 5470

Fault: Notebook adapter no booting is not charged.

Maintenance process:

A DELL 5470 fault machine,notebookno booting suddenly, plug in adapter no booting without charging, but the battery can be turned on.

Plug in the adapter power supply, and the charging light will go out in a flash.multimeter checks that the battery is dead, and the output of the charging chip BQ737 is only 3.4V or so. If the charging chip is replaced, the fault still remains, but it can’t be turned on or charged.

Open the drawing inspection circuit, and find that when only the battery interface VCC is used, the test point 3.3V VCC of G1 Short circuit is normal, and the tweezers Short circuit can be used to start the machine normally, but once the adapter is plugged in, it will be gone.

DELL Vostro 5470 laptop no booting is not charged for repair Figure 1.

When ACAV_IN has VCC(that is, when the adapter is plugged in), Q32A is turned on and pulled low. At this time, POWER_SW_IN0# should be pulled up from R279 to 3.3V, but +3.3V_ALW is not generated, and +3.3V_ALW is controlled by 3.3V_ALW_ON. At this time,multimeter measures that VCC only exists here.

DELL Vostro 5470 laptop no booting is not charged for repair Figure 2.

After removing Q32, it was found that VCC was still 1.4V Continue to look for the next level circuit along 3.3V_ALW_ON, find PQ12,SMD REWORK STATION blew down, found an NMOS solder of CJ2306, and tested that VCC was normal again.