Lenovo ThinkPad T460 notebook without charging repair

Machine model: Lenovo ThinkPad T460

Main board version number: NM-A581

Fault: The notebook is not charged, and the screen flashes.

Maintenance process:

A Lenovo ThinkPad T460 notebook, plug in the charger to lock the frequency to 0.38Ghz, the running card is slow, the screen flashes, the lower right corner indicates that the power supply and battery are constantly switching, and the single battery is running normally. This machine is used to repair Previously repaired machine. Visual inspection is used to disassemble the machine, and the welding marks of the charging circuit are extensively repaired. EC has changed it. It is preliminarily judged that frequency locking and no charging are caused by the same fault point.

From the beginning of charging, the measured standby current does not return to zero, 0.022A is slightly too large, and it normally returns to zero after 3 seconds at 0.014a. Check the standby VCC, and the linear VL5 and U14 VCC3SW of PU201 are turned off manually, respectively, and there is no change. Remove PQ20, verify that it is caused by back-end VINT20, and diode value is normal.

Lenovo ThinkPad T460 notebook without charging repair Figure 1.

Check VINT20, whether the main PJ PL is completely turned off or not, continue to check VINT20, and the current will return to zero after turning off PR49.

Lenovo ThinkPad T460 notebook without charging repair Figure 2.

Lenovo ThinkPad T460 notebook without charging repair Figure 3.

Check the back end of PR49 to find DOCK_CONSUMP, call diode value 400 Euros, and continue to catch up with the docking station.

Lenovo ThinkPad T460 notebook without charging repair Figure 4.
After alcohol cleaning with brush,Diode value is normal. Installation test, all functions are normal, troubleshooting and maintenance are over.