Dell N4050(10315-1) Laptop Does Not Turn On

Laptop model: Dell N4050

Version number 10315-1

Fault: Dead

Repair Process:

Standby for 0.01, no response when pressing the switch. Measure the switch voltage to 3.1V, and it can be pulled down when pressing the switch. Based on the maintenance method of first soft and then hard, we first measure the BIOS chip and read the data waveform during standby.

After flashing the BIOS, it didn't work. I wanted to find something missing, but it seemed hopeless. Open the drawing and find that the pin from the switch to EC is GPIO6.

When measuring, it can be pulled down normally when the switch is pressed. Looking at the PWRBTN signal from the EC to the bridge, the measured EC pin 117 is always low.

You have to determine whether it is an EC problem or a bridge problem. The EC pin is not easy to pick up, so first look at the standby conditions of the bridge! Starting from the universal RSMRST measurement, a fault is found and RSMRST#_KBC is low level.

 Then it’s easy, don’t worry about the PWRBTN signal, fix the RSMRST first (this drawing has the timing chart RSMRST is issued before pressing the switch). After reading the BIOS waveform, the RSMRST pin is not pulled high, and it is normal to measure the LID signal first.

        Then look for the AC_IN signal. The AC_IN signal of this model is as shown in the figure:

The voltage is wrong, it should be 3.3V normally. The ACIN signal is controlled by AC_IN# through PQ4006.

The G-level voltage of PQ4006 is 0.9V, which should be 0V normally. I dismantled the PQ4006 and verified it, and found a big problem. The G-level pin was actually 3.3V. It seems that the AC_IN# signal of the charging chip was not sent out correctly.

The 20-pin VCC of PU4005 is 19V, and the 6-pin ACDET is 2.6V. They are both normal. Try changing the charging chip! After replacing it, the problem still persists. 

     The voltage of the charging inductor was measured to reach 19V, and the PU4003 DS was short-circuited. After removing the PU4003 DS pin, it was still short-circuited.

  After removing the PU4004, it finally became normal. It can be triggered by pressing the switch. After replacing the PU4004, it was OK immediately.

Happy Repairing !!