Lenovo V470 notebook computer Won't Turn On repair

Lenovo V470 notebook computer Won’t Turn On repair

Machine model: Lenovo V470

Fault phenomenon: laptop Won’t Turn On

Lenovo V470 laptop Won’t Turn On repair Figure 1.

Maintenance process: first check 51123 working conditions.

Lenovo V470 laptop Won’t Turn On repair Figure 2.

After measurement, the en signal is only 1.118v on the low side. Check the source of EC signal, which is controlled by d3601 and comes from EC (this fault is almost the same as the previous repair of dell3421), measuring EC_The rst signal is only 1.223 v.

Lenovo V470 laptop Won’t Turn On repair Figure 3.

Ecrst signal and 3v5v open signal are controlled by pure_HW_Shut down ා, remove the q2701 and d3601 boards and display them into the system normally. Check that all functions in the device manager are normal.

Lenovo V470 laptop Won’t Turn On repair Figure 4.

Lenovo V470 laptop Won’t Turn On repair Figure 5.

Because the dell421 almost had the same fault last time, it was normal after disconnecting EC reset and 3v5v EN, so I didn’t check pure_HW_Shut down ා what is the reason that the guide is pulled down.

If the same fault occurs, check the pure_HW_What is the reason for the low shutdown? Check pure_HW_There are 5 places in total.

8602, u2702 empty, 2701, 3601, 280 have disconnected q2701 and d3601, and u2701 is empty. The quantity q8602 has three poles, G and s are 0V, D is 1.223V, and q2802 three poles are 0.579v, D is 1.223V, and S pole is 0V.

Lenovo V470 laptop Won’t Turn On repair Figure 6.

Through the measurement, q2802g is obviously wrong. Disconnect r2811g or 0.579v, turn on q2802 DS pole OverLoad, DG is 1109, normal NPN should be more than 500 DS, DG is OverLoad, there are the same bad boards on hand for comparison.

Lenovo V470 laptop Won’t Turn On repair Figure 7.

Lenovo V470 laptop Won’t Turn On repair figure 8.

Pure after q2802 replacement_HW_Shutdown ා has been normal to 3.3V.

Summary:

The fault is that q2802 is broken, causing ecrst and 3V_5V_It’s OK to not install no power on and q2802 due to abnormal en. Several diode value between pin and diode value are marked on the removed triode.