Lenovo G40-30 notebook cannot be started for repair due to water ingress

Lenovo G40-30 notebook cannot be started for repair due to water ingress

Machine model: Lenovo G40-30

Version number: NM-A311 solo display

Lenovo G40-30 notebook cannot be started for repair due to water ingress Figure 1.

Lenovo G40-30 notebook cannot be started for repair due to water ingress Figure 2.

Malfunction: standby 0.08 Switch has no response.

Maintenance process:water damage was found on the shell after disassembling the machine, and corrode was found at 5V, while corrode water damage was not found at other parts. After a simple cleaning, the fault remains the same. The measured 3V is normal, 5V is abnormal, and the measured value is 0.75V.

Lenovo G40-30 notebook cannot be started for repair due to water ingress Figure 3.

Lenovo G40-30 notebook cannot be started for repair due to water ingress Figure 4.

Disconnect the 5V isolation point and measure the front end 0V(Inductor end) and the back end 0.75V.

Lenovo G40-30 notebook cannot be started for repair due to water ingress Figure 5.

Generally speaking, the level after disconnecting the isolation point is 0. If you want to solve the level after first, check schematic. One by one, I went to disconnect the chips, and I checked for a long time without any results. If you have the same motherboard display on your hand, a fault of 0.23 does not show CPU failure,board swap. It’s a whim to disconnect this 5V isolation point for measurement, and find that the front end of the isolation point is 5V and the back end is 0.75V.

Lenovo G40-30 notebook cannot be started for repair due to water ingress Figure 6.

Lenovo G40-30 notebook cannot be started for repair due to water ingress Figure 7.

Then replace the 5V standby chip, connect all disconnected isolation points, install the chip, stand by 0.02,switch 0.4,0.5, and the screen connection is on.

Lenovo G40-30 notebook cannot be started for repair due to water ingress Figure 8.

Summary:
The fault of the machine is very simple, except that the 5V chip corrode is damaged, resulting in no 5V output, but it took a detour because of the wonderful design of the motherboard. If my first thought was to fix the front end and then the back end, it would be a second kill machine.

Note: The current of this machine’s integrated display booting up is about 0.2 or so, and the independent display current is 0.45-0.5.