Lenovo G400S LA-9910P Shuts Down In About 30 Seconds

 

Laptop Model: Lenovo G400S

Motherboard ID: LA-9910P

Problem : Shuts Down In About 30 Seconds

 

　　Fault phenomenon: The phone can be turned on normally when triggered. During the process of entering the system, it loses power and shuts down. After power failure and shutdown, it can be triggered to turn on again, and it will automatically shut down again when it is about to enter the system.

 

　　Maintenance process: At first I thought it was caused by high temperature, but I didn't feel overheating when I touched the copper pipe. So, I took out the motherboard and tested it with the bare board, and it was the same. I counted silently in my mind before shutting down the phone in about 33 or 34 seconds. 

 

I checked the PROCHOT# and THERMTRIP# signals of the CPU over-temperature module and found nothing abnormal. So searched for the CPU temperature module (THERMAL) in the drawing, it found that there were two signals CATERR# and PECI.

H-CATERR# is only connected to one test point externally and not to other places. The PECI signal is connected to EC pin 118 through a 43 ohm resistor. I used a magnifying glass to observe pin 118 of the EC.

There seemed to be a black spot on this pin. I poked it with a test pen and found the fault point. It was the disconnection of the PECI signal that caused poor communication between the CPU and EC, so I repaired the fault by patching the line.

Happy Repairing !