Lenovo 15ISK NM-A711 Notebook Does Not Turn On Repair

 

Laptop Model : Lenovo 15ISK NM-A711

 

Fault: The notebook does not power on, and there is no response when pressing the power button.

 

Maintenance process:

 

When disassembling the machine, it was detected that there was a 3.3V short circuit of 2 ohms. When the power was turned on, the temperature could not be detected, and the 3.3V voltage burned 2A. When looking with a thermal imager, only redness near the PL600 was seen.

 

I thought the south bridge was short-circuited, but I measured that the capacitors below the south bridge were not short-circuited, and the capacitors above the bridge were not short-circuited. 

    I thought the south bridge was burned. If the other bridges were burned, they would be obviously hot.

　　The vinyl bridge is hard to replace and the bridge is very expensive. I was ready to give up, but it still felt weird. I used thermal imaging again to put my finger on the South Bridge crystal and clearly saw that the finger part was not red. 

    Could it be that the bridge was broken? Even if the 3.3V inductor is removed, the burn is still not obvious, and the 3.3V power supply chip is also the same. The thermal imaging is just this one, and you can't tell which one it is

    Fumigated it with rosin and then burned it. Sure enough, there was a melted part. After a closer look, it turned out that the 3.3V output filter capacitor was short-circuited. The key is that this kind of capacitor is generally used for 20V filter capacitors and rarely breaks, so I didn’t use it. 

    After thinking about it above, I removed it and tested it, and it turned out that it was short-circuited. The 3.3V short-circuit was eliminated, and it could be turned on after powering on again.

 

Happy Repairing !