How To Solve Usb Port Not Working Problem In Laptop Motherboard

The trick to solve LENOVO G50 motherboard part no. - nm-a272 All USB not working Problem.

Problem - LENOVO G50 motherboard part no - nm-a272 All USB port not working Problem.
Laptex Family Member
Ankur Khandelwal
From Rajasthan
nm-a272 usb port not working problem
Troubleshooting - As per Discussion in LAPTEX-Laptop Repairing Training Course if USB not working then need to check the working of the USB IC. 

The basic Working philosophy of any IC, in general, is that:-

1) Power Supply (VCC, VDD, etc.)
2) Enabling Supply (EN, CS, etc.)
3) Output Supply (Vout, ALW, PCU, etc.)

This Lenovo G50 model with SKU part no. nm-a272 was already tampered by some other technician for the same problem. Also, he changed the SIO or controller IO but the problem not solved.

NOTE - No need to change SIO in this case, as a USB communication is directly related to the HUB, PCH or Chipset so the doubt should go to the enabling input from PCH and not on SIO as per discussion in the online laptop repairing training module.

Steps to solve this problem

1) I checked all the USB jack 5 VOLT VCC which is needed for USB to work was missing. First I changed this IC but the problem not solved.

2) Then i checked the requirement of the USB power IC. It's 5 VOLT input was ok but output voltage not coming.
usb power ic
3) I Checked IC ENABLE volts on pin no 4, instead of 3.3 volts it was dropped to 1.67 volts. It means IC not ENABLE to provide output.

4) Then, I traced the ENABLING supply and found it was coming from PCH. It was confirmed that in the track path it was getting dropped somewhere. So, I decided to put a jumper wire from the output of PCH to the enabling input of the USB IC.

5) I removed the USB power ICs and made a direct connection to the ENABLE pin via a jumper. The
problem was solved and USB ports working normally.


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