Saturday, November 3, 2012

USB Port not working on Motherboard

USB device are not getting detected.USB not recognized.

On the motherboard there are on-board USB ports.
In these ports a pen drive,a USB mouse or USB keyboard can be connected.

But if there is a problem with USB port the USB devices will not get detected and it will not work.


1) No +5 Volt supply on USB connector Pin.

2) Issue with frequency.

3) A faulty ICH South bridge.


For reason 1 Apply jumper from any fusible resistor where +5 Voltages are received on first pin of USB connector.

Please Note:--- A USB port has 4 soldered pin on opposite side of motherboard.Out of these 4 pins,the first one is square pin.And that square pin receives +5 Volt.If you test the first square pin of USB connector port and there is no +5 volt then USB will not work.Any port needs power to function.So if power supply is zero then it will not work,even though port looks good.
Beside every port,in most of cases the volt passes through fusible resistor.
So if USB port is not receiving +5 volts,then connect a jumper from Any other port,like LPT port or from Com port or from VGA ports +5 Volts fusible resistor and these will make USB port working again.

FOR Motherboard USB Connector Pin details

For reason 2,the frequency has to be checked.USB port gets frequency from Clock Synthesizer.So get the datasheet of Clock Synthesizer chip and in that check the Frequency Pin of clock synthesizer pin.The USB port needs either 48Mhz or 24Mhz frequency to operate.

If you test the clock Synthesizer pin and there is no frequency on that pin,then USB port will not function,even it is receiving +5 Volt on Power supply Square pin.So in that case Clock synthesizer chip has to be replaced.

So both voltage and frequency re required to make the USB port operate properly.


For reason 3,if the power supply on first square pin is OK,if the correct frequency is received on clock synthesizer pin and still the USB port is not functioning right,then problem is related to faulty ICH,also called southbridge.

The USB port is directly controlled by ICH.
On some cases you will even notice ICH getting overheated.So that will also give a bit of indication.
First try heat the ICH using Hot air gun.The solder balls underneath the ICH chip set gets bit dried up and looses contact with motherboard.So bit of re-heating the ICH chip to its heat temperature will help to get the loose solder balls melt and get re-connected to the motherboard and USB starts working.

But if that is not helping,then replacing ICH or Reballing ICH chip set will help.


These details will help.

For motherboard related issues and solution.Go through the troubleshooting help links provided below:------

Troubleshoot Dead Motherboard

Troubleshooting NO Display Problem on Motherboard

Troubleshooting CPU Overheating Problem on Motherboard

Desktop Motherboard Cpu Fan Connector

No SMPS Power Good on Super I/O Chip

MCH OR ICH Heating on Motherboard

Desktop Automatically Turns ON

Motherboard Immediately Restarts

MotherBoard Will Not Start With 4-Pin ATX power connected

PC Motherboard System Hangs Or Very Slow

Colors Missing On Display