Saturday, November 3, 2012

Ethernet LAN problem on Motherboard

You will notice Problems like:---

  • NO LAN ports connectivity.
  • Internet connectivity loss.
  • Task-bar shows connected,but No network Access.
  • internet not working.

There problem can be either related to software or hardware.
So first confirm that all LAN software is installed properly, to make the Ethernet work properly.
Once you are confirmed that LAN drivers & software is clear and issue is not software related. Then for hardware related issues, the troubleshooting is as follows: -----

1) Test the VCC voltage on LAN chip. The VCC voltages are required power supply voltage to function the chip. If VCC voltages are not received, then chip will not operate. Suppose if LAN chip needs 12 volt VCC to operate or 5 volt VCC to operate and that is not received, then you can apply jumper from another 12 volt or 5 volt source and connect to LAN chip  VCC pin and these will make the chip function.

2) Not in all motherboards, but on some motherboards there is power supply regular present near the LAN codec chip. The required voltage comes to the LAN chip via these regulator or mosfet. If in case these regulator or mosfet is present then check the voltage to the output pin of mosfet or regulator. Please note minimum voltage out should be at least 1.2 volt. If the voltage out is less that 1.2 volt, then test IN voltages on mosfet or regulator. If IN volt is more then 1.2 but volt out is less then 1.2 volt then particular power supply mosfet or regulator is faulty and needs to be replaced. You will also notice that these components getting overheated (not always but mostly).

3) Every IC chip needs particular frequency to function. To generate this frequency there is a frequency generating RTC crystal connected near the chip. If the chip itself is capable of generating required frequency then RTC is not required. So the RTC is optional and only required if IC chip is not able to generate required frequency. On some motherboard there is 25 Mhz RTC near LAN chip. So if on your board there is 25 Mhz RTC, then check its frequency with frequency testing meter. Please note frequency cannot be tested by normal voltmeter or multitester. The frequency is measured in hertz( HZ).Test the out pin of RTC.The RTC frequency can be + or _ 10 compared to actual frequency value of 25 Mhz.So if the frequency shows 14 or 15 Mhz then its ok and if it shows 33 or 35 Mhz then also RTC is ok.

4) If in case the VCC voltages are correct, the power supply mosfet or regulator near chip are ok and Frequency is also tested ok then the problem is with LAN chip. Its receiving correct Volt-IN voltages but the volt out from chip is not correct and in that case the LAN chip has to be replaced (Not always but mostly on such cases the LAN chip will overheat).

In case of BGA LAN chips it cannot be replaced,the success rate is very less.In that case you can use external LAN cards.These LAN cards fit to PCI slot on motherboard.

If the LAN drivers are ok,but no LAN is getting operated externally by LAN card or by on-board LAN then fault is related to ICH also called as South bridge.The LAN is controlled directly by ICH.

To troubleshoot ICH,see ICH overheating issues in the Link mentioned below:---

MCH OR ICH Heating on Motherboard

These details will help.

For more help,in troubleshooting motherboard related issues,go through the list of help links:----

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

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

USB Port not working on Motherboard

Motherboard USB Connector Pin details

PS2 Port Not Working On Motherboard

Motherboard HDD not getting Detected

Fix For BIOS Corrupt


Faulty RAM slot on Motherboard