Posted 02 October 2010 - 05:00 PM
Your fans are working because they are being powered by the power supply, which you said you replaced.
There is a circuit which is on the motherboard that the power button on the computer case activates to send a signal to the power supply, that activates the cooling fans, this circuit allows 12 Volts from the power supply to power up the cooling fans.
There are voltage sensitive components located through out the motherboard, that have an association with earth ground and chassis ground. It is through this circuit that electronic parts can be damaged from a high voltage such as lightening.
Parts such as diodes, integrated circuit chips (IC chips), electrolytic capacitors, voltage regulators and transistors can be damaged if voltage higher than their rating passes through them, thus burning open the circuits built into them.
If your Ethernet NIC is built into the motherboard and has sustained damage, your whole motherboard would have to be replaced. If even in the event, you were able to replace the chip, the chances are very good there are other components on the motherboard which have also sustained damage as well.
To diagnose your motherboard for failure, you would need the proper test equipment along with flow charts and circuit voltage charts to do a successful analysis, then have the ability of replacing surface mount components, which require the use of soldering tools used for micro circuitry repair. The use of a microscope or electron microscope is needed in some cases.
This is why todays electronics are known as disposable devices. The cost of repair far exceeds the price of a new one.
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