A7V600X: LAN LED no longer on

  • Thread starter Thread starter Stan
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Stan

I have just built a box with the A7V600X. For 1 day the orange LAN LED on
the I/O panel would be lit and I could connect to my DSL modem. Now the LED
never is on (and the LAN status LED on the modem doesn't light-up, either,
of course). In the BIOS both "Onboard LAN" and " Onboard LAN Boot ROM" are
enabled. I haven't found a FAQ on the ASUS site that solves this problem.
 
Stan said:
I have just built a box with the A7V600X. For 1 day the orange LAN LED on
the I/O panel would be lit and I could connect to my DSL modem. Now the LED
never is on (and the LAN status LED on the modem doesn't light-up, either,
of course). In the BIOS both "Onboard LAN" and " Onboard LAN Boot ROM" are
enabled. I haven't found a FAQ on the ASUS site that solves this problem.
Click to expand...

What does XP's Device Manager indicate about the LAN? There probably is a
Troubleshooting button associated with it. Could try Refreshing or Unloading
and Reloading driver.
Billh
 
What does XP's Device Manager indicate about the LAN?
Click to expand...

"This device is working properly"

There probably
is a Troubleshooting button associated with it. Could try Refreshing
or Unloading and Reloading driver.
Click to expand...

I did this and it didn't help...
 
Stan said:
"This device is working properly"



I did this and it didn't help...
Click to expand...

The Ethernet RJ-45 connector interfaces to the RTL8201BL PHY chip.

1) Have you changed cables recently ? If you swapped a crossover for
a straight thru cable, maybe this would happen ? I think there are
some PHY chips that can reverse the wiring on their own (the feature
is called MDI/MDIX or something), but I don't see that mentioned
in the Realtek datasheet.

2) My experience with PHY chips, is they are autonomous at power up.
The chip should be able to auto-negotiate with the device at the
other end of the cable, even before the BIOS or other software
talks to it. Things that can hold the chip up are:

a) RESET signal remains asserted after board powers up. The
appnote for the 8201BL suggests reset can be done with an
RC timer circuit.
b) Some kind of powering problem with the PHY chip. It runs off of
+3.3V and makes its own 2.5V with an internal regulator.
c) The 25MHz crystal oscillator (see tin can next to 8201BL) is
not working properly. Sometimes a dry solder joint can do it.

For these faults, you'll have to visually inspect the circuitry
around the 8201BL chip, to see if anything is cracked, or
there are cold solder joints etc. If something is shorting to
the underside of the board, in the area of the network interface
circuitry, for example, that could also stop the circuit. The
oscillator is a high impedance circuit, and a spilled Coke on
the surface of the board could be enough to affect it.

If the 8201BL is set up to use the RC reset circuit, then something
you can try to get the LED back on, is turn off and unplug the
computer for a while. When you plug the computer back in and
turn it on, the reset circuit should have a chance to reset the
8201BL. Maybe the LED will recover after you cycle the power.
If this helps, it indicates there is something wrong with the
way that the reset is implemented.

Otherwise, pull the board and inspect it for damage.

It is even possible that the LED itself, on the rear connector,
has a dry solder joint. You can only see that by inspecting the
bottom of the motherboard.

HTH,
Paul
 
(e-mail address removed) (Paul) wrote in [email protected]:
1) Have you changed cables recently ?
Click to expand...

snip

No, this was the first cable I had used. But as the IT guy at my job said,
"It's the cable, stupid." And it was. Changing the cable solved this
problem.

Thanks for your help.

Stan
 
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