Member Avatar for goose88

I have an XP SP2 PC that had a bad power supply. When I replaced the power supply, I found I could no longer pull an IP address It would get a private 169 address. I disabled the embeded NIC and tried a add on card. After that didn't work, I tried a usb wireless nic. It found the AP and said it connected, and ask for and accepted my WPA phrase, but I got for an address. To rule out windows I booted from a knoppix disc. I got the same result no connection. Oh, and for the record the router seems fine, I have wired and wireless devices on it with no issues. Any ideas? Thanks.

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As later confirmed, the real fault was a bad replacement power supply. A PSU can produce very targeted failures: undervoltage, excessive ripple, or intermittent rails can leave a NIC or USB radio powered enough to enumerate but not to complete a DHCP transaction. ’s suggestion to exercise the DHCP client is useful in software-level troubleshooting, but electrical instability will often defeat those steps.

Practical checklist to reproduce and isolate the issue:

  • Inspect logs/drivers: Windows Event Viewer and Device Manager or Linux dmesg/journalctl for NIC/USB errors.
  • Capture the DHCP exchange to see where it fails. Look for the sequence DISCOVER → OFFER → REQUEST → ACK; absence of DISCOVER means the client isn’t transmitting, offers without ACK mean the client isn’t completing the handshake.
  • Try the adapter on a known-good machine or use a powered USB hub for USB radios to rule out power delivery from the chassis.
  • Verify router-side: DHCP pool size, MAC filtering, client isolation, and router logs for offers to the client MAC.

Example commands to run while reproducing the failure:

Windows:
ipconfig /all
ipconfig /release
ipconfig /renew

Linux:
sudo dhclient -v wlan0
sudo tcpdump -n -i wlan0 port 67 or port 68

If PSU problems are suspected: test with a known-good supply before replacing other components, check for swollen capacitors or scorch marks, and avoid opening power supplies unless qualified. After swapping to a reliable PSU, rerun the captures and logs to confirm the DHCP handshake completes. Collecting a packet capture and a system log before swapping parts makes root-cause verification easy if the problem returns.

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Member Avatar for zeroth

I've re-read this a few times and the only things that occur to me are to first, once you get the acceptance of the password and get the address, /release and /renew the IP address (I'm guessing, however, that you've already tried that)?

That doesn't help your problem with the power supply though and that's what it has to be logically. You might review both the power supply itself (with whomever you got it from) and all the connections. Take dirt inside the case as part of your troubleshooting as well - a piece of dust could have become dislodged somewhere.

commented: It was the replacement psu. It was used. Thanks +5
Member Avatar for goose88

Thanks for the suggestion. I ended up replacing the replacement power supply, and it solved my issues. It's funny that it effected it that way.

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