Raspberry Pi Ethernet jack stopped working yesterday and now

[leonardicus]

I've been running this particular Pi (model B) for a little over a year now with no issues. It runs a small server that I "set and forget," so my problems have not come about due to recent configuration changes. Long story short, my ethernet jack stopped working, and I now believe it to be faulty hardware.

Here are the trouble-shooting steps I have taken:
1) Using a known working router, with a known working ethernet cable, in a known working LAN jack on the router, I can connect my laptop and get internet access. Using this same configuration with my RPi (set for auto dhcp), I do not get any flashing on my LINK, FDX or 100 lights. Nothing after 5 minutes. Nothing after a reboot. Nothing in the RPi ARP cache. Therefore, I cannot establish a physical link with known working hardware.

2) Using the same known working ethernet cable, I tried manually setting an IP and subnet mask so that I could connect my computer directly to the RPi via ethernet. This did not work, and no lights on the board suggested the physical connection worked. Nothing in the RPi or laptop ARP cache suggesting the two know about each other. I cannot induce the RPi to form a physical connection in a working configuration.

3) Taking the "old" SD card from the defective RPi and plugging it into my second RPi, I can get a DHCP assigned IP address after 30 seconds and the link lights are all active on that second RPi. Therefore, my existing server RPi configuration is fine as tested using known good hardware, and there is nothing to suggest that there was some "bit rot" on the SD card.

4) Using a new SD card with the most recent stock Raspbian image, I can connect my second RPi via ethernet to confirm that DHCP assignments work by default. Using the stock Rasbian card with the defective RPi, I get no connectivity. Therefore, something is physically defective with the Ethernet jack or its connections.

I mentioned this was a "set and forget" server, and it sits in a protective case. There is nothing that I can see that is defective with the Ethernet jack (e.g., all 8 pins are straight and normal), and by slight wiggling, nothing looks or feels loose.

Is there anything else I can do? Since I purchased this board from Adafruit directly, is it possible to do an exchange?

[egutting]

Does the USB still work? I had the same problem with a Pi I had. The ethernet jack is connected to the USB and they can go out on the B. (I think I read it has something to do with the crystal running them X1 on the bottom of the board) I tried the fix that I found, but it didn't work and it now this particular pi runs my cupcade since it doesn't require the ethernet or usb jacks.

[leonardicus]

Both usb ports work. Good idea though.

[adafruit_support_mike]

You've done a good series of controlled comparison tests, so it does sound like the Ethernet module is dead.

You might be able to get more confirmation by scanning the output from `dmesg` and looking for the point where it tries to initialize eth0, but I doubt that would lead to a solution.

Our return period is 30 days, and mostly applies to manufacturing defects and early part failure. After that, it gets increasingly difficult to isolate production problems from environmental issues. The most likely cause of failure would be a voltage spike on the Ethernet lines, which could be caused by any number of things.. nearby lightning, spikes in the service power because a lot of air conditioners shut off at the same time, etc.