The dead Linksys power supply
Well, not quite a 'ring' but one red LED.
A few months ago my internet decided to cut out while I was working on a project in the middle of the night, so I went through the usual diagnostics of trying to reset everything, but with no luck. Closer inspection of the router revealed that only the red diagnostic light was on, and it was dimmer than usual. I assumed my router was toast but, decided to make a few attempts to get my internet restored that night.
I can't recall how, but I eventually reached the conclusion that the power supply had crapped out, so I went looking for another 5V power supply. Fortunately I discovered another old router that had one. A bit of soldering later, I had the connectors on the power supplies swapped and voila! It worked! So my internet was back up and I could finish the work on the project.
Now that was a few months ago, so why do I bring it up now? Well, Dave mentioned he had a dead WRT54G and explained the red light just blinked. It sounded like it could be a similar problem, so we plugged it in and the red light came on rather dim -- just like mine. Chances looked good that it might be the same problem. Checking the power supply with a multimeter we found it was 5V as it should of been. Not yet convinced the power supply worked, we popped open the router and checked the voltage when under load and sure enough it was 4V... Too low to power the router. To confirm the router itself works, we temporarily hooked up the 5V from a molex connector of a computer power supply to the router and it started up normally. Problem solved! Now we just need to locate a new 5V power supply for it...
So if you have a dead WRT54G in your closet with only a faint red light showing when you turn it on, you should try another power supply and see if you can give the beast a second chance at life.
Now, while we're on the topic of routers... I feel like I should mention Tomato -- the firmware Dave and I both use. It's got the nicest interface I've ever seen on an embedded device (complete with pretty graphs and smart use of Ajax). It also boots much faster than DD-WRT (although I've heard rumors that things like VPN don't work very well).
The red light of doom