So I’ve been playing around with openwrt on a router that I bought off of eBay and it wasn’t going well until I found this blog post:
The Weblog of Titus Barik » Blog Archive » Linksys WRT54G Brick:
If you have a constant on power and diagnostic LED then it’s worth checking your power supply before you bin it. My power supply had dipped to 4.6v under load, and was not enough for the router to run. With a stronger supply on the running voltage was 4.86v @ 1.1A Hope this helps others!