It's the wallwart power adapter. I've had 3 of these fail, they are not switching power supplies like the more modern ones. Basically just a big fat coil, 4 diodes and a capacitor (bridge regulator converts ac to dc) they run hot and fail especially when you plug/unplug/plug because that type of adapter uses a big coil for the ac side, when you unplug it's load, it causes a magnetic field to collapse causing a small surge in the adapter which just wears out the diodes and the coil eventually just fails. The router itself is fine, you can safely run another 12v 1amp adapter, I ran one on a 12v 3amp just fine. Router has built in voltage regulator, it won't consume then it needs.