Dont what I would have tried but with a multimeter would have checked if the power supply was giving out the 12V (HH3 is so guess similar), says on the power supply and measure and see if it goes, You bought a new one so if that and not the router pulling to much power, just a bad psu when should sort it. Best thing to try. still just buying a new one from an expensive shop as maplin is for that sort of stuff, might have been a mistake, hopefully not as if that then onto a winner.
power supplies. ebay always a goodun. £5 would have got one. Maybe what you got was but when looking for stuff like that always seems a rip off.
disco light and gadgets, good, we have a maplin shop in oxford, disco stuff stuff christmas, nice stuff. PSU, I would not!.
Maybe an internal fuse inside. matter of taking it apart. Can you get hold of a multimeter. Can check the PSU and some internal fusing if there is some. A least go across the part of the board with the power rails on but if not into that stuff then maybe not a good idea.
I would go for the psu being a good bet some money well spent I would think.
Say what it was when going.
multimeter, done electronics mending and used to test electrics, has it's use.