No power to the radio

[Stax]

Hello all, it's a bit more complicated than that...

I've replaced the radio in my 2007 Aygo and it was working ok apart from the red/yellow wire swap for permanent connection to the Battery. Whilst doing that I very clumsily briefly shorted the red (direct connection to the battery) and black (ground) wires.

I've checked the appropriate fuse (all of them in fact) and they are all fine but I only get 4v from the red and black wires now, 12v when the car has started.

I'm stumped as to what might have happened and I'd be really grateful for any ideas. Thank you.

[Stax]

Well... I noticed that the internal light had no power as well so I assumed it would be an upstream fuse. I found the fuse box in the engine bay and there it was! A blown fuse. 

I have power but swapping wires to the radio didn't make any difference so surprise surprise my Russian ten pound special radio may be the culprit 🙄