When repairing a low voltage wire such as a wall mount power supply a small solder joint covered in heat shrink can offer a low cost and professional looking repair.
Here we have installed an old barrel connector on a new wall mount power supply that came with only wire leads. By offsetting the splices we ensure you will not have a short in the wire. By covering this splice with heat shrink you have a smooth and clean splice with a minimal bulge. This same process can be used to repair a damaged cord by simply cutting a small portion out of the cable.