Jumper Wires for DC Jack
We'll use the jumper wires from the DC plug we wired up earlier. These are just the just a little too long so we can shorten them – about 8cm long. These wires have a female jumper connector so they'll connect perfectly onto the potentiometer (for on/off capabilities) and DC plug. Using wire strippers, remove a bit of insulation from the tips and tin them with a bit of solder.
There's three terminals on the back of the DC jack. We'll need to attach the jumper wires to just two, the voltage and ground. Depending on the colored wires, you'll want to use the appropriate one of your choosing. The terminal with the large right-angled metal plating is voltage, the other two are ground. I recommend tinning the terminals before attaching wires.
I was able to prop up the DC jack with helping hands by clipping onto the barrel jack. It was not perfectly secure, but holds enough to keep it in place while soldering. Pieces of heat shrink tubing would have been nice here, optional of course. These terminals are too wide to fit into female jumpers so soldering is the best option.