RepRap for Science—How to Use, Design, and Troubleshoot the Self-Replicating 3-D Printer - Open-Source Lab: How to Build Your Own Hardware and Reduce Research Costs - page 152

FIGURE 5.55 Grouping and soldering the power supply wires.
Short the green wire with black ground in order to provide the 12 V from your black and
yellow as seen in Figure 5.56 . Do this by simply cuting the green wire and any black wire
from the 24 pin power connecter on the power supply and soldering them together. You can
then put some heat shrink tubing around the solder. If your power supply has a mechanical
switch on the back, a straight solder is fine; if there is no mechanical switch (i.e. you plug it in
to turn it on), you may want to wire a switch between the green and black wire to turn it on
and off easily.