DO NOT WORK ON ANY ELECTRICAL
WHEN IT IS PLUGGED INTO

MAIN POWER! IT'S NOT WORTH

BEING DEAD! DON'T DIE,

UNPLUG THE SUPPLY!

With that out of the way this is a quick guide on how to modify a PC power supply to use with your printer.

I use this EVGA supply, it's got 360 watts / 30 amps at 12VDC and 17 amps at 5VDC. This is plenty for most printers. It runs my Anet A8 and my Creality CR10 S5.

Why?

These supplies are safe. They have over and under voltage protection, Surge, short circuit, overheat and overload protections as well as a fuse on the mains connections.

These supplies run cool and quiet with a nice big fan.
They can provide 12v and 5v, perfect for Octoprint
They really aren't too expensive. I get mine for about $35 delivered from amazon.com in the USA. Really any PC supply is better than the generic included ones with most machines.

Cons

You gotta rewire it.
No 24v options.

Step 1: Safety and Tools

SAFETY!

Unplug the supply from the wall and wait 30 min before working on it for capacitors to fully discharge.
Never open any electrical appliance when it is plugged it!
We are removing all the existing low voltage wires in the supply because on this size unit it's normally about 18AWG wire. This cannot handle the 30 amps of 12v on it's own. Not only that it's ugly to splice them outside the enclosure of the power supply.

Follow basic safety rules working on any electrical appliance.

Tools

Soldering Iron
Solder
Wire cutters
Wire strippers
A lighter or something for heat shrink

Supplies

XT-60 connectors
XT-30 connectors
12AWG silicone wire for 12v, I like the silicone for ease of use and heat resistance.
18AWG silicone wire for 5v
Heat Shrink Tubing

Step 2: Open to Power Supply and Remove Existing Wires

First open it up. Carefully remove the cover. Now I find it easier to
cut all the wires about 6 inches from the board to get them out of the way as well. You don't need them anymore. We are replacing them inside the power supply for a clean look plus the stock wires are not large enough to carry the current the printer will need. Then remove the PCB from the case so you can get to the bottom of it.
With the bottom exposed start to heat the rest of the wire connections and gently pull them out of the board. Do not remove the green wire that went to the 24 pin plug. This is generally labeled PSON or PSEN.
Clean up the solder pads so each group has 4 or so open holes clustered together.
Run the green PSON wire to one of the GND connection pads. This will keep the power supply on.

Step 3: Prepair the New Wires and the Board

Strip about half an inch off the end of the 12AWG wires. I bundle it into 3 groups to fit it through the board to the other side for solder. This is for the 12V+ and GND. Some power supplies have larger holes in the board which makes it easier to install these new larger wires. Be sure nothing is poking out the sides or crossing sections of the board.

Step 4: Lay the Wires and Solder

Be sure nothing it crossing into areas it should not!

Solder the wires securely. Don't be afraid to use plenty of solder here and trim up any extra wire left after soldering on the bottom. Check the top side too for any wires sticking out the edges or something.

Step 5: Solder the XT Connections on and Wrap Up

Solder the XT connections on the ends of the wires and heat shrink to prevent shorts. The connectors are marked for polarity and be sure to use the female ends on the PSU. You don't want live pins sticking out.

The larger XT-60 for 12v and the smaller XT-30 for 5v. This prevents crossed connections and has plenty of power handling.

I add some stick on rubber feet to prevent the supply from sliding off the table or scratching things.

Test the output with a meter and enjoy! That should be it You'll now have more available power and safer too!