by Mooselake » 2018-May-Thu-09-May
I've been using a similar 29A switcher for many years. Cut the proper connectors and wiring off an ATX supply and wire them to the plus (usually the yellow wire(s)) and minus (usually the black wire(s)) terminals on the new supply. For safety make sure the terminal strip is covered (I printed a plastic cover, then added in a PC style power inlet and a switch) to mine. Exposed mains voltages can be lethal, but it's easy to cover them or put the whole thing in an enclosure and protect yourself. I'm sure I've posted pictures, but can't find one via search; too wordy I guess.
One nice thing about these supplies is they have a voltage adjust. Fire up the bed and extruder heaters, and then adjust it for 12.0V. You'll find the hot bits will heat up a lot faster. It'll go over 12V when the heavy loads turn off, but per the board's designer it's good up to 19V (I couldn't find that post, but a reference to the max voltage from the DFM engineer).
Kirk
Modified KickStarter Classic Plus 7/2012
KS Thingybot Delta Pro 10/31/16
Creality Ender 3 Pro 12/2019