Not wanting to spend the money on a dedicated power supply ... some traces and grounding a few pins on the protection circuit. The ATX supply [C] used could supply 25 amps on the 12 volt rail ...

a load resistor on the 5V circuit makes the power supply think it’s hooked up to a motherboard. It’s all wrapped up in a neat slant-sided 3D-printed case that fits onto the ATX power supply ...