In this Part 1 video, I walk through how I “test” and validate a PC power supply the right way—starting with the simple stuff and building up to more capable tools. The big takeaway is that just because a PSU turns on doesn’t mean it’s healthy. I show you how I safely bring up an ATX power supply outside of a PC case, what rails I’m looking at (+12V, +5V, +3.3V, and +5VSB), and why having a repeatable process matters when you’re troubleshooting random reboots, no-boot situations, or weird stability issues. I also compare a few common approaches: a basic 24‑pin ATX jumper bridge tool to power the unit on, a generic LCD PSU tester for quick pass/fail checks, and then I introduce the Thermaltake Dr. Power III tester for more modern connector support. From there, I show how an ATX DC power supply breakout board makes it easier to probe and measure what’s actually happening on each rail. No sponsorship here—these are just the tools I’m using so you can learn fast, test with confidence, and avoid guessing when a power supply is the real culprit.