Press your PC's power button once to fully discharge any remaining electricity in the components.
Open the official spec sheet or product manual to view the listed power supply metrics (e.g., 290W AC Power Supply or 500W 80-Plus Bronze PSU ).
Remove the side panel of your computer case (typically secured by two thumb screws at the back).
and flip the power switch on the back of the PSU to the "O" (Off) position.