This will guide you through the replacement of your Power Supply.
Remove the parallel port cover on the back of the PlayStation.
Flip over the PlayStation and remove the six screws from the bottom.
Turn the PlayStation upright. Remove the cover by lifting it up.
Remove the two screws securing the power supply to the console.
Detach the connector from the power supply.
Lift up the left side of the power supply. Slide it to the left to remove it.