Things You'll Need
Instructions
Turn off your PSP and remove any headsets or USB cables from the ports in its side. Then turn it over and slide the back battery cover off. Lift the battery out of its compartment.
Use your Phillips screwdriver to remove the four screws on each corner of the battery compartment, the two screws on the top and bottom of the side of the unit, and the single screw in the middle of the bottom of the unit.
Use your fingers to carefully pry the faceplate off the front of the device.
Use the tip of your screwdriver to gently pry up the rectangular button bar from its side at the bottom of the screen. This is the bar that contains the volume control.
Use your fingers to check the connection on the side of the bar where the ribbon cable plugs into it. Make sure the ribbon cable is connected tightly. If this doesn't fix your volume button, or the button itself is cracked or broken, unplug the ribbon cable and replace it with a new one (available from your PSP retailer or online), then reassemble your PSP in the reverse order you took it apart.