Remove the jack plate from the guitar body by unscrewing the nut around the threaded jack opening using the adjustable wrench. On some Hamer guitars, the jack plate is connected to the body by two screws. If this is the case on your Hamer, remove the screws using your Phillips screwdriver after you remove the nut.
Pull the input jack slowly out of the body to avoid ripping the wires connecting the jack to the pickups. The jack should have enough wire length to pull it out a few inches from the body.
Examine the jack input and look for broken wires. Push a 1/4-inch guitar plug through the jack input hole as you normally would if the jack were installed in the guitar. Verify that the metal tip of the guitar plug makes complete contact with the metal conductor of the jack input. If it does not, bend the metal conductor until it makes firm contact with the plug.
Solder a loose wire connection if the wire's original soldering is broken. The twisting motion of jack cords occasionally places too much stress on the jack components. Heat the solder point connecting the pickup wire to the jack input assembly until it is warm enough to melt the soldering wire. Melt soldering wire on the connection and hold the wire in place until the soldering wire cools and hardens.
Test the input jack before inserting it back into the guitar. Plug a guitar cord from an amplifier into your guitar and verify that you fixed the problem. Gently wiggle the jack cord and make sure that no popping noises occur through the amplifier.