Guitar input jacks are subject to a lot of abuse. Plugging and unplugging of the guitar wire can cause the jack's holding nut to loosen over time, causing it to turn and twist the internal wiring--sometimes resulting in wire disconnection. Repairing the jack's wiring is one of the easiest guitar electronics repair jobs, requiring only simple hand tools and minimal soldering skills. Most guitar jacks are connected with two wires, a "hot" positive wire and a "ground" negative wire, and is the part of the guitar that sends the signal from the guitar's electrical components to the amplifier via guitar cord.
Remove the jack mounting plate from the guitar (the metal plate that holds the jack in place), by unscrewing the jack mounting plate screws with a screwdriver.
Pull the jack plate gently from the guitar to remove the jack and expose the connection wires.
Identify the positive and negative wires by viewing the wires. The positive wire will have black or red insulation, while the negative will be either bare wire, or have green insulation.
Identify the positive and negative jack solder posts by viewing the jack. The negative post is on the outside edge of the jack, and the positive post is on the inner edge of the jack. It is rare that both wires will be disconnected (making it obvious where to solder the loose wire) but if it does occur, it is necessary to connect the wires to the correct jack posts.
Strip about 3 mm (1/8 inch) of insulation from the wire (except when the wire is bare) by placing the wire stripper on the wire, applying moderate pressure and pulling the insulation away to expose the raw wire.
Plug the soldering iron into an electrical socket and allow to heat for five minutes.
"Tin" the wire by placing the soldering iron tip against the wire for several seconds, and apply a small amount of solder. A properly tinned wire will have a thin, even coat of solder covering the circumference of the wire surface.
Place the tinned wire onto the jack solder post and apply the soldering iron tip on top of the wire to hold it in place, while simultaneously applying more solder to the wire and post joint.
Remove the soldering iron and solder from the joint when enough solder has melted to cover the wire and post, and allow to cool for several seconds. It is important to hold the wire in place during the cooling process to keep it in contact with the jack post.
Repeat the soldering process for the second wire (if applicable).
Tighten the jack's holding nut with pliers (if loose) while holding the back of the jack with one hand.
Push the jack and plate back into the guitar, and replace the holding screws with a screwdriver.
Plug the guitar into an amplifier with a guitar cable and check for operation.
If your guitar does not have a jack mounting plate (when only the jack is visible) access the jack by removing the plastic or metal plate on the back of the guitar by removing the screws with a screwdriver. All repair operations are the same, except that the jack does not have to be removed from the guitar.
If your guitar is an acoustic-electric, or semi-hollow electric guitar with no jack plate or rear access panel, the repair should be entrusted to a qualified repair shop. Jack repairs on these guitars is generally quick and inexpensive but requires specialised tools and experience to avoid accidental disconnection of other component wires.
Use caution when working with hot soldering irons, and always unplug the iron immediately after use. Soldering irons can cause severe skin burns.
Wear eye protection when soldering, as molten solder can unexpectedly spatter and cause eye injury.
Avoid tightening the jack mounting screws too tightly to prevent stripping the screw holes. If the holes are stripped, inserting a toothpick dipped in wood glue and breaking it off flush with the surface will repair the hole.