The jack socket on guitar effects pedals can take quite a beating with regular use, and it is likely that at some point a connection inside the jack socket will fail, causing loss of signal to the unit. Thankfully, soldering the connections on a guitar jack input on an effects pedal is a straightforward task that every guitar player should be able to do.
Remove the back cover from the foot pedal to expose the internal electronics and permit access to the terminals to the jack socket. Depending on the model of pedal and its particular construction, it may be advisable to remove the socket from its location to allow easier access to the terminals -- unscrew the hexagonal retaining nut on the outside of the casing to facilitate removal of the socket.
Connect the soldering iron to the power; leave it in its stand. Make sure it is sitting on a solid surface as it warms up and you prepare the faulty connection for soldering.
Identify the faulty connection and prepare the terminal and wire for soldering. Remove any remaining wire still attached to the terminal by holding it with the pliers in one hand and applying heat from the soldering iron with the other. The residual solder will melt, allowing you to gently pull the old wire away, leaving the terminal free to be properly reconnected. When cool, clean the terminal thoroughly with a small piece of fine-grain sandpaper.
Trim the end of the wire to be connected to get a fresh end to work with. Strip no more than 1/8 inch of insulation from the wire to reveal the core, and rub the exposed wire with the sandpaper.
Prepare the two connections for joining by coating -- called "tinning" -- both the wire and the terminal with solder. To do this, apply a small amount of solder to the tip of the soldering iron, then apply heat to the stripped wire end and coat it in solder too. Repeat for the socket terminal.
Press the wire onto the terminal with the hot tip of the soldering iron. This allows you to release the wire and pick up your solder. When hot enough, the solder will easily flow to fill the gap when held against the joint, making a good connection. When the joint is fully coated, withdraw the solder and the iron, being careful to not move the joint. Avoid pulling on the joint for a few minutes as it cools and hardens.
Remember to disconnect your soldering iron and clean it with a damp sponge. Attach the socket once more if you had to remove it for access; then replace the cover of the pedal's casing.
Always solder in a well-ventilated space to avoid breathing the fumes from the solder.