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Soldering is a method of using a conductive material (solder) to connect a wire with another device, such as another wire, a 1/4 inch plug, a guitar pickup or a circuit board. Solder is a metal alloy with a relatively low melting point; you can think of it as conductive glue. Electronics solder is usually composed of some combination of lead, tin, copper and/or silver.
Cable or pickup problems that can be solved by soldering occur when an internal connection has been physically severed, either at the solder point in the connector or further along in the wiring. For example, if the connections in your cable’s plugs appear undamaged but the cable has a visible kink or abrasion, then this is probably where the wires have been broken.
Unbalanced instrument cables, such as guitar cables, are among the simplest to repair, so if you’re new to soldering, they’re a great place to begin.
Understanding Your Cable
When you unscrew the metal cap over the 1/4 inch plug (the connector), you’ll find two wires, one bare and one insulated. In an undamaged cable, the bare wire (the ground) will be soldered to a metal tab that connects to a piece called the sleeve. This tab is crimped to the cable housing, serving as a strain relief. The insulated wire (the conductor) is attached to a smaller tab near the center of the connector, which joins with the connecter’s tip. The insulation prevents the two wires from touching, which can cause shorts. Each wire must be attached to its respective tab for the cable to function.
Cleaning and Prepping
Problems arise when one or both of these wires becomes disconnected from its tab. In some cases these wires require very little clean up and can be re-soldered to the tab without much fuss. However, if a wire has become frayed or broken in a way that it cannot form a solid connection, you’ll need to cut both wires and start fresh.
To begin, use cable cutters to cut the cable just past the strain relief. Use a sharp knife to remove about an inch of cable housing, taking care not to damage the shielding, which often contains the ground wire. Use wire strippers to strip just enough insulation from the conductor wire to form a solid connection with the tab. Uncrimp the strain relief with either a flat screwdriver or a sturdy pair of pliers. Try not to bend the crimp too much; you will need to use it later.
Before reattaching the wires to the tabs, you’ll need to remove any old strands of wire from the tabs. Do this by heating the old solder with a soldering iron until the solder begins to melt and then using a set of pliers to pull away the remaining wire. When using the soldering iron, it’s helpful to remember that the sides – not the tip – will be hottest. Use some kind of clip or jig to hold the connector in place while you work and avoid touching the connector with your bare hands; you’ll be surprised how fast heat from the iron can transfer to the plug. Keep the tip of the iron clean by wiping it periodically on a damp sponge. Avoid touching the soldering iron to the plastic insulation.
Making the Connection
To begin forming the new connection, use the iron to heat both the tab and the wire. Once these surfaces are sufficiently hot, you can usually melt a bit of solder by holding the solder wire next to the iron, where the tab and the wire meet. This will help you avoid a cold solder, a common soldering mistake that occurs when the wire and tab are not sufficiently heated and solder is simply melted on top of the wire.
Use only as much solder as needed to form a solid connection, and keep the surface as flat as possible. This can be a frustrating process at first, as solder hardens quickly once heat is removed and flows readily when heat is reapplied, sometimes making it difficult to get it to lie flat. You can use clips to hold the wire against the tab to help ensure a flat surface.
When you’re satisfied with your connection, let the solder cool for a few minutes and then give it a gentle tug to make sure it holds. Next, test the cable to see whether the problem has been resolved. If all goes well, use pliers to reattach the strain relief to the cable.
Don’t be discouraged if your first attempts are less than pretty; soldering is a hands-on skill that takes practice and patience to master. Other audio cables, such as XLR and TRS cables, are made more complicated by additional wires and configurations that vary by manufacturer. As the connections become more complex, it becomes increasingly important to understand the purpose of each connection, a topic beyond the scope of this basic introduction. To learn more about making and repairing audio cables, we recommend John Hechtman and Ken Benshish’s text, Audio Wiring Guide (Focal Press).