Soldering Tips & Tricks

Written by Kenny Prochazka

Many of us have looked at guitar or amp wiring and thought, "If I trusted my own soldering skills, I could do that myself." There can be a great deal of truth to that, and we are here today to explain what solder is, how it works, what different types are for and some practices to follow. Hopefully this will build your confidence to the point of saying, "I can do that."

The simplest way to describe solder is as a semi-conductive glue that holds your component connections together. Solder is metallic, but it is not conductive enough to carry much signal. Instead, you want to first make sure that you have good physical (or "mechanical") connections between wires, components, eyelets, lugs and/or turrets before fixing them into place with solder.

What types of solder are there?

For most analog electronic purposes, technicians will choose 60/40 (Tin/Lead) or 63/37 (eutectic) solder for ease of use (lower melting point and flows better, but is toxic). In plumbing, where drinkable water is a concern, lead-free solders such as SAC305 (Tin/Silver/Copper) or 95/5 (Tin-Antimony) are required. Hard solder (or Jewelry solder) is used to create multiple joints between precious metals.

In the world of guitar and amp electronics, we exclusively use a rosin-core solder, where the core prevents connection oxidation and corrosion. There are also acid-core solders that actively cause electrical corrosion, and solid-core solders that require a separate step of applying flux to clean the connections, but we tend to avoid those types.

What do I need to solder?

You will first want to make sure that you have a complete and well-stocked workstation. This could be a kitchen table or a hotel desk (IYKYK), but you want room to operate with all tools, supplies and components readily at hand.

In one of our previous articles, "Amp Building - Tips & Tricks", we gave a list of recommended supplies for any soldering job:

• A quality soldering iron with temperature control - This can ensure that you are supplying enough heat to run the solder, without also melting or cooking the component that you are attaching. Trust us, a cheap soldering iron will be more trouble than it was worth.

• A clear and stable work surface and area - Scrambling to find a tool, a part or a diagram is no fun, and can lead to serious problems if clutter gets in the way of your work. Also, make sure that your chosen workspace is separate or private enough that you can leave your build there while you aren't working on it - the more you move it around, the less you will remember where you were in the process.

• Plenty of high-quality 60/40 or 63/37 rosin-core solder - The right type of leaded solder is important for a good amp build, or guitar project, because it has a lower melting point and makes for more reliable joints. The rosin core will act like a flux to help the solder adhere.

• A well-ventilated area - The right solder is over 50% lead, and lead fumes can be highly toxic. Crack a window or set up a fan so that you are not sitting in your own cloud of fumes.

• One or more good sources of light - You want to be able to see as well as possible to avoid shocking yourself or damaging your work. Some builders use lighted magnifying visors to reduce eye strain if they are putting in long days.

For amp builds, you will also want to look into these:

• A decent multimeter with settings for voltage and ohms - Use this to check the values of every component, and also to check voltages when you are preparing to start up the amp for the first time. You do not need a fancy, expensive meter, just one that will consistently do the job correctly.

• A variac device for the final testing stages - This allows you to observe the behavior of your amp by slowly increasing the voltage, which can help you to find issues and save components before they go up in smoke or flames.

• A chopstick or other non-conductive probing tool - There are times when you will need to literally "poke" around inside of the amp to locate a loose/cold solder joint or test a component's functionality.

• A Mojotone Amplifier Chassis Stand - This not only gets the chassis up off of your work surface, but also allows it to be locked into different positions, depending on which part/side you are currently working on. Our chassis stand can fit almost any size and type of amplifier chassis.

For guitar or bass work, voltages will typically not be as crucial, but many technicians won't be caught dead without our Guitar Work Mat and Neck Rest.

How do I solder?

Now that we have our supplies, it's time to heat up the soldering iron and get to business.

1. You will want to make sure that your wires and components are clean and free of residue. New components should be good to go immediately, but it is always good to check.

2. Whether it’s putting components on an eyelet board, wiring up tube sockets or connecting wires to potentiometers, the main thing you want is a good solid mechanical connection between components. Solder is not a great conductor, especially some of the newer lead-free solder. (For example, when soldering to a tube socket, you want to create a hook with the wire or component lead, hook it through the pin, then use a pair of needle-nosed pliers to pinch the hook together around the pin. Now the wire has a solid connection to the pin, so even if solder were to fail, in theory you have the components connected together. After you have created the mechanical “bond”, then you can add a little solder to help solidify the joint.)

3. Especially with a new iron, tin the tip of your soldering iron and your wires by applying a small amount of solder. This helps to make quick, secure connections. Many of our wires come pre-tinned from the manufacturer, so you may not need to do much tinning of your own. A quick way to tell if your iron is hot enough (and clean enough) is to take a little solder and touch it to the tip. The solder should melt instantly and stay on the tip, NOT bead up and fall off.

4. When soldering a connection on an eyelet, tube socket or potentiometer, make sure that you are heating the component lead as well as the pin, lug or eyelet. (Do NOT melt the solder directly.) Then slowly flow the solder into the connection. The solder should liquefy and spread over the connection. It should only take about 2-3 seconds for the connecting component leads to become hot enough to flow solder. PRO TIP: It does not take a lot of solder to make a good connection.

5. Step back and inspect your work, looking for any missed connections or unfortunate cold solder joints. Gently tug on the wires and/or parts to make sure that they are solidly in place. PRO TIP: If you use too much solder, it will run and drip, which can cause unwanted shorts or grounds in your circuit. Clean up any excess solder before moving on. If you drip solder into the body of a potentiometer, it will most likely render the part unusable and in need of replacement.

6. Wash your hands if you have handled lead solder without gloves.

What is a "cold solder joint"?

A cold solder joint will appear dull, lumpy or grainy, rather than smooth and shiny. This indicates a faulty connection caused by insufficient soldering heat, resulting in poor solder bonding. This faulty bond often leads to signal problems, higher resistance or complete failure, so you want to fix any of these that you come across.

“You can do this!”

Now you have all of the basic information that you need to develop your soldering skills, so the only thing left is to grab your iron and get to work. With enough practice and the right components, in no time you will be able to find your sound and love your tone!