How To Solder
I often find that, when talking to someone who wants to change their pickups, they’re so worried about the soldering aspect that they’re either completely put off, or they decide they’ll need to to pay a tech (or perhaps me) to install them. While of course I’m happy to help, and maybe collect a little beer money, it’s really not necessary. Yes, soldering can be an amazingly complicated and difficult skill, when we’re talking about tiny printed circuit boards and incredibly sensitive components. But inside a guitar, we have quite thick wires, which connect to nice big terminals – usually in the form of looped lugs. We have plenty of space. And most of the components we use are very difficult to damage – in most cases, the worst possible result of a mistake is that we need to unsolder something, clean it up, and do it again.
In this article I’ll take you through the various things you’ll need to know about soldering to work on your guitar. You’ll need to know how to protect your guitar, how to solder to lugs, how to de-solder wires, how to clean contacts,and how to solder to the back of a pot. But first, lets make sure we’ve got the right equipment.
Firstly, you’ll need a soldering iron. It doesn’t need to be expensive, although if you’re doing a lot of soldering, you might like to get a temperature-controlled soldering iron. A 25W iron isn’t really powerful enough. I do all my soldering with a 40W iron, which is just right. A chisel tip or pencil tip are both fine – it’s more a matter of what works best for you. Start with a chisel tip if you’re not sure. A soldering stand is essential, as is a sponge for cleaning the tip.
Like a lot of things in guitar wiring, the type of solder you use attracts a reasonable amount of superstition regarding tone. Take it from me – you don’t need to worry. Just get something that is called “solder” and you will be fine. For guitar work, thin solder is better than a thicker type. We’re talking less than a millimetre in diameter, ideally.
Like a minor cast member in the movie Total Recall, soldering can make you wish you had three hands. You’ll probably do just fine with two, but if you do find you’re having trouble, I recommend getting a “helping hand” – basically a stand that has some moveable clips on it. You can use it to hold your work in the desired position, leaving your hands free for the task at hand.
Other equipment I like to have to hand: tweezers, needle-nosed pliers, a solder pump and some solder braid.
Protecting your guitar
When you’re working with solder, occasionally a small drop of hot solder will “escape”. If this lands on the finish of your guitar it will instantly make a hole. So, before you do any soldering, put rags or thick card all around the guitar and make sure they’re secure. If there’s a guitar you’re doing a lot of work on, or you’re going to be soldering in a lot of the same type of guitar, you could make a “soldering shield” for that guitar. This is a piece of thick card big enough to cover a decent area of the guitar, with a hole cut in it the same shape as the wiring cavity. It can come in very handy.
While we’re on the subject of protection, it’s also worth wearing safety goggles – at least until you’re confident you’re in control of your solder.
Soldering iron care
The tip of your soldering iron should always be clean and shiny before you use it to do any soldering. If it’s dull and dark, heat it up and wipe it on a wet sponge. If this still doesn’t help, you can melt some flux-core solder on to the tip and then wipe it, which will work, or you can clean it with flux, or a specialised soldering cleaner.
It’s important to note, though, that making the iron completely clean of all substances is what makes it go dull. The iron is oxidising, which is what makes it go dark. You need to keep a tiny bit of solder coating on the tip – this is known as “tinning” the tip.
When you turn your soldering iron off, it’s likely that it will go dull again as you let it cool. If you want to avoid this, you can continuously wipe it on your sponge until it is completely cool, which will stop the thin coat of rust from forming.
Transferring heat from your soldering iron
Once you have a clean and shiny tip, you are well-placed to start soldering. It’s important to note that the point of the soldering iron is to get your other components hot – not to melt solder itself. Depending on the shape of the tip you’re using, and the shape of the components you’re heating, you may have a little trouble. A useful tip is that you can apply a tiny drop of solder to the tip of the iron, which, when pressed against the component, will mold itself to the component’s shape and transfer heat much more quickly. However, you need to be aware that letting a blob of solder stay hot for a long time will oxidise the solder and ruin it. This follows on into everything you do – don’t apply heat for long periods of time. If after a few seconds you find you can’t get the job done, remove the heat and regroup.
Making a solder joint
OK, here we are at the part where we solder a wire to a contact. The most important thing to remember here is that solder isn’t glue. You shouldn’t use it to fill a gap between two pieces of metal, and you shouldn’t try to apply it to both surfaces and stick them together. You should think of it as being added security for an already-functional mechanical joint.
Before you bring the end of a wire to a component, you need to tin the end. Twist the strands together, apply the iron to the wire, and then when it’s hot enough, take a little solder to the wire as well. It will quickly soak into the strands of the wire. Apply as little solder as possible here – the aim is simply to hold the strands together and provide a surface that solder will readily flow to. For “pushback” cloth-covered wire and single-core bell wire, tinning is less important, but for multi-strand wire it’s crucial.
Most components in guitars have solder lugs – they’re little loops of metal that are incredibly handy, because they give you a “hook” you can use. Poke the wire through using your fingers, or tweezers if necessary, and bend it so that it holds steady. The wire should be firmly touching the contact, not hovering somewhere near it. Bring in the soldering iron and use it to heat both the wire and the lug. Once they are hot, you can feed a little solder into the joint – not on to the iron! You don’t need loads of solder – an ideal solder joint will be shiny and small, and you may even be able to still see the individual strands of wire through the solder. Once you have solder in there, remove the heat.
It’s important that nothing moves while the solder is liquid. If anything does move, you’ll see the joint go dull. This is a dry solder joint and it will cause you trouble, if not immediately, then soon. Re-do it now instead of having to strip the guitar down again in six months’ time!
If you’re switching pickups, rather than wiring a new guitar, then your first job with the iron is going to be removing the old wires. This is easier than soldering – all you really have to do is melt the solder that’s already there, and, while it’s still liquid, remove the wire. I like to do this by getting a grip on the wire I’m removing with some pliers first, and applying just a little tension. Like this, you can feel when the solder has melted and just pull the wire away.
Since you’re likely to be soldering to the contact from which you just removed a wire, it will help you to clean the contact if there’s a lot of solder left on it. For example, if you’re working on a volume pot, the three lugs have holes in them for you to loop the wire through – but these loops can easily get closed off with solder.
To clean up, you can either use solder braid or a pump. Solder braid is good for when you really need to get every last bit of solder off. You put the braid on the contact, apply heat to it with the iron, and then when the solder melts it soaks into the braid. More often, though, you’ll just need to get the bulk of the solder off, and this is more easily done with a solder pump. You “charge” the pump by pushing the plunger down until it clicks, melt the solder with the iron, and then put the nozzle of the pump against the melted solder and push the button on the pump. It creates a momentary vacuum that sucks the melted solder up into the pump.
Here’s a video demo showing how to de-solder a wire from a lug, and clean the lug ready for future use.
Soldering to a pot
The backs of pots are commonly used as grounding points for other components in the guitar. However, soldering to a pot can be difficult, as the large amount of thick metal is capable of absorbing a lot of heat without getting hot enough to melt solder. If you’re not careful, this can lead to heating the pot for such a long time that it overheats the pot’s internal resistive strip, and the pot stops working properly.
There are a few tricks to soldering to the back of a pot. Firstly, pots often have an oily coating when they’re new. This isn’t helping. Also, the smoothness of the pot can mean that solder has nothing to “grip” on to. You can solve both of these problems by giving the back of the pot a thorough going-over with some fine grit sandpaper or a wire brush.
Once you’ve done this and you have a nice roughed-up surface, you can also tin the back of the pot. Apply some solder to the iron, and then bring this to the pot. It will quickly heat up the part of the pot it’s touching and flow on to the pot. When this happens, spread the solder around with the iron and you now have a tinned surface that will be easier to solder to.
When it’s time to actually solder a wire to the pot, it’s more difficult than soldering to a lug because the back of the pot won’t help you by holding the wire in place. If you can rig up some clips to hold the wire firmly then that’s what you should do. Then you can just heat the wire and the pot, feed some solder into the join as before, and you’re done.
If you can’t rig up clips to hold the wire in place, then you can use my method. You have to have everything ready beforehand as it needs to be done swiftly. Your right hand will be used for the soldering iron and your left for everything else. So, to your left, place your solder, your needle-nosed pliers and the wire. Bring the wire to the back of the pot, and hold it in place with the soldering iron. With your other hand, bring the solder in and make the join. Now quickly put the solder down and pick up the needle-nosed pliers. Use the pliers to hold the wire in place and remove the iron. The solder dries, and now you have your nice clean solder joint to the back of a pot.
I try to avoid soldering to the back of a pot whenever possible. Often, I will tin all the ground wires together, wrap them in heatshrink, and take a single wire from there to a pot. This means only a single solder join to the pot is necessary instead of several, which makes things much easier. You can also find solder lugs that you can sandwich between the pot and the guitar, and solder to those.
Learning to solder is an essential skill if you want to be able to repair your guitar on the go. There are times when your guitar might just cut out – but it’s actually only one loose wire. Being able to quickly reattach it instead of taking it to a tech will save you time and money – and you might even enjoy it. I certainly do.