Guitar Wiring and Pickup Modifications
This page and the following page contain a selection of modifications that can be done to your guitar's internal wiring and pickups to change or increase the range of tones available, and tips on techniques. Quite often it can be far more satisfactory to customise an instrument that you know well, than to replace it with a new one (That always sounds different when you plug it into your own amp anyway!).
Before You Start
Before you eagerly reduce your beloved guitar to a pile of bits, you will need to organise a suitable place to work and a few basic tools.
You will need an area large enough to lay your instrument on with sufficient space left over to accommodate your tools, and any dismantled parts laid out in a logical manner. It is a good idea to use a blanket or towel to rest your instrument on to prevent any damage to the back of the guitar. Similarly, a few strategically placed soft cloths or pieces of cardboard held in place with masking tape will protect the front from solder splashes and dropped tools.
The basic toolkit required to modify your instrument is:
- Small Phillips Screwdrivers (Sizes 0, 1, and 2)
- Small Slotted "Electrical" Screwdriver
- A Pair of Small Wire Cutters
- A Pair of Small Long Nosed Pliers
- Craft Knife
- Wire Stripper
- Box Spanners to fit nuts on Pots, switches and Jack Socket (8, 9, 10, 12 and 13mm)
- Soldering Iron (A 25 - 30 Watt Model is ideal)
Always keep your soldering iron bit clean and tinned. Do not use a file or sandpaper, the tip is coated and will not last very long once the coating is worn away, occasionally wiping the tip on a piece of damp sponge as you work will do the trick. To tin the bit, touch the end of a piece of cored solder to the tip until the metal flows over the bit, then wipe off the excess.
To make a soldered joint of, for example, a piece of hook-up wire to a component tag, first strip about 3mm of insulation from the end of the wire, then tin the exposed copper. To do this touch the soldering iron and the solder to the wire for a second or two until the solder melts and flows into the wire - do not use so much solder that you end up with a blob! Repeat this tinning process on the component tag (To practice, use an old jack socket) Now lay the tinned end of the wire on the component tag and apply the iron to the joint for a couple of seconds until the solder flows nicely over both parts. You will have to practice this to get it just right, aim for a nice shiny finish to the joint with the edge of the solder looking as though it is "wetting" the metal underneath. Try not to move the joint for a second or two as this will result in a "dry" joint that has a matt grey appearance and will not give a reliable connection.
Almost any modification to an guitar's internal wiring will entail the addition of at least one switch to switch between the new configuration and the original one. You can either use an additional DPDT (double pole, double throw) miniature toggle switch, which will require a small mounting hole (usually 6mm), or (if you are reluctant to attach your instrument with a cordless drill!) you can replace one or more of the tone or volume pots with a push-pull pot - this is a standard pot with a switch "piggy-backed" that can be actuated by pulling out or pushing in the shaft of the pot.
Different types of DPDT Switches
The illustration shows both types of switches, together with a schematic showing the arrangement of the contacts.
Coil Splitting a Humbucker
A short length of 4-core screened cable (approx 30cm)
Thin heatshrink sleeving, PVC insulating tape or (even better!) cloth coil covering tape.
PLEASE NOTE - this entails quite a bit of dismantling of your pickups. The wire used in guitar pickup coils is very small and highly delicate - any mistakes here could easily permanently damage your pickups - if you have any doubts about your ability to do this successfully (or have an expensive or vintage instrument), please do not attempt it! A competent repairer will be able do this for you for a reasonable fee.
Most replacement pickups are supplied fitted with 4 conductor and shield wiring - this allows complete freedom in how to connect the pickup, as it essentially gives you access to the start and end connections of both coils, and a separate ground connection to the backplate (and cover, if fitted). If you have older style pickups that just have a single core plus screen connection, it is possible to remove this and connect up a four conductor cable instead.
The following steps assume that the pickup has already been removed from the guitar.
Please remember that the correct orientation of the magnet(s) and coils is essential - as you remove parts, it is a very good idea to mark them with a felt tip marker, and make a rough sketch to ensure that everything is replaced in the correct position when you reassemble the pickup.
1 - Remove the metal cover (if fitted).
These covers are usually retained by both the adjustment screws and by a fillet of solder around the edge of the pickup. First remove the six adjusting screws, then turn the pickup over and inspect the rear edge of the cover - you will probably see that solder has been run around the edge of this, some times all the way round, sometimes just at two points. Unless you are skilled at soldering, and have a soldering iron with a high thermal capacity, I would not recommend trying to unsolder this. The method I have had the most success with is to first remove any "lumps" of solder with a small file, then to GENTLY and repeatedly score around the inside edge of the cover with a small craft knife - do NOT press hard, if the blade suddenly goes through, it could damage the delicate pickup coils beneath!
Once you have made a fairly deep score through the solder joint, gently "work" a small screwdriver blade between the cover and the pickup backplate, and, by gently twisting this and working it round, carefully break the solder joint. When you have broken the solder joint all the way around, you should be able to carefully remove the cover from the pickup. If the cover is obstinate, and you are sure that you have completely broken the solder joint, it is possible that the pickup has been wax potted, if this is the case, using a hair drier or fan heater to warm it up will usually soften the wax enough to ease disassembly.
2 - Remove the outer layer of tape.
At this stage, you should see that there is a layer of tape (usually a black cloth-based type) wrapped around both coils. Very carefully peel this back - a little heat from a hair drier or fan heater will help to soften the adhesive. The coils normally have there own individual tape covering, however, some pickups may not - if this is the case, be careful not to pull the fine wire up with the tape, as it is incredibly fragile! I usually find that gently pulling the tape backwards, rather than upwards is less likely to disturb the windings.
3 - Unsolder the coil connections.
Once the outer layer of tape is removed, you should see the insulated wires coming from the coils - one will connect to the "hot" conductor of the screened cable, another should be soldered to the braid of the cable and the metal backplate of the pickup, the other two will be soldered together and insulated with either a small piece of tape or a piece of sleeving.
You should make a sketch of these connections, noting the colours of the individual wires, then carefully unsolder each connection and remove the original output cable.
4 - Fit the 4 conductor cable and reassemble.
You should now prepare the end of the 4 conductor cable by removing about 50mm (2 inches) of the outer insulation, then, if the screen is braided copper, twist this together and tin it with solder (being careful not to melt the insulation of the inner cables!). If the cable has a foil screen and drain wire, remove the excess foil, leaving the bare drain wire free. Strip about 5mm of insulation from each of the 4 inner wires and again tin the ends with solder.
Next you will need to thread the cable through the hole or slot in the backplate that the original cable went through and solder the braid or drain wire to the metal backplate - this will usually require a reasonably hot soldering iron, as the metal backplate will conduct heat away from the joint. Let the backplate cool down before carrying on.
Now connect each of the four wires from the pickup coils to the 4 wires of the cable, insulating each joint with a small piece of heatshrink sleeving or tape, and tuck the wires between the bottom of the coils and the backplate, so that they are hidden and will not prevent the metal cover being refitted. Make sure that you make a note of which pickup wire is connected to each cable wire - if you are doing this mod to both pickups, ensure that you use the same colour scheme on each one.
Before you go any further, it is a very good idea to check your work using the resistance range of a testmeter (a small digital multimeter can be purchased very cheaply, and is an essential tool for the DIY guitarist). There should be a completely open circuit between any of the 4 conductors and the braid or drain wire, each coil should give a reading of somewhere between 1k (1000 ohms) and 10k (10 000 ohms), and there should be a completely open circuit between the two coils. If you find a very low resistance (less than say 10 ohms), this is probably a result of having melted the insulation on one or more of the 4 cable wires, or not having insulated the joints properly. If either of the coils has a very high resistance (greater than 20k), then either a solder joint has not been properly made, in which case you should resolder it, or you may have damaged the windings on one of the coils during disassembly, in which case you will have to get the pickup rewound by a repair shop.
Assuming that the above tests indicate that all is well, carefully reassemble the pickup in the reverse order of disassembly. If the pickup had metal covers that were retained by a fillet of solder, carefully burnish the previously soldered edges with a piece of fine emery cloth or a small file to remove oxides and old flux residues before refitting them. I would not recommend attempting to solder all round the cover (unless you are confident of your soldering skills), it is sufficient to solder them at four points - again, let the pickup cool down after this operation!
Congratulations! You now have a pickup with four conductor wiring which can give a total of six different wiring possibilities for your guitar:
a - Single coil (Coil 1)
b - Single coil (Coil 2)
c - Two coils in series
d - Two coils in parallel
e - Two coils in series (out of phase)
f - Two coils in parallel (out of phase)
Note that the pickup will only be humbucking in configurations c and d.