• Testing pickups (impedance and functionality).
• Mapping out a switch.
• Testing a guitar cable.
• Identifying the lugs on a TRS output jack.
• Checking battery life.
Testing pickups. On many occasions I’ve used a multimeter before buying a used pickup. I learned the importance of this the hard way when I bought a used pickup at a guitar show, only to discover it didn’t work when I got it home. If I’d brought a multimeter with me, I could have tested the pickup on the spot and saved some money.
It’s a simple process to test a pickup. Set the multimeter to the ohm setting and touch its red test lead to the pickup’s primary lead (hot) and touch the black test lead to the pickup’s ground wire.
Photo 2
If you’re testing a humbucker with four conductors, make sure that the wires are properly attached to each other. For example, before you try to measure the impedance on a Seymour Duncan humbucker (Photo 2), make sure that the red and white leads are connected to each other and isolated from any other connection, and the green and bare leads are also connected to each other. Touch the red test lead from the multimeter to the black wire—the pickup’s primary lead. Touch the multimeter’s black test lead to the green and bare ground wires on the pickup. This should give you an accurate impedance measurement.
To make sense of a particular model pickup’s reading, check with the manufacturer for its exact impedance. If the impedance measurement you take is significantly lower than the manufacturer’s rating, then you know there’s something wrong with the pickup.
only to find you have no signal?
A multimeter can tell you a lot about a pickup before you wire it up. For example, humbuckers typically measure at around 8k ohms for a vintage-style pickup to as much as 25k for a high-output pickup. The 16.25k reading we see in Photo 2 indicates this is a hot humbucker. Single-coil pickups can range from 6k (vintage) up to 16k (high-output).
Mapping out a switch. If you don’t have a diagram to follow, wiring a new switch can be frustrating. An easy way to save time when tackling a wiring project is to use your multimeter to map out the switch. Simply set your multimeter to the continuity setting, which is marked with a speaker or soundwave icon. This setting will produce an audible tone to let you know when a circuit is closed.
Photo 3
On a 3-way toggle switch, for example, touch either one of the side lugs with one of the test leads from the multimeter, then touch the middle lug—that’s typically the output—with the other test lead (Photo 3). If you hear a tone, then you know the switch is on in that position. If there’s no tone in that position, the switch is off.
Photo 4
It’s a similar process for a Strat-style 5-way blade switch (Photo 4). Touch the last lug on the switch—this will be the output lug—with one of the test leads from the multimeter. Then touch each of the other lugs with the other test lead and listen for the tone. By carefully working through each switch position, you’ll be able to locate its corresponding input lug. As you map a switch’s connections, draw a diagram so you’ll have something to refer to in the future.
Testing a guitar cable. Have you ever arrived at a gig or rehearsal only to find you have no signal? The worst part is not knowing where the problem lies. Is the amp blown? Does the guitar have a loose output jack? Chances are it’s the guitar cable—that’s the place to start troubleshooting. The good news is, it’s quick and easy to test your cable with a multimeter.
Photo 5
Set your multimeter to test continuity, then touch the tip of both cable plugs with the test leads (Photo 5). If you hear a solid tone, you have a connection. But don’t stop there: Move the cable around a little to see if it has a short, and test it again. If after shaking the cable and testing it several more times you continue to get a solid tone, you can assume the cable is good. However, if the test tone is intermittent you’ll know there’s a problem. You should also test the ground on the cable. Simply touch the shaft of both plugs with the test leads and listen for a solid tone.
Testing a TRS jack. The output jacks on passive guitars are pretty simple—they have one lug for the primary lead and one for the ground. However, output jacks for an active system have three lugs. Called a tip/ring/sleeve (TRS) jack, these are common in electric guitars with active pickups or onboard circuitry, and are found in most acoustic guitars equipped with an internal preamp. The tip is for the primary lead, the sleeve is for a battery switch that turns the battery on when a cable is plugged into it, and there’s also a ground to complete the circuit for the electronics.
Sometimes the lugs for the tip and sleeve are different lengths, which makes them easier to identify, but many TRS jacks have the same length lugs with no markings to let you know which one is for the battery and which one is for the primary lead. This can be problematic if you’re installing a new pickup system into an acoustic guitar, adding active electronics to a solidbody, or troubleshooting an existing setup. But once again, the multimeter makes it easy to sort this out.
Photo 6
First plug a guitar cable into the output jack and switch your multimeter to the continuity setting. Touch one of the test leads to the tip of the guitar cable’s exposed plug and touch the other test lead to one of the lugs on the TRS output jack (Photo 6). Listen for a tone to identify which lug makes the connection. The lug that gives you a tone while you’re touching the plug tip is where you’ll attach the primary lead from a pickup or preamp.
Next, while still touching the plug’s tip with the test lead, touch the other lug on the jack. There should be no tone. Keep your test lead on that lug and move the other test lead from the plug’s tip to its shaft. You should hear a tone. This identifies the lug you’re currently touching as the battery switch for the active electronics in your guitar.
Testing batteries. Given the amount of battery-operated gear most guitarists have in their rig, it can be a challenge to stay on top of available battery power. You don’t want to arrive at a gig with a dying battery in a stomp, but you certainly don’t want to swap out all the batteries in your gear before every show. Some may still have plenty of life in them, so why not do a battery check to get the facts? (Of course, once you reach a certain number of pedals, it makes economic and ecological sense to get a powered pedalboard and be done with batteries.)
In the early days of rock ’n’ roll, guitarists would test a 9-volt battery by touching its terminals to their tongues—not a very accurate (or sanitary) approach. If you received a mild shock, the battery was deemed gig-worthy. The best way to test a battery is with a multimeter. With it, you can test just about any type of battery: AA, 9-volt, lithium, or even a disc battery.
Photo 7
Set the multimeter to the DC V setting (and if your multimeter offers it, to the appropriate voltage range). Now touch the red test lead to the plus battery terminal and the black test lead to the minus terminal. The multimeter will display the battery’s voltage (Photo 7). If you’re testing a 9-volt battery and the display on the multimeter reads less than 9 volts, the battery is weak. If the battery measures 9 volts or more, you’re good to go.
Each guitar has its own resonant frequency. Some guitars are bright, some are darker, and some are just flat-out midrange heavy. In large part this has to do with the density of the wood and the quality of the hardware, which helps explain why certain makes and models of pickups can sound fabulous in one guitar, but not so good in another. If your humbuckers sound too dark, rewiring them could be the perfect solution. It’s certainly worth trying before you replace them.
Some background. The two coils in a humbucker are typically wired in series. This produces the highest output, but also the darkest tone. If a humbucker has a 4-conductor harness, its coils can easily be wired in parallel. In this configuration, you lose about 20 percent of your volume, but the tone is brighter and cleaner.
When a humbucker’s coils are connected in series, the signal path of the first coil flows through the second coil and then on to the pickup selector switch, volume pot, and output jack. When wired in parallel, the two coils still operate together, but the signal path doesn’t travel from one coil into the other.
Photo 2
Planning the procedure. Stock Seymour Duncan JB and Jazz humbuckers are wired in series. Before we can modify the 4-conductor harness to wire the coils in parallel, we need to understand the Duncan color codes (Photo 2). Except for the bare ground wire, each colored wire is either the “start” or “finish” of a coil. How these wires are connected determines whether the pickup is wired in series or parallel. Here’s the breakdown:
• Black is the start of coil 1.
• White is the finish of coil 1.
• Green is the start of coil 2.
• Red is the finish of coil 2.
• Bare wire is always the ground.
Note: This applies only to Duncan pickups—other manufacturers use different color-coding schemes. See “Obey Your Color Codes” for more details.
Photo 3
Photo 3 shows these five wires connected in a series configuration. We have the black wire acting as the hot or primary lead, and the red and white wires are soldered together to create the series link (that is, they connect the two coils).
Fig 1
The green wire is connected to the bare wire and then soldered to the back of a pot to create a ground. Figure 1 shows how the hot wires connect to the 3-way blade switch for series wiring, and how the switch itself is configured.
Photo 4
Photo 4 illustrates how to connect the wires of a 4-conductor Duncan humbucker in a parallel configuration. As you can see, black and red are joined—they become the hot or primary lead. White and green are connected to the bare wire to become the ground, and all three are soldered to the back of a pot. The parallel wiring diagram for the 3-way switch is show in Figure 2.
Fig 2
By wiring the humbucker in parallel, we have connected the start of coil 1 to the finish of coil 2. For the ground, we have connected the finish of coil 1 to the start of coil 2 and both are joined to the bare wire.
Doing the deed. After removing the strings and pickguard, unsolder the pickup wires from the switch and pots, being careful not to overheat them. Separate the wires from each other with your soldering iron. Next, twist and solder the black and red wires together. Do the same for the green and white wires, and join them to the bare wire. Now solder the black and red to the input lug on the 3-way switch, and the green, white, and bare wires to the back of one of the pots.
That should do it. Put the pickguard back on, restring, and test out your new tones.
Obey Your Color Codes
Different pickup manufacturers use different color codes for their 4-conductor humbuckers, so before you start brandishing that hot soldering iron, make sure you’ve got the right color codes and have figured out how to connect the wires. Here are a few parallel wiring combinations for several other popular pickup manufacturers.- DiMarzio: Red and white are hot, black and green are ground.
- Gibson: Black and white are hot, green and red are ground.
- Jackson: Green and red are hot, white and black are ground.
Plan of attack. I decided to install a CRL 3-way switch, a high-quality unit you can get from such luthier suppliers as Allparts and Stewart-MacDonald. (Oak Grigsby and Switchcraft are two other excellent brands.) Though they cost a few more bucks than cheapos, good switches will give you much longer service and are well worth the investment.
After gathering your tools and supplies (soldering iron, 60/40 solder, 12-gauge stranded wire, hemostats, and a medium-tip Phillips head screwdriver), unscrew the control plate, flip it over, and eyeball the existing 3-way switch. Remember to place the screws in a small box so you don’t lose them. Plus, you don’t want a wayward screw to end up under the guitar because it will scratch the finish.
Tip: Before you unsolder and remove the switch, draw a diagram of how it’s wired. Even if your new switch comes with a diagram, it’s a good idea to document where each wire is attached on the original one.
Fig. 1
The old switch in this guitar used the traditional Fender wiring, so my diagram looked like Fig. 1. This is the standard Tele configuration.
Fire up the iron. The next step is to unsolder the two pickup wires from the blade switch. On a stock Tele with single-coils, there should be one lead wire to remove for each pickup. When soldering or unsoldering a wire, grip it with a pair of hemostats so you won’t burn your fingers! Once the solder is molten, give the wire a gentle yank to pull it free.
In addition to the pickup leads, there’s one wire that connects the output of the switch to the input of the volume control. Unsolder this wire from the switch only. In all, there are three wires to unsolder from the switch.
Detach the old blade switch. Next remove the two mounting screws that fasten the original switch to the control plate. Typically these are Phillips head screws, but some guitars require a small flathead screwdriver. The blade switch should drop right out of the control plate.
If you have a guitar with an inexpensive “box” switch, confirm that the mounting holes line up properly for the new switch you intend to install. Some imported guitars have different hole spacing than U.S.-built models for mounting the switch onto the control plate. If that’s the case, you’ll either need to get a new box switch or swap out the old control plate for a new one with hole spacing that matches an American CRL switch.
Photo 2
Photo 2 shows the CRL switch I’m about to install. Take a moment to compare it to the wiring diagram. Use the spring to orient yourself with the various lugs and their functions.
Install the replacement switch. CRL switches come with mounting screws, and you can either use them or the screws from the original switch, assuming they fit. Mount the switch on the control plate, then insert and tighten the screws.
Note: You can install the switch oriented in either direction, but sorting out the wiring will be easier if the new switch is oriented the same way as the original. In other words, if the spring on the old switch was facing the pickups, then mount the new switch that way too.
Wire up the new switch. There are four lugs for attaching wires on each side of the blade switch, making a total of eight lugs. For this classic Tele scheme, we only need to solder three wires onto six lugs. Each pickup lead will have its own dedicated lug. The other four lugs will be used to join both sides of the switch and connect the switch to the volume pot.
Before you begin wiring, review this simple breakdown of the switch while comparing it to the diagram. Each number represents a different lug on the switch. Next to the lug number is a description of the wire you’ll need to solder.
Spring side of the switch
1. Output wire to volume pot
2. Connects to prong #1 (switch output)
3. Unused
4. Lead from neck pickup
Non-Spring side of the switch
1. Lead from bridge pickup
2. Unused
3. Connects to prong #2 on the spring side of the switch to join both sides
4. Connects to prong #3 (non-spring side)
Tip: Unsure of your soldering skills? Check out “Soldering 101: A Step-by-Step Guide.”
Photo 3
Solder the leads from the pickups to the blade switch, and then add a jumper wire to connect both sides of the switch to its output lug. For the jumper, use a piece of 12-gauge stranded wire. Be sure to “tin” the entire wire before you solder it onto the switch. Tinning the jumper will make it easier to solder the wire in place, and you won’t need much additional solder. Finally, solder the wire from the volume pot’s input lug to the output lug on the switch. Photo 3 shows the CRL switch with the completed wiring.
Test drive. Now it’s time to button up the Tele. Flip over the control plate and re-install the screws to secure it. (Aren’t you glad they’re in that little box?) Now you’re ready to test out your work. Your Tele should have the classic switching configurations:
• Position 1: Bridge pickup only
• Position 2: Bridge and neck pickups
• Position 3: Neck pickup only
If everything is working correctly, slap on a new set of strings to celebrate the completed project and get ready to enjoy your new switch!
Intonating a flattop 12-string with a straight bridge saddle involves filing unique break angle and intonation points for each string—an operation that requires skill and patience. Let’s investigate and see exactly what’s involved.
We’ll use a beautiful 1972 Martin D-12-20 as our project guitar. The guitar was in good shape when its owner brought it into the shop, but it didn’t play even remotely in tune and the action was uncomfortably high. Many old 12-strings require a neck reset (an expensive proposition), but I checked the neck angle and it was fine. Fortunately for the guitar’s current owner, the problem was rather simple. Somewhere along the line a previous owner or tech had installed a saddle that was both too high and incorrectly radiused (Photo 1).
My job was twofold: lower the action by reshaping the bridge saddle and then intonate each string. I knew that once I completed these tasks, the D-12-20 would play better than ever and sound more in tune at the higher frets.
Requisite tools. To intonate a 12-string, you need a few specialized luthier tools. These include a string action gauge, radius gauges, and a radius block (the latter must match the fretboard radius). You’ll also need a mechanical pencil, a capo, self-adhesive 80-grit and standard 400-grit sandpaper, and flat, single-cut miniature needle files.
You can estimate where each string should rest on the saddle, but it’s nearly impossible to get it perfect on the first try.
Preliminary check. Before starting this kind of work on a guitar, it’s important to tune to concert pitch and take measurements. These specs provide a baseline to help gauge your progress. You’ll be taking several measurements, so write them down as you go.
First, put a capo on the 1st fret and measure action at the 12th fret with a string action gauge. Take this measurement for both the 1st and 11th strings—the first of the doubled high Es and the low E string. (We’ll assume your 12-string has the standard octave-string configuration, i.e., the octaves in each pair are closer to you than their wound partners. Some electric 12s, notably Rickenbackers, reverse this order.) Measure the distance between the bottom of the string and the top of the 12th fret.
Next measure the relief: With the capo still on the 1st fret, hold the 11th and 12th strings down at the 14th fret and measure the greatest gap between the bottom of the 11th string and the top of the frets. Typically this occurs around the middle of the fretboard, somewhere between the 7th and 9th frets. You can identify this gap by tapping the 11th and 12th strings against the frets while still pressing them down at the 14th fret.
Now remove the capo and check the action at the 1st fret.
Finally, using a strobe tuner, check the intonation for each string. (Naturally, this is tricky on a 12-string because you have to pluck each individual string of the six pairs.) Starting with the 1st string, play the 12th-fret harmonic—make sure it’s in tune—and then fret the same note. If the fretted note is sharp or flat compared to the reference harmonic, write down how many cents it’s off and in which direction. Repeat the process until you’ve documented the intonation at the 12th fret for all 12 strings.
Our 12-string’s preliminary specs. Here’s how the D-12-20 measured up: The action at the 12th fret was 6/64" for the 1st string and 7/64" for the 11th string. Too high to play! The relief was .012"—perfect for my client’s playing style. At the 1st fret, the 1st string was 1/64" and the 11th string was just over 2/64" above the fret. Again, perfect action at the string nut. At this point, I knew my job would simply entail lowering the action at the bridge saddle.
When I checked the intonation with a strobe tuner, and compared the 12th fret harmonics to their corresponding fretted notes, I found most of the fretted notes were from two to six cents sharp, although the G and D pairs were flat by about three cents.
With these measurements in hand, I was ready to get to work.
Photo 2
Sanding the bridge saddle. My next step was to check if the saddle’s radius matched the fretboard radius. My radius gauge revealed what I’d suspected—it wasn’t even close. The fretboard had a 14"radius (Photo 2), but the bridge saddle was around 8". This meant the saddle had a much more pronounced arch than the fretboard. I knew if I didn’t reshape the top of the saddle to match the fretboard, the D and G pairs would be radically higher than the other strings.
Photo 3
Using a 14" radius block and self-adhesive 80-grit sandpaper, I sanded the top of the saddle until it matched the block’s radius. Here’s the most accurate way to reshape the top of the saddle: Place the radius block in a vise with the radius side up and affix the self-adhesive sandpaper to the block. Now remove the saddle from its bridge slot, turn it upside down, and gently sand its top in the block’s concave area. If you shine light behind the saddle, you’ll be able to see how much material you’re removing from the saddle and make sure its radius matches the block (Photo 3).
Since the action was pretty high on our 12-string, I removed about 1/32" from the top of the saddle at both E string pairs. I removed quite a bit more from the middle of the saddle to flatten out the arch.
Once the saddle is correctly radiused, slip it back into the bridge and grab your mechanical pencil.
Photo 4
Marking the saddle. Now it’s time to draw guidelines on the saddle crown for both the individual intonation points and the various angles needed to guide the strings as they emerge from the pin holes (Photo 4). But before you start drawing lines, let’s take a moment to discuss where the strings should sit on the top of the saddle. First we’ll deal with the intonation points, then the string angles.
Fair warning: Setting the intonation entails some trial and error. You can estimate where each string should rest on the saddle, but it’s nearly impossible to get it perfect on the first try.
For this task, it’s helpful to mentally divide the 12 strings into three groups:
• The six E, A, D, G, B, and E strings you’d find on a regular flattop. We know the lowest four are wound, and the top two are plain. So far, so good.
• The plain octave strings (E, A, D, G) that pair with the wound E, A, D, and G strings.
• The doubled unison B and high-E strings. Just like their mates, these are plain.
Okay, think about the first group—our standard 6-string. As a general rule, both the low E and B strings intonate best at the rear edge of the saddle (closest to the bridge pins). The G string’s intonation point is typically at the very front of the saddle (closest to the soundhole).
That leaves the high E, D, and A strings to be accounted for. The high E will typically fall between the B (remember, that’s at the rear of the saddle) and the G (at the front of the saddle). The D and A strings usually create a stair-step pattern between the G and low E strings, with the D closer to the G, and A closer to the low E.
The four plain octave strings are a different story. Both the low E’s octave and the G’s octave points will be at the front of the saddle. The octave strings for A and D will be further back toward the bridge pins.
As you’d expect, the unison B and E strings sit at exactly the same point as their siblings.
Now consider how each string travels from the pin hole in the bridge to the top of the saddle—the intonation point. On this Martin, the six primary strings—those that correspond to a standard flattop—are set back toward the rear of the bridge. The six additional strings, the four octaves and two unisons that make a 12-string such a beautiful beast, emerge through the soundboard and bridge right behind the saddle.
On the rear of the saddle, you need to file individual angles (think of them as ramps) that allow each string to reach its intonation point without encountering a sharp edge. Correctly filed angles minimize string breakage and maximize sustain. The angle for the primary strings will be shallower than the six extra strings.
Photo 5
On the rear of the saddle, you need to file individual angles (think of them as ramps) that allow each string to reach its intonation point without encountering a sharp edge. Correctly filed angles minimize string breakage and maximize sustain. The angle for the primary strings will be shallower than the six extra strings.
Filing the saddle. This is where your inner artist gets a chance to shine. Using a miniature flat file, carve each string’s intonation point and rear angle, based on your markings (Photo 5). Go slowly, and to prevent any sitar-like buzzing, be sure each string leaves the saddle from a crisp, defined peak as it heads toward the soundhole.
Checking intonation. As I mentioned earlier, there’s a lot of trial and error involved with intonating a 12-string. Once you’ve done the first pass of filing, put on a fresh set of strings, tune them to pitch, and check the intonation.
Photo 6
The goal is to have the fretted note at the 12th fret match the corresponding 12-fret harmonic. Use a tuner to keep track of how close the fretted note comes to its reference harmonic. If the string frets sharp, file the intonation point back toward the rear of the saddle. Conversely, if the fretted note is flat, carve the intonation point forward toward the front of the saddle. When you’re done, the saddle should look similar to Photo 6. Don’t be dismayed at how many times you’ll need to slacken and remove the strings, file the saddle, restring, retune, and recheck the intonation.
Wrap it up. When you’ve got the intonation dialed in to your satisfaction, take off the strings one last time, pop out the saddle, and then polish it with 400 grit sandpaper, followed with a polishing cloth. Restring, retune, and you’re good to go.
This process takes a long time to master, but in the end, it’s worth it when your 12-string plays in tune all the way up the neck.