Testing Guitar Pickups with a Multi Meter.

 

How to Test Guitar Pickups with a Multimeter

Let’s talk about one of the most important subjects every guitarist needs to know in order to troubleshoot their electronics: testing pickups with a multimeter. These affordable hand-held devices are vital and helpful to have around. Whether diagnosing unwanted noises or verifying your pickups’ performance, a multimeter helps you get the most from your guitar and rig.

Here, we’ll look at a couple of popular ways guitarists can use a multimeter to test their electronics. We’ll also dig into pickup resistance, measuring potentiometers (pots), and how to check your instrument’s ground. By the end of this article, you’ll know exactly how to test guitar pickups with a multimeter.

First stop, pickup resistance!

https://youtu.be/e68QGkcJVxI

What is pickup resistance, and should you care?

*Pickup manufacturers generally list the resistance of a pickup in their documentation.

What is guitar pickup resistance?

Many believe that a pickup’s resistance directly correlates to its output. The higher the number, the hotter the pickup, right? Not necessarily. 

A pickup’s resistance is actually a measure of how hard the current has to work to get through the wire coils. 

But more windings (which usually means higher output) also means higher resistance. Therefore, people often equate the two.

In reality, it’s not that simple. A host of variables determines a pickup’s output. 

These include magnet material, gauss (magnet strength), wire material, and the number of coil winds. 

So, a pickup with a strong magnet can still have lower resistance and plenty of output. 

Likewise, another will deliver low output, yet yield a higher resistance.

A pickup’s resistance is only important when considering all these other factors. 

Therefore, measuring a pickup’s resistance is a diagnostic tool to help confirm your pickup’s health. 

It does not solely determine its performance characteristics and output.

So if your pickups’ tone seems off, grab your multimeter and let’s get to work.

How to test guitar pickup resistance

The first step in learning how to test guitar pickups with a multimeter is asking if you’re already happy with your tone. If you are, there’s no reason to dig into your instrument. 

But if not, there are two primary methods for measuring pickup resistance; from your guitar’s output jack and from the pickup lead wires. We’ll outline both processes here.

From the Guitar’s Output Jack

[TRY THIS FIRST]

1. Turn on your multimeter and set it to the “Ohm” or “Ω” setting (Ohms “Ω” is the unit of measurement for resistance)
2. Plug a cable (or lead for our European friends) into your guitar but leave the other end free
3. Set your pickup selector switch to the position of the pickup you want to check and turn the volume all the way up
4. Touch one multimeter probe to the tip of your cable’s free end
5. Touch one multimeter probe to the sleeve (part of the cable end below the tip section) of your cable’s free end.

After a moment, your multimeter should settle on a number. This number is the pickup’s resistance. Keep in mind; resistance is never exact. Therefore, the number will be around the pickup’s rating, give or take. If it’s not, it’s time to dig a bit deeper.

From the Lead Wires.

This method is perfect for checking the resistance of pickups not already installed in an instrument. It’s important to note that an installed pickup will need to be desoldered and removed from your instrument in order to test is using this method.

Testing Single-Conductor Pickups (all single-coils and non-splittable humbuckers)

1. Turn on your multimeter and set it to the “Ohm” or “Ω” setting
2. Touch one multimeter probe to either wire (Excluding the ground wire. More on that in a minute)
3. Touch the other multimeter probe to the remaining wire

As before, your multimeter should read out your pickup’s resistance. It may still vary a touch. 

But this method removes the rest of your guitar’s electronics from the equation and offers a more accurate reading.

Testing 4-conductor Guitar Pickups

Any humbucker that boasts five attached wires is a 4-conductor humbucker. 

The pickups get their name from the two wires extending from each coil. 

There is also one common ground wire. This wiring allows for selectable split-coil performance options to achieve single-coil-like sounds. 

4-conductor humbuckers are extremely common.

Testing the whole 4-Conductor Pickup.

1. Turn on your multimeter and set it to the “Ohm” or “Ω” setting
2. Connect the pickup’s red and white wires
3. Connect the pickup’s green and bare wires
4. Attach your multimeter probe to the black wire
5. Attach multimeter probe to the bare/green combo

The number on your multimeter is the pickup’s total resistance. 

If the figure is correct, the pickup is fine. But if it doesn’t, it’s time for the next step.

Testing each coil separately.

1. Turn on your multimeter and set it to the “Ohm” or “Ω” setting
2. Testing the fixed-lug north coil: Touch your multimeter probes to the coil’s white and black wires
3. Testing the adjustable south coil: Touch your multimeter probes to the coil’s red and green wires

The resistance of each coil should be roughly half of the full pickup’s listed rating. If one or both are off the mark, then you have a broken pickup.

But don’t worry. Seymour Duncan has plenty of replacement pickups for you. And we also re-wind and repair broken pickups.

If both are on the money, but a problem persists, it’s time to check the pots.

How to test Guitar Potentiometers

When it comes to guitar electronics, pickups are only part of the equation. Everything between them and your guitar cable plays a pivotal role in your tone. 

It can also introduce its own set of issues, especially volume and tone pots.

At their core, potentiometers are variable resistors. And because different pickups work best with different resistance, these pots are available in a few different ratings.

Most Common Guitar Potentiometer Ratings

• 250K: Single-coil Pickups
• 500K: Humbucking Pickups
• 1MOhm Jazzmaster, Some Vintage Teles, Fenders with Vintage Wide Range Humbuckers
• 25K: Active Humbucker

Finding a Pot’s Rating

Finding your pots’ resistance is often as easy as looking at what’s written on them. But not all pots are as telling. 

If the pot doesn’t have a printed rating, you can solve the mystery with a glance at your guitar’s technical specs. 

Still can’t find the info? Then whip out your multimeter, and we’ll take a look for ourselves.

1. Turn on your multimeter and set it to the “Ohm” or “Ω” setting
2. Attach each probe of your multimeter to the outer lugs on the pot

This method gives you the pot’s maximum value. You might notice that the value is rarely precisely the same as the pot’s rating. 

Again, resistance is never an exact science. But it is typically within 10% on either side of the expected value.

Linear vs. Logarithmic Potentiometers

And for the geekier among us – which totally includes us – you can also check if your pots are linear or logarithmic. 

Determining if your Pots are Linear or Logarithmic

1. Turn on your multimeter and set it to the “Ohm” or “Ω” setting
2. Turn the potentiometer to half-way through its range
3. Attach one multimeter probe to the left-most lug
4. Attach the other multimeter probe to the center lug

A linear pot’s resistance reading will be around half of its maximum value. Logarithmic pots will read substantially less.

Testing your Guitar’s Grounding.

What if your pickups and pots check out, but there’s still excess noise?

Then more than likely, you’re experiencing bad grounding. Luckily, it’s incredibly easy to diagnose. So, don’t accept defeat. Instead, give this multimeter test a try.

How to Test Your Guitar’s Grounding

1. Switch your multimeter to its Continuity setting
2. Touch your red probe to one of your guitar’s strings
3. Touch your black (ground) probe to your guitar’s output jack

A good ground will result in a clear beep from your multimeter. But if you don’t hear anything, you’ve found your problem. There’s a break in your wiring somewhere. 

Open up your guitar and check all of your solder-joints, ensuring they are all nice and solid. Once you find and fix the problem joint(s)…problem solved.

Multimeters are invaluable for all electric guitarists and bassists. They’re inexpensive and tell you a lot about your gear’s health. And though they can look a bit intimidating, they’re easy to use. 

So easy, it’s amazing what you’ll fix with just that and a good soldering iron. We hope that “How to Test Guitar Pickups with a Multimeter,” is a big help down that road.

Dealing with Snapping Guitar Strings

  Dealing with Snapping Guitar Strings

Nick Asks:

“I have an acoustic guitar and keep breaking brand new strings while I’m getting them tuned up to pitch. It’s always my high B string, and it always seems to break near the tuning peg as I’m tightening it up to pitch. Why does this keep happening?”

Hi Nick:

Believe me, I know how maddening it can be to break a brand new string during a string change, especially if you don’t have a good supply of Single Guitar Strings available to replace it.

Really, this shouldn’t be happening–certainly not very often. If you find that you’re constantly breaking the same string while tuning, and it’s always at the headstock-end of the guitar, then there’s usually some issue with the tuning post (the post you wind the string onto) or the nut (the bone or plastic piece the strings pass over on their way to the tuning posts).

It can be hard to tell for sure which one it is, because the spring-like action of a string that’s been wound onto a tuning post can make it difficult to tell exactly where the string snapped.

Most Likely Cause: A Sharp Tuning Post - 

It’s not uncommon for the hole on the tuning post–the metal post you wind your string onto–to have edges that are just sharp enough to cut a string as you tighten the string up to pitch. 

The thicker wound strings (low E, A, and D) are usually strong enough to resist those sharp edges, but the thinner unwound strings (G, B, and high E) are susceptible to being cut.

These edges can sometimes be sharp enough to cut your strings.

This issue can be fixed with careful use of a file to smooth-over the sharp edges. However, I recommend letting a pro do this rather than blindly taking a file to your expensive guitar–unless you’re really comfortable doing this kind of work (or simply don’t care if you screw up).

On the other hand, there’s also a DIY method that doesn’t involve a file. All you need is a piece of guitar string–preferably a thicker, wound string like a low E or A string. 

We’re going to basically use that piece of string in the same manner we’d use a file–using the winds of the string as little teeth to gently round-off those sharp edges.

Procedure – Using an Old Guitar String as a File

1. OPTIONAL: If you’d like, you can remove all the strings to give yourself more room to work, but it’s not totally necessary. If you do, it’ll give you a sacrificial low E string, which we’ll use for our procedure. That’s what I’ve done for this demo.

2. If you chose to remove all your strings, grab the low E and clip off a straight 6 – 8 inch piece from one end before you throw it away.

 Otherwise, you can instead use the non-ball end of a new string without actually clipping it off. For my demo here, I removed all the old strings (since they needed to be changed anyway) and clipped off the end of my old low E.

You can clip that curl off the end if you’d like

3. Turn the offending tuning post so that the holes are aligned sideways (not facing the other tuners) so you can get the angle needed to feed the piece of string through easily. In a moment you’ll see why this position is helpful.

Turn the tuning peg until the holes are aligned as shown.

 4. Thread your piece of string through the tuning peg and grab the other end with your other hand, like you’re holding dental floss and preparing to floss your teeth.

5. Bend the string around enough that it curves just enough to contact that sharp edge of the tuning post’s hole. 

Don’t bend it so much that it creases–you want it to remain rounded so it can slide easily.

You want the string’s windings to contact the sharp edge of the tuning post hole.

6. Now, gently pull the string back and forth in a sawing-type of motion, making sure the string’s windings rub against the sharp edge.

 You’re not trying to remove a large amount of metal here–you only want to gently and very slightly smooth-out whatever sharpness might exist and create a more soft, rounded edge. 

While you’re at it, you can do the opposite edge too. While in the same rounded position, simply shift the pressure to the edge of the hole on the opposite side.

7. Repeat this procedure for the other edges of this post’s tuning holes, since we’re not sure exactly which edge might be cutting your string during tune-up. Also, more than one edge might be sharp.

8. Carefully blow or dust-off any metal filings that might have fallen onto the headstock.

Once you feel you’ve sufficiently rounded all 4 edges of the tuning post’s hole, cross your fingers and string it up with a new string.

 Hopefully the new string won’t break now or in the future while you’re tuning it up. If it does, remove the string and repeat the procedure again–rounding those sharp edges just a little more. 

If the same string continues to break, it’s possible it’s not the tuning post, and the problem might instead have to do with the nut.

Other Possibility: Dirty or Misshapen Nut Slots

A guitar’s nut slots are the #1 thing that get rushed at the factory–especially on low and mid-priced, mass-produced guitars.

Even if your guitar’s nut did get proper TLC before leaving the factory, the bone or plastic it’s made of doesn’t last forever. So, over time normal wear-and-tear can take its toll. The slots can become misshapen and/or become dirty with grit and grime after years of use.

All these factors can lead to string breakage at the nut. Just as sharp tuning posts can act like little string cutters, dirty or misshapen nut slots can break strings too.

There’s no way I’ll be able to cover the topic of nut slot shaping in this blog post. What I can show you, however, is how to clean and lubricate the nut slot. 

That’s another easy, DIY thing you can do safely, and it just might be all that’s needed to stop those strings from breaking during tuneup (assuming the nut is the culprit).

Procedure: Cleaning & Lubricating Guitar Nut Slots

To clean and polish nut slots, I like to use a small piece of ultra fine sandpaper that is 2000-grit or higher. You can find small batches of these fine grits online or at hobby stores.

I bought this sandpaper kit at my local hobby store.

In this case, I’ll be using 2000 grit from a Sandpaper Kit bought at a local hobby store. I like 2000 because it’s abrasive enough to remove dirt and debris from the string slot, but not so abrasive that it’s going to modify the shape or depth of the slot (as long as I’m gentle with it).

Remember, my intention here is to show you how to simply clean out the slot, not physically modify it’s shape.

 1. Get a piece of 2000 grit sandpaper, and cut out a very small rectangular piece, as shown here.

Cut a rectangular piece that’s about 1 in. long by 1/2 in. wide.

 2. Fold the sandpaper in half lengthwise, but don’t put a hard crease in it by pinching the edge flat. Just fold it over and let it crease naturally. 

You can gently flatten it a bit if it seems too wide for the string slot, but try to avoid creating a sharp crease.

3. Insert your piece of sandpaper into the slot and gently rub forwards and backwards. 

You can also use a sharp corner to scrape inside the slot too if you feel it’s needed to get out stubborn gunk.

 Remember, you’re not trying to actually modify the shape of the slot here, so be gentle with your pressure.

Gently move the sandpaper back and forth. You’re just trying to clean, not modify the shape of the nut slot.

4. Once you feel you’ve got the slot nice and clean, remove any resulting bone dust or debris that might be inside the slot by blowing it out or sweeping it out using a small paintbrush.

5. Apply a drop of lubricant to the nut slot. My favorite product for this is Nut Sauce. I’ve used other products too, including graphite (shaved pencil lead), but none of them have performed quite as well as this stuff. 

It can be difficult to see the lubricant coming out, so I recommend putting a paper towel next to the slot to catch any excess.

Applying a bit of Nut Sauce. 

Final Thoughts

That’s really all there is to it. Now, string it back up and, assuming the nut was the problem and you did a good job cleaning and lubricating it, you shouldn’t have further problems with the string breaking. 

If you do, it’s possible there’s another problem–such as a misshapen nut slot. In that case, I’d recommend taking it to a pro and they’ll be able to easily reshape that slot so it’s not cutting your string.