How to Troubleshoot Guitar Wiring Problems

How to troubleshoot guitar wiring problemsWhen trying to find that mysterious buzz, logic is your most effective tool.

Sometimes you might find yourself with a ground / buzz problem. This can be a truly frustrating experience and really kill the fun of building your own guitar. But, it really doesn’t have to be such a nightmare. You just need to trace your steps; that’s really it. This is all just logic. The problem is there somewhere; you just have to find it.

Assumptions:

In order to get around the fact that I am not actually sitting next to you as you work through this problem, I have to make the following assumptions:

  1. You know what you are doing. By this, I mean that you know how to use a soldering gun, read wiring diagrams (at least basic ones), and you own and know how to use a digital voltmeter. You might be able to get away without the voltmeter, but you will need soldering skills and a soldering IRON. Never use a soldering GUN on your guitar because it can ruin your guitar’s pickups from an amazing distance. If you are not sure what you are doing, don’t be too proud to march on down to your local qualified guitar repair tech, and ask him to finish the job for you. Once they have done the work, you can always look under the hood and examine their handy work to see what you can learn.
  2. Your cables are in perfect working order, they’re of good quality, and they’re shielded.
  3. All of your pickups and your amplifier are in perfect working order. If the amplifier has a three-prong plug you have it plugged into a three-prong outlet.
  4. You are not standing near any large power transformers or fluorescent lighting, and none of the lighting in your home uses dimmers.

Home wiring and grounding as it pertains to audio equipment (including guitars and amplifiers) is it’s own article, but meanwhile, just be aware that the home is quite often the source of unwanted hums and hisses. Unfortunately, this also puts fixing the problem out of reach for many of us (e.g., there’s nothing we can do about the corner bar’s neon lights). The easiest way to determine if it is in your home is to try multiple guitars and/or amps.

OK, now that that’s out of the way, here are a few suggestions:

  1. Make 100% sure that you’ve soldered the ground wire to the ground terminal and the hot wire to the hot terminal. This is a very common mistake, and if you have mixed this up, all bets are off, and nothing will sound quite right.
  2. Make sure that the wires in your control cavity are not touching each other. For example, many Gibson humbuckers have two wire leads in which the ground is braided on the outside and totally exposed, which can lead to exactly that kind of problem. In other words, a strand from the braid can get loose and touch a conductor, shorting it out. But most single coil pickups have wiring that is shielded all the way to the tip, which is helpful. Regardless, make sure that there are no ground wires touching hot terminals, and vice versa. It often happens that even when you’ve done everything right, when you’ve put the pick-guard or tele control plate back in place, some exposed wires manage to touch, causing a ground or buzz.
  3. Are you 100% sure that you’ve wired the pots correctly? We have several of the most commonly used wiring diagrams right here at Humbucker Soup.
  4. Have you tried process of elimination? Simply wire each pickup directly to the main volume pot, bypassing the five-way switch. In doing this, you can first determine that all three pickups, as well as your pots, are fine. If you use this approach, you can deconstruct your wiring down to the most basic components, heck, even try wiring each pickup directly to your output jack. Trust me, if you take this kind of logical approach, you’re going to find the problem. Anything else is just guessing, and you might be up all night doing this.

Testing Guitar Wiring : Guitar Building & Repair

Some Common Wiring Problem Scenarios:

Everything Works, but the guitar squeals at minimal levels or with minimal gain.

Most likely, the main output wires are backwards. Open the guitar’s main output jack, and reverse the hot and ground wires.

Everything works when the pickguard is unscrewed, but when I screw the pickguard firmly onto the guitar body, the signal cuts out.

An exposed ground wire is touching one of the hot wires or the pickup selector switch. Check all your ground wires and make sure that they are properly wrapped with electrical wire and nothing is exposed.

Everything seems to work, but when I have my pickup selector switch so that two pickups are selected (an in-between position) the sound is really nasally, really weak and really bad.

The pickups are “out of phase.” Reverse the polarity of one of these pickups. Best to do it to an outer pickup (i.e. the bridge or neck position) because if you do it to a middle position pickup, it will just be out of phase with the other pickup that it is currently in phase with. Note that sometimes this results in an overly squealing pickup and sometimes pickups are simply out of phase and cannot be used together.

Things seem ok at first, but one pickup squeals a lot.

The hot and ground wires are probably backwards. Reverse the hot and ground wires.

My volume pot works backwards. When I turn it clockwise, it gets quieter, and when I turn it counter-clockwise, it gets louder.

The terminals are wired backwards. Reverse the way you have wired the two outer terminals. Leave the middle terminal as-is.

I have a humbucker pickup that should be dead-quiet, but it squeals and feeds back whenever I play with any amount of volume or drive.

If your pickup has a nickel cover, then most likely you are experiencing microphonic feedback. You can fix microphonic feedback by wax-potting it. You may be able to do this yourself, but note that it is something that will require its own article. If you’re in doubt, it may be best to have it wax-potted by a professional guitar repair technician.

When I turn my guitar volume knob down even just a little, the sound gets muddy.

This is not a wiring problem. This is the natural behavior of the potentiometer and it will happen with your Tone control as well. The potentiometer (or “pot”) leaks high end frequencies to ground relative to its value. A 250K pot will leak more high frequencies than a 500k pot and sound muddier. It isn’t heard when the Volume is all the way up because at that point the pot is (almost) taken completely out of the circuit. As soon as you reduce the Volume just a little, it opens the floodgates and begins leaking the high end. If the sound is too muddy for you, try a larger value pot, or try your hand at installing the Treble Bleed Circuit we have written about here at Humbucker Soup. This places a small capacitor between your middle and right terminals. The result is that more highs are maintained when turning your guitar’s volume knob down. This is a really worthwhile (and fairly inexpensive) modification that turns your Volume knob into a very useful tool.

Basic Guitar Electronics I – Volume and tone control

Summary

When I was younger I spent many many late nights pulling my hair out, trying to find out where buzzes and squeals were coming from. 99% of the time, it was something very simple that I had overlooked. Rarely was it a deep and mystical issue. I promise that you will learn from this, and each time you wire up your guitar, you will be better at it.

Just remember to be as logical as possible and retrace your steps. The buzz is in there; you just have to find it. Best to try removing as many variables as possible and isolating each component. You’ll be sure to find the buzz.