Get the Most from Your Guitar Tech by “Speaking Repairman”
LAST ISSUE WE talked about mechanical buzzing. This time around we’ll list some tips for troubleshooting unwanted electrical noises.
Almost daily, I am asked to diagnose electrical hum, buzz, or crackle. The first thing I do is narrow it down. Is it the pickups, or is it the wiring/shielding? Here is an easy way to tell: Touch any metal where you plug in the guitar (output jack or metal jack plate). If the buzz goes away, it usually means your guitar is in need of a good shielding— which is typically done with shielding paint or copper foil. Keep in mind, you should be able to touch the strings and have the same effect. If you touch your strings and the noise gets louder, there is a good chance your strings are not grounded (or they are coated, as some coated strings do not ground quite as well.) Just by grounding your strings you can bring down the hum. This is accomplished by grounding a bridge stud, a spring claw, or a trapeze tailpiece.
If you’re touching the strings or metal and you still have hum, I’m betting you have single-coil pickups. We all know that single-coil pickups have a different kind of hum that will not go away unless “bucked” by another coil. (Get it?) In the past, Fender, Music Man, and others have tried hiding a dummy coil on the guitar to cancel the hum. Most pickup manufacturers now make hum-cancelling versions of your favorite single-coils, and these pickups sound better than ever. There are some new inventions in the search for the hum-free single-coil sound. Ilitch Chiliachki came up with a unique product, which is also sold by John Suhr. He has embedded a coil into a Stratocaster backplate, a P-90 control cover, and a Telecaster pickguard to act as a hum-cancelling coil to your existing pickups. The system is tunable and, when set up correctly, has a very small effect on your sound and allows you to keep your stock pickups.
Two methods of shielding: The left side is copper tape, the right side is shielding paint. They both get the job done. I solder the seams of the copper and hardwire it to ground to assure a solid connection. To ground the conductive paint, I have a piece of copper tape under the paint that’s wired to ground.
Other potential sources of noise are your guitar’s volume and tone pots and output jack. Here’s an important tip for tightening loose, crackly potentiometers: To keep the pot from spinning and breaking off all the wires inside, be sure to turn the post to the full counter-clockwise position and hold it in place while you tighten the nut. Likewise, for the output jack you can use a flathead screwdriver to keep the loose jack from spinning while tightening the nut. If your output jack is staticky, roll some fine sandpaper up like a cigarette, and sand out the corrosion from the inside of the jack.
If you hear crackling when turning a volume or tone control, try cleaning them. Places like Radio Shack sell potentiometer cleaner/lube. Be sure it says “Safe for Plastics” so you don’t melt your pickguard or mess up your guitar’s finish. A small squirt in the pot, and then twisting the knob back and forth to work it in will most often do the trick. If you have a hollowbody guitar and can’t access the pot, Stewart-MacDonald sells a pot cleaning cap—a cool attachment that screws to the top of the pot and forces cleaner down from the top.
Hopefully these tips and tricks can give you a better understanding of these problems and how to discuss and remedy them.