Fixing a faulty pickup selector lever

And a few oddball pickups from the Duncan archives
A gauss meter showing pickup polarity readings of south (left) and north.

When I use the pickup  selector lever switch on my Fender Strato-caster, one of the pickups cuts out. What could be the problem?

There could be a few problems with the switch or contacts. Get a can of contact cleaner and lightly spray the contacts. This should remove any oxidation. Switch contacts can bend or loosen, especially when the control plate is removed and replaced. And hookup wires can snag, bending the contacts and making them work intermittently, which can be annoying.

I’d suggest taking the switch to a qualified repairman to tighten the grommet holding the contact lugs in place. These can loosen, allowing the contacts to move and become intermittent. Proper tools should be used to perform the job.

I often repair broken lever switches, so I can use the original switch in the vintage instrument, thus retaining its value. Old Centralab 1452 lever switches used in the early Fenders are hard to find, and very valuable. It’s important to keep the switches in good shape – not thrown in a drawer or bin. Keep them in a container that’ll protect the contacts from getting bent. I’ve seen early switches with the sweeper blade completely wore through the contact, making it necessary to replace the contact.

What are the characteristics of industrial phenolic sheets used on pickup and guitar parts?
Phenolic comes in various styles and colors and is great for making pickup tooling templates and fixtures. There are various grades of resin and base materials (see list).

Phenolic rod can be used for position markers and side dots similar to those on maple Fender necks. Phenolic sheet can be used for Telecaster and Esquire pickguards and, when sprayed with black and clear lacquer, look close to the real thing. Phenolic tubing can be used in bobbins and tapped for various thread sizes. I often use phenolic rod tubing when restoring old National lapsteel bobbins. There are many great applications, including making tooling templates and jigs.

I often use linen phenolic because it lasts longer when I’m using router bits with roller bearings. Linen works great when I make a prototype bobbin because I can cut out several using the simple routing fixture. When I get into larger runs, I draw the part and submit it to one of my fabricating houses to have it punched out. I also use it to make pickup blanks with a variety of pole spacings. A great source is The Thomas Register, which can be found in most libraries.

When Fender would pickups, did they insert the magnet wire into the eyelet before or after winding?
Leo and George Fullerton once told me the magnet wire was inserted into the eyelet before the pickup was wound. If you look at early Broadcasters, Esquires, Telecaster, No-Casters, Stratocaster, Duo-sonic, Precision Bass, Jazz Bass, Jazzmasters, and Jaguars, you can see the wire is wrapped in and around the edge of the vulcanized fibre several times. This helped support the wire as it was being hand-wound. It would take extra time having to tape the beginning wire to the underside of the bobbin and then later attach it to the hookup wire and eyelet and would be a waste of production time. The heat from the soldering iron was enough to melt the insulation within the eyelet hole as the solder was being introduced. The thermal rating of the Plain Enamel and Formvar magnet wire is 105 degrees C. If the beginning and end of the wire were mechanically stripped, there could be a higher risk of breakage.

Seth Lover also once told me that when pickups are mechanically stripped using sandpaper, there can be a higher risk of magnet wire oxidation and mechanical breakdown after a period of time. Mechanical stripping also causes a higher physical weakening of the magnet wire, making it thinner and weaker at both ends – where you need maximum protection.

Trying to insert magnet and hookup wire at the same time can cause further weakening. Also, if you leave magnet wire loose and disconnected from the bobbins, they can get tangled with each other, causing loose turns (and breakage as you pull them apart). It’s best to insert the magnet wire into the eyelets before and after each coil is wound. It simply reduces the risk of wire breakage. The eyelets are soldered from the bottom leaving a small even mound of solder on the eyelet.

Seth said, “It doesn’t make sense doing all the extra work putting the magnet wire in the eyelet after the coil is wound, because that’s where it’s gonna end up anyway! If you tape the magnet wire to the bottom of the bobbin as it’s being wound, it can come loose and end up being wound inside the coil!”

A custom-made handpress for pickup flatwork. Oddball pickups from the Duncan archives; a four-pole mando unit, and one made for a custom instrument for Alex Gregory

The G string on my Fender Jazz Bass sometimes strikes its pickup polepiece, and it then shorts out. What can I do to fix it?
It sounds like the “hot” wire from the control is connected to the beginning of the pickup coil.
I like to connect the beginning wire of my single-coil pickups to ground in the guitar circuit. When it’s connected to the beginning of the coil, there can be several problems, one of which you describe. The beginning wire of a coil is wound (at times directly) in contact with the magnet rod polepiece. If the rod magnets are not properly insulated, either by tape or chemical solution, the wire can short out with the rod polepiece, especially at each end of the bobbin, where the most winding pressure is put on the magnet wire.

The beginning of the coil winding can put a strain on the magnet wire as it is pulled and wrapped around the bobbin. Having the beginning of the coil connected to the hot contacts on the controls can make the poles noisy if touched, and cause them to short out if they touch the grounded string. That’s why the Fender Mustang guitar has solid top covers, not exposed polepieces. It keeps the grounded strings and fingers from touching the polepiece so the pickup doesn’t short out when the slide switch is used to reverse-phase the two pickups.

The magnets on the bobbin of my ’54 Fender Stratocaster have a rough surface with minute pits, while those on my ’65 Strat are smooth. What’s the difference?
Early magnets (like those used in ’54) have a .197″ diameter, ’65 magnets have a .187″ diameter. Both years’ were sand-cast, but the ’65 magnets originally had the sand pits ground off to give it the .187″ diameter and smooth surface.

The smoother surface allows the rod polepiece to be easily inserted into the bobbins during assembly. I liked the rough surface for the vintage appearance and the tighter fit into the flatwork. The rough sand marks and pits are from the original cast marks when they were formed into long rods before being cut to the desired length. I like the larger magnets, too, as they broaden the magnetic field to the strings.

Every time I hand-wind a Gibson bobbin, the ends begin to flair. What can I do?
First, I wouldn’t hand-wind Gibson bobbins because the material and winding tension can cause bobbins to distort.
I like winding Gibson bobbins on a coil machine with adjustable traverse, tension, and speed. If you wind them too fast, too much tension, and no traverse control, you’ll have problems. Winding without a traverse can cause the coil to be wound too wide within the bobbin and eventually cause too much pressure on the inside walls and as the coil gets filled up, the ends flair. The traverse wants to get wider and wider and the coil gets more and more turns.

You need to eliminate the natural tendency to wind directly to both inside edges of the bobbin. Also, when winding humbucker bobbins, it’s best to wind them identically for maximum hum reduction.

Too much tension can cause the bobbins to flair with increased DC resistance and usually different readings in each coil. Winding speed can also cause the bobbins to flair with increased tension as winding speed increases, again making the DC resistance fluctuate over the place.

The outer walls of the bobbin need to be supported to reduce flair, especially when hand-winding. If the walls flair too much, the bobbins can even crack and split. I’ve seen this with older Gibson P-90 single-coil bobbins, where problems can occur as the plastic gets older and more brittle. If you need them rewound, it’s best to send them to a winder with proper equipment and experience.

I removed the covers on my humbuckers so I could get the pickups closer to the strings. But when I do divebombs with my tremolo, the strings get snagged on the edge of the bobbins. What can I do?
If you don’t want to snag the bobbins, put the covers back on. If they cause your guitar to feedback at high volumes, have them vacuum potted.

Covers are used for several reasons; to reduce mechanical damage to the coils and bobbins, and to reduce unwanted electrical interference. Covers are a part of the design that makes the pickups humbucking. You can expect damage when you can see the strings are loose and snagging on various guitar components and pickups.

If you do divebombs, use something to protect the heart of the instrument – the pickups. If the strings become loose with the use of a tremolo, you need protection. The coil winding around the exposed bobbins are very delicate – one snag into the bobbin can permanently destroy it.

I’m working on a new accessory to protect exposed coils. It will reduce snags when changing strings or doing divebombs, and damage from excessive picking and fingernails.

Seymour W. Duncan

How do you wind a pickup that won’t fit on a typical winding machine?
Most machines can do bobbins 3″ to 5″ long. But in the early ’80s, when I built the pickups for the Guinness Book of Records’ largest electric guitar, the pickups were 9.90″ long with a winding traverse was 1.299″ wide!

Obviously, I didn’t have a machine that could wind a bobbin that long, so I had to make a winder out of a variable-speed drill. I mounted the drill sideways on a holding device so the bobbin could be wound Top Coming or Top Going. I proceeded to hand-wind the pickup using heavy build 32-gauge magnet wire – it was three times larger than a standard Fender Strat pickup.

I made traverse guides to keep the end walls from flaring, used a foot control for the variable-speed drill, and cotton gloves to keep the magnet wire from burning my fingers as I controlled the winding tension and speed. The stiffer wire made it more difficult, with more pressure.

I’d suggest making the same kind of hand-fabricated winding machine. You can either judge how many turns to put on the bobbin using 42-gauge wire, or make up a counting device. Depending on the winding length and traverse, you can usually determine the maximum number of turns using a little math. Some machines wind coils of various length, and most can accommodate various bobbin sizes. But most do not accommodate traverse controls that guide the wire back and forth on the bobbin.

Is there a simple gauss meter to check the polarity on guitar and bass pickups?
See the photos of the small gauss meter, which can read polarity and field strength when the magnet is parallel with the pointer.

The photo on the left shows the dial is pointing to the left indicating South 50, which is pretty strong for a vintage Strat bobbin. The top of the bobbin with raised poles is facing the middle and bottom of the gauss meter. The photo on the right is a ’55 Strat bobbin that has a North + polarity of almost 40 Gauss.

What are some oddball pickups you’ve built in the custom shop?
I enjoy making all kinds of pickups such as the one pictured, which I made for Alex Gregory for one of his custom instruments. It’s featured next to a traditional vintage six-string Stratocaster bobbin. I used .422″ pole spacing and 13 Alnico rod polepieces. The pickup was hand-wound using a special winder and magnetized South using a custom made magnetizing tool. I had to use controlled tension while winding, as it pulled a lot of wire from the spool each turn. It took about 15 minutes.

The four-pole bobbin shown is made using a dogear P-90 style thermoformed cover. I eliminated the two outer polepieces to make a warm and full-sounding mandolin pickup. I worked on some of Tiny Moore’s Gibson mandolins with a similar pickup.

What’s a good tool for pressing magnets into the flatwork? Are they special punches?
We use several types of hand presses. I prefer hand presses over power presses, which can chip, crack, and distort flatwork. You can control the pressure on the magnets, and keep the material in the vulcanized fibre from tearing away when the rod magnets are inserted.

This tool was custom-made and can press all the magnets in at once. We can insert various types of tooling that helps align the magnets to the proper height when using covers or exposed coils. We use many types of spacers needed for the proper traverse or winding area when assembling bobbins.


This article originally appeared in VG September 2001 issue. All copyrights are by the author and Vintage Guitar magazine. Unauthorized replication or use is strictly prohibited.