From what I understand Valco made Supro for National and other brand like Oahu. I am not sure on all the details. This pickup turns up on many different brands of lap steels. The strings pass through a small opening between the coils and the top metal plate. The coils share the same magnetic polarity and achieves hum canceling by having the coils out of phase. Since no strings over lap 2 coils at a time the sound is not out of phase. The magnet or magnets (one is sometimes a piece of silver painted wood) are on either side of the coils and act as a spacer between the bottom plate and top plate. The magnetic field is unique and strengthened by the upper plate. The coils are made of what I call fish paper and are very hard to wind. On this pickup the pole piece insert was broken and we had to recreate it before winding the coil. We have seen a few different gauges of wire on these things and spoke to Lindy Fralin about it. He has rewound so many of these it is his opinion that they grabbed what was on the shelf and went to work. Both Lindy and Jason Lollar who has just come out with his reproduction of the pickups are amazing resources on pickup history and design.
|Putting on the wire, controlling the tension and scatter wind by hand.
Here we are using the StewMac/Schatten coil winder.
|The 4 metal clips need to be lifted to get to the coils|
|Here they are!|
|Looks like a kids project.
|Here is the rebuilt pole-piece housing.
Thank you Leo, you are magic!
|The magnets are on each side of the cover plate.
You can see how little room there is for the strings to pass through between
the cover plate and coils