Guitar Repair in London

[Mark]

That's quite interesting Baz... Perhaps another Fender mystery.

Normally you would connect one end of the pot track to ground and the other end of the pot track to the pickup or switch output (if you had multiple pickups). Only the pot wiper would then connect to the jack tip. In this way the pickup is terminated with the same resistance, irrespective of the pot position. Since the load resistance (250k) is more than 10 times the source resistance, the log taper should produce a smooth volume control. A secondary benefit is Q (resonance) remains more or less constant, so you shouldn't get too much of a tone change with volume.

The circuit shown effectively loads up your pickup output to reduce the volume. Can you imagine switching your lights off by shorting out the supply! I would imagine the volume control would not be a smooth log taper, and since your terminating resistance changes with volume, Q will be far from constant.

In days gone by designers quite often threw away the rule book if something sounded good... But Fender literature was often suspect... perhaps on purpose! And Fender quality control wasn't always that great when it came to wiring, so looking at one or two guitars built around the same time could be misleading, even if they're in original condition.

Just some thoughts Baz. The bottom line is I have no idea how they were originally intended to be built... but, I guess if you keep the volume full up it makes no difference...

Mark

[Basil Henriques]

It's the standard way with Fender wiring, as far as I know it's their practise to wire the pot as a variable short to earth (and it does SLIGHTLY affect the tone).

Check out the other schematics at :-
http://www.juststeelguitar.com/pickups.html

That's why you see Telecaster players using three quarter volume, and claiming that that's the "Sweet Spot." Likewise with the Fender steel guitars, the accepted norm with pro players is to set the volume pot at about three quarters and adjust the tone control 'till it's just noticeable rolling off the highs. (At least in the world of Hawaiian and mainstream Country players)

On the Stringmaster type of Steel the blend pot is actually a VR on a centre tapped humbucker that's "opened out".
The neck section is wound "top going" and the magnets are orientated for North polarity. The bridge position section is wound "top coming" and with a South polarity. The sections are mounted along a common centre line parallel to each other and centred one and one half inches apart . The result is a humbucking arrangement with two opposite magnetic fields that oppose and cancel each other. The sound is unique, being somewhat treble-dominant, that blends well in most bands. This combination works exceptionally well for both the Hawaiian and Western Swing style of music..

[Mark]

Yes Baz, I'm aware of the technique. The Telonics FP-100 volume pedal has an input impedance setting preset just for this purpose. Looking at the drawings this guy has on his site, the Dual Pro is the only one with this arrangement, all the others are connected as I'd expect.

Mark