By life, Leo Fender was always a tinkerer in all aspects. As much attention was given to the construction of instruments and amplifiers, in terms of its materials and how these were put together, as well as its internals, i.e. its circuitry and wiring. For a full list of pre-CBS Fender patents filed for by Leo, one is referred to Richard R. Smith’s “Fender - The Sound Heard ‘round The World”, Appendix 3, pp. 293-295. But as an example, take a look at US Pat. 2,784,631 with the title “Tone Control for Stringed Instruments” and filed for on July 31, 1953. It describes a tone circuit where one of the 2 potentiometers acts as both a tone control as well as a shunt for the bridge (“lead”) pickup. By mixing in the higher harmonics picked up by the bridge pickup, one changes the tonal characteristics of the guitar. In the patent, a pre-production Telecaster is used which does not have a pickup selector. Although this circuit never went into production, it proves the point Leo took different approaches to make things better.

The Basses by Leo website, Ken Baker’s labor of love and low-ender counterpart to the Guitars by Leo (GbL) website, is a treasure trove of “G&L and BBE Wiring Diagrams, Schematics, and Other Documents”, focussed on basses. Also check out the “Technical Stuff” section on its homepage for some interesting mods. GbL itself has an “Instrument Manuals and Wiring Schematics” album in its Gallery with diagrams, schematics, and pictures of wiring harnesses including for guitars. G&L had a “G&L Schematics and Wiring Diagrams” page its old, now archived, website containing “GUITARS” and “BASSES” subsections. Some block diagrams have been included among the pictures for convenience, complementary to providing an (archived) link in the text.

The “Components” section contains a discussion of parts encountered in G&L wiring harnesses, including their manufacturers, part numbers, possible replacements, and availability in the G&L Online Store. Be aware it is heavily cross-referenced. A phrase often encountered is “treble bleed” used if a capacitor is placed in parallel with a resistor, typically a potentiometer. A resistor has a tendency to block high frequencies, a capacitor more the low frequencies, let alone DC-levels. Combining these 2 impedances allows an audio engineer to shape the preferred response curve.