G&L tech resources: Wiring harnesses


Even without the preamp of the F-100E, the pre-BBE passive F-100 is already a complicated beast. So complicated, it warrants its own “Instruction Sheet” to learn about all the options. The pictures of the wiring harness are for a 1980 F-100 Series II w/DFV, including the Instruction sheet it came with, and a 1981 F-100 Series I. The large black switch is the usual 3-position pickup selector. The other (small) black tip 2-position ALCO MTA306D switch is the so-called “Phase Switch”. When positioned towards the bridge, and with the pickup selector in the middle, both pickups are combined in-phase. However when this switch is pointing towards the nut, irrespective of the position of the pickup selector, both pups come on out-of-phase. The little red tip 2-way (C&K 7401) mini-toggle is the “Splitter Switch”, for which Leo filed a patent application on May 5, 1980, resulting in US Pat. 4,319,510. Towards the bridge the pups are in “humbucking” mode; towards the nut one is in “single coil” mode. With the “Splitter Switch” in “single coil” mode, one engages a 100,000pf (.1µF) capacitor to ground in the signal path for each pickup. This will drain some of the high frequencies to ground avoiding a shrill sound. And with the “Splitter Switch” in “humbucking” mode the same 100,000pF cap to ground is in series with a 2,200pF (.0022µF) cap, for an effective value of about 2,150pF total capacitance. Another interesting idiosyncrasy is that the bridge pickup bypasses the treble control, most noticeable when in-phase. The CTS 250kΩ Audio Taper potentiometer for the volume control has a 20pF ceramic treble bleed capacitor. The PTB circuit is unique to G&L and discussed in more detail elsewhere. Suffice it to say the CTS 250kΩ Audio Taper treble pot is in series with a 22,000pF (.022µF) cap to ground whereas the CTS 1MΩ Reverse Audio Taper pot has a 2,200pF (.0022µF) treble bleed cap. Check out this album in the Guitars by Leo Gallery for more information with the caveat the treble bleed cap on the volume pot is often incorrectly listed as 200pF instead of 20pF.

That same album also includes a picture of the rather plain looking harness of a 2007-2017 (passive) F-100, first introduced on the 2007 F-100 Return Edition. The 500kΩ Audio Taper volume pot actually has a 200pF treble bleed cap. The 500kΩ Audio Taper push-pull pot for the tone allows the humbucker to be split activating only the outside coils, i.e. closest to the neck and/or bridge, in single-coil mode. This potentiometer is in series with a 47,000pF (.047µF) cap to ground. As it turns out, that harness was based on the the one used for the (ASAT shaped) 25th Anniversary model in which the F-100 humbucker was reintroduced. Just no coil split.


F-100 (Passive)