I tried the parallel 18v battery mod, which didn't increase volume or affect the scratchy blend pot as I hoped it would. Tip: Signal, Middle: -Battery (Black), Ring: Groundģ. I removed the plastic output jack that comes stock and soldered in a 3-prong Switchcraft jack in it's place. I soldered the red T-Pro pickup wires into the main red battery wire along with the preamp brown wire, and hum gone.Ģ. Here is the wiring diagram for the Epiphone Thunderbird Pro:ġ. There is room for another control pot but a hole needs to be drilled, carefully with a sharp bit. The preamp is too big to add another battery in the compartment unless some wood is removed. The volume has a 103 (.1uf) capacitor for treble bleed. Remove the pickup grounds from the blend pot, solder them to a black cable, cover with shrink tubing, and solder the cable to the volume pot. Both of the T-Pro pickups have an extra red wire on them that should be wired to the battery red cable, as they are indeed active pickups. This is shown in the schematic wiring diagram attached.Ģ. The Bass and Treble potentiometers were not grounded at the factory, they should be grounded in series to the volume pot. I re-wired it exactly as outlined in the following steps.ġ. I searched far and wide for these schematics due to the humming problem, note these schematics only apply to the Epiphone Thunderbird Pro IV and V.

Epiphone casino wiring schematic