THE GIBSON SB SERIES WIRING DIAGRAMS
Gibson SB-300 bass, Gibson SB400 bass
The controls and associated circuitry of the Gibson SB bass guitar series were quite simple. A master volume and tone, and two slide switches (on/off); one for each pickup. The pickups themselves are Gibson single coil units.The pickups are wired in series, the slide switches change the ground point by shorting across each pickup, selectively removing it from the circuit.
Both circuitry and pickups were identical to those of the SG-200, SG-250 and ES-320 six string guitars; one way in which the manufacturing cost of these guitars and basses was reduced.
Gibson part numbers from the 1971 part list are as follows:
- Part #13570 Pickup assembly
- Part #70024 Volume and tone pots*
- Part #19231 Tone Control Knob
- Part #19232 Volume Control Knob
- Part #70486 Switch
- Part #70251 Input jack
* Interestingly enough, many instruments (predominantly early examples?) including this 1971 SB-400 do not use part number 70024 (which are 500k pots), but part BA811-3701 (250k pots) with 1960s date codes. These are the same potentiometers that appeared in 1960s Kalamazoo KG guitars, no doubt old stock that was used up before part 70024 was introduced.