Gibson EB-1 Wiring Diagram
By request here is the wiring diagram of the EB-1 Bass as best as I can decipher.
Now, the control cavity of the EB-1 is rather compact and although there are few components, it is difficult to poke around in there to trace the wiring. For that reason, the wiring diagram attached should be used as a guide rather than being taken as fact. Electronics is my weakest link so I can't troubleshoot the schematics by reason & sight alone. The bass was built in 1957 and the components haven't been disturbed since that date so I don't wish to tug and move the original wiring too much.
The 2 large ceramic capacitors have values of 0.05 MF & 0.01 MF and these particular ones are rated at 400V. The pots have no value on them but Gibson used 500K for many of it's basses and I'm assuming these are the same value. Again, I'm not about to fiddle with the 'innerds' to measure the value at this time.
I checked out my Les Shatten Wiring Diagram books for an EB-1 but it wasn't included in his early editions. Perhaps he has included this instrument in more recent editions.
Les Schatten Wiring Diagram Books
Les Schatten Designs
A poor photo of the electronics cavity. (damn camera busted trying to turn the flash off!!#@%&!)
Hope this helps somewhat. If not, get back to me and I'll see if I can refine the schematics.
Jack Bruce probably played an unmodified EB-1. It is my understanding that the late Felix Pappalardi of the 60-70's band 'Mountain' had his EB-1 modified with different capacitor ratings and some other unspecified changes. Gave him that signature 'buzz saw' sound in conjunction with his Sun Amps. Check out his dedication page here.
(Caution - Quick rendering, may not be accurate)
Poor Quality Photo of EB-1 Electronics Bay