Willkommen zu unserem Förüm, Kamerad!!!
I dutifully checked my 1969/70 Slothead all maho, my 1972 long scale maple neck and my 1975/6 short scale maple neck as well as my noughties Epi Elitist (unlike the regular model a very faithful reproduction) EB-3s and here are ze rezülts of ze Tshörmän jüry:
Position 3 is wired identically with all four of them which means: Turn either of the vol controls down fully and all sound is gone, alas! -no operation of a sole pup possible. But that is not to say that the vol controls are on/off and nothing else. Reducing either vol just a quarter will bring out the other pup in full force more, the signal becomes louder and more prominent, not as meek, no doubt cancelling out is reduced, actually a preferable sound either way in my book. Once you get past the quarter vol turn though the sound loses again and finally dies. Given that I did not fiddle with the electronics of any of them and their electronics look unfiddled with from previous owners to me, I'd say this is the way things are supposed to be.
Uwe