vorez yes i can surely understand u
, hmm i dont have facebook lol, really because i dont have time to play with it. But still u can ask me here so we can share the ideas together with others too.
Mike do not worry i`ll try to explain to u, secondary will be "q to r" "r to s" where "r" is the center (GND) and there is 2 snubber, 1 is for secondary and another is for tertiary. 1 snubber will be at "q to s" and another will be "t to u". Winding instruction for the tertiary will be "t to r" and "r to s" where r is the center (gnd) together with secondary GND. They will be tight together and have same GND placement.
So i hope i can clear ur confusion here. Because tertiary will be dual rail which can provide +/-12 or +/-15 its up to u to use either 7812&7912 or 7815&7915.
regards
Azmi