Looks like no leads showing here. http://www.smallbearelec.com/Detail.bok?no=339
On the GGG page^, it looks like the secondary center-tap
, maybe could be used to get 6vdc, but you'd have to Rectify and filter and regulate again.
Instead, a 6vdc regulator could take an existing voltage and convert it to DC.
Never tried it.
Looks like a tap could be at the diode regulator, or at the 9vdc regulator output.
Tapping the 6v circuit at the same place the 9v circuit taps means you get as much current as the 6v regulator can handle [or the transformer], after means the 9v regulator gets the current of both the outlet taps and running the 6v regulator.
I'd test for need of a heat sink for sure on the 6vdc, it's got to drop more voltage, so more heat sinking might be needed.