[Boatanchors] My model train transfomer variac idea - comments

[Henry Mei'l's]

There seemed to be a misunderstanding -- the variable low voltage (0- about 30 Vac) is fed to 
directly to a separate  filament (or old fashioned door-bell) transformer's low voltage/filament secondary winding and will thus produce from 0 to >120 Vac (0 to >240 ) at the primary winding, depending on the setting of the control arm on the train transformer and the rated voltage of the reverse connected transformer's low voltage winding(s). 

This not  is a conventional series- connected  few-volt bucking/subtractive or additive configuration.

My point is that variacs can be expensive (at least on this side of the pond) and this is 
a  cost-free way of controlling low wattage gear if you happen to have one of these model train 
units and a filament transformer at hand.

(Some (most?) model train control units supply dc so the ac voltage output would have to be tapped
ahead of the rectifier(s).)

73, 
Henry OZ1UF / N2NR