o scale transformer 'starting ' voltage

The MRC Dual Power was designed & built in an era when 5-6 volts was the starting voltage for most O Gauge  3 rail trains. The Dual Power and the TAC 2001 were ground breaking for the time in that they both had the capability to start at Zero volts. Some erratic operation would be expected.

Funny, I see this occasionally with my Lionel Powermaster throttle and Lionel 135 brick. A little headlight action, maybe a wee speaker blip. Tiny. Not always. I use TMCC and 18V, but I ramp up the power "manually" to 18V with my CAB-1 rather that leaving anything on an 18V default, so the brick starts at baseline. Better on the equipment, fewer surprises from overlooked visiting conventional engines. So far as I know the Brick starts at 0 volts, at least nominally. I don't know if "good" transformers do that, but I believe that "proper" ones should, unless there is an application reason not to. I've never had any problems from the little blip.

Some PW stuff has started and run conventionally (of course) under my CAB-1/Powermaster/Brick setup at far more enjoyable speeds (read: slower) than they probably ever did new.  Didn't some of the PW transformers actually start at 6 volts or so? Some of those old Lionel zoomy locos were actually better than we thought.

The PM-1 Powermaster from off to full is 32 steps and will break down the incoming voltage among those steps, or about .5625 volts per step with a 18 volt input.

It also has a programmable stall/floor voltage, which you can use to mimic the stall/floor voltage of the typical postwar transformer at 5-6 volts which will eat up 9-10 steps of the available 32 if it has 18 volts in.

While the stall/floor voltage of the typical postwar transformer is 5-6 volts, some, like the 1033/1044/4690 have a second, optional lower range than the 5-16 volts used for the train, on these models it is 0-11 volts, all done in steps as taps on the secondary winding.

The electronic transfomers, like the Dual Power, TAC 2001, MW, CW etc don't have "steps" as the output is proportional to the setting of the throttle potentiometer.