Transformer voltage when off phenomena

I had a ZW that experienced the same thing; having a slight voltage at the outputs with the handles in the off position. I opened up the case and noticed that the rollers were not fully off the coil, but just touching the first winding. Nothing much you can do, as it does not cause a problem with running the trains.

Larry

dogdoc posted:

 I have read something on another forum about meters, having very high impedance ,measuring voltage capacitively  when coupled to an off transformer circuit. Can anyone explain this to me? Or offer another explanation? Thanks

And that's the exact reason you're seeing the voltage, you explained it yourself.

Thanks for the reply. John , could explain what’s being measured to me? I guess I do not understand the statement although I am glad to know it is normal. Measuring voltage capacitively?

thanks

It's just the capacitive coupling through the air to a high impedance meter input.  If you simply put a 10k resistor across the input to the meter, the effect goes away.

on mine i noticed that there was some "play" between the stem being turned all the way off  and the actual rheostat mechanism. In my opinion just worn out. i put a line switch on the 110V cord to shut it off. 

In my case the rollers are completely off the secondary coil. It is capacitive coupling as described above. I see it on every post war transformer I have tested. Attach the off transformer circuit to a load and, like magic , it is gone. The minutia of model railroading and electricity is interesting!

Fractional m.amp of voltage   

You could play with it; maybe trigger some toy logic module if you were bored enough.