Voltage irregularities in post war transformers

[dogdoc]

I have tested 8 or ten of my lionel postwar transformers when NOT connected to a layout and found a little voltage on the variable taps even when set to zero. It can range from 2 to 5 volts. It is often consistant from one model of transformer to another of the same model and output. When wired to a layout or track, they go to essentially zero when off as you would expect. What goes? Some induction of some sort? A good question for Bob Nelson or any electrical expert. After testing so many transformers of this vintage I do not think it is abnormal

[servoguy]

 Most likely, there is a carbon path across the insulator where the roller parks when the transformer is off.  This will be a high resistance when the transformer is off, but your voltmeter has a very high resistance so the carbon path resistance can cause the meter to read.  The carbon is coming from the roller.  If you want to get rid of the carbon, remove the cover and clean the insulator.

Bruce Baker

[dogdoc]

Why would they go to zero when wired to the layout? Why is it only when the transformer are not connected to anything? (stand alone).

[servoguy]

 Because the carbon path is a high resistance, and the layout is a low resistance, and so output voltage goes to zero, or so close to zero it looks like zero.

Bruce Baker

[dogdoc]

So this is pretty much normal then? I tested 8 or ten tranformers and they all did it to some degree. Thanks

 

dogdoc

[richhotrain]

servoguy

 If you want to get rid of the carbon, remove the cover and clean the insulator.

Bruce Baker

Bruce

I have had the same experience as dogdoc. 

How do you remove the cover on an old transformer like an American Flyer 1B or American Flyer 8B?

Rich