This article is from the Model Trains FAQ, by Christopher D Coleman with numerous contributions by others.
As to repairing your transformer, if the wiper or a connecting
wire is damaged I would try to repair it, but if thesmain coil is
burned out it is not really worth the trouble, at least on
smaller transformers. (there are places toshave transformers and
motors rewound) In my experience a simple dial-on-a-box Lionel
transformer will runs$15 to $30, and a nicer one with whistle and
direction controls $40 to $60. The dollar a Watt, or VA,
usuallysholds true for 1950 or newer. This depends greatly on
who's selling it and how much money they want to makeson it.
 
Continue to: