I bought a really nice 3 rail MTH Allegheny. I am also getting some track. When you hook up the transformer do you on hookup to the middle rail and one outside rail or both outside rails?
Unless something has changed, (it has been a while for me), when you hooked to one outside rail, it fed across via a common tie to the other outer rail. If you have any way to check continuity, such as an ohm meter, touch one probe to each outside rail and see....
