I'm sure this subject is too simple for most of the Board members but I hope someone can straighten me out. We have an old (20 yrs+) train set with a "hobby transformer no. 6607. It has 4 leads to connect to the cord that goes to the track. They are the AC Access, two unmarked leads, then DC Track is labeled. 4 leads total.  All we want to do is plug the set in correctly and avoid hurting the transformer or train set either. Can anyone help? Thanks