Odd type z transformer behavior

[Dobson]

I spent some time rewriting my layout this year to use buss lines. I put in a line for my #71 lamps (10 of them) and a line for my house lighting (9 houses).   Both of the buss lines share a common ground buss line. The ground buss line connects to the u post of the lamp post line.   I thought the grounds were tied together in the transformer. Now for the odd behavior. When I turn on the voltage that has the ground attached to it both buss lines are powered (lights to lamps ans houses are powered). When I turn on the other line that does not have a u ground hooked up nothing happens. When I run a ground to that line that didn't have one before it has the ability to turn on both lines as well. 

Any explanations for why this would happen?  I separated the line bc I wanted to minimize the voltage load to each post. I have run it for awhile and it doesn't trip or overload but I am a bit frustrated bc I soldered for awhile only to have the same result of the load on one line. 

[cwburfle]

The Lionel type "Z" transformer does have all of it's "U" terminals tied together as a comoon.
While your description does not exactly match the symptoms I'd expect to see, I'd check two things:

1 - is the common post you are using ok?  - The common posts are tied together by a metal bus bar inside the transformer. It is possible that the terminal you have selected has broken away from the bar. If you have a meter, disconnect the buss line and check for voltage between the specific terminal post you are using, and one of the "hot" terminals (A,B,C, and D). If you get a reading the terminal should be good.
If you don't have a meter, use a spare miniature lamp, and/or try a different post.

2 - Did you mix up the common feed and hot feed on your ground bus line?  (many of us have done this on occasion)

Hope this helps.

[Dobson]

Problem solved. Ground and hot inverted. I can't believe I did that!  Thank you for the quick solve. I was stumped.