Sounds like you may have blown a fuse. I don't know about the helix t-stat but I do know that the Helix Basic, Super and DBS1000's all have internal fuses that sometimes go. In my experience if one system goes and you take it apart it's the fuse. New fuses cost around $1.50 to replace.

If you are ready to throw it out the it won't hurt to take it apart and check the fuse.

Corey