I'm looking for a TV show that I watched when I was a kid (2000s). It's not Sliders, Parallax, Spellbinder, or Stormworld.
It's about a boy who travels in a group with a girl and an old man (maybe a doctor or scientist), looking for some crystals-ish to fix a machine. They travel with a companion, who is a puppet. They use belts that if they take it out they leave that parallel universe.
In the end, the villain turns out to be the good guy, and the scientist who they are traveling with, the bad. They all take their belts to give power to the protagonist's, and defeat the scientist.