Blender and Brian,
No problems with the design of the 480B collective, your aircraft were just misrigged. On a properly rigged a/c, before start, with friction off, the collective will stay full down since the spring will be over center. Lift the lever a few degrees and the spring up-force comes online. With rotors turning the spring is still over center with full down collective, but once raised the spring balances the collective forces very well...when rigged properly.