Accessing the belt is a nightmare. Perkins changed the design in his subsequent Spiral Groove models.
It's a two person job. You insert a lever into the gap between the metal plates of the plinth and pry the plinth apart. It may not separate easily but it will separate. If you have really tiny fingers and a high level of dexterity you should be able to access the belt buried in a tiny circular hole.
From what you describe it's probably not the belt. I would focus on the power supply and its connections.