Hi I want to know on my nutribullet on the motor it makes funny noise and a weird burning smell then I found out there is like black powder like stuff around the motor or armatuer. When I further investigated, the brushes which ought to make contact with the armatuer were breaking apart when you touch it. The spring that makes up the brush was not that springy. I think heat over time is result of that. Therefore, I think I need new brushes for the bullet. Where can I get them to purchase?