Does anybody know anything about Roger Black treadmills ?

I was usimg my Roger Black treadmill and after about 20 mins it just stopped although the display was still on and still counting. I removed the cover and expected to find the belt broken but this was ok. The following day it ran for about 15 mins when it slowed then stopped again. With the covers off I could here what sounded like arcing and could smell a slight burning smell. I could see no signs off arcing etc on any of the components. The motor fitted is a Greenmaster GMD82-05-1B. I checked the motor brushes and there about 12mm long. Any ideas ????????