Many thanks for your help! The only reason I'm thinking about an armature is because I damaged the top of it taking off the bearing some time ago. The brownish bakolite collar that fits over the top is also damaged but the unit still runs ok at one speed only, I think about 15,000 rpm based on the amperage draw. The soft start function is fine. I am not sure of the bakolite collar purpose other that to sense armature speed for the controller.
If the cost of parts exceeds the price of a new unit I am wondering about by-passing the speed controller and have the unit run at full speed without the soft start function.
Does anyone know how to bench test the controller?
Any comments? Regards, Garth McGill