According to the diagram, the Servo 100 has a circuit breaker in it. Also it is a brushed motor so if the brushes are worn out,
it would fail to run. Also, I see there is a circuit board which I presume would contain some solid state components which
are responsible for speed control. Mine has a little LED light on it that lights up when turned on. Does yours have that and
if so, is the bulb lit? It could easily be a defective plug on the unit or cord possibly. Another thing to consider or look at
would be the switches and speed rheostat although that would probably get flaky before they failed completely. I had mine all
apart once because it quit but it has been a while and I don't recall exactly what the problem was.