As A pilot I understood the Roots blower on the viscount was the same as the F27 . It was magnesium alloy. On the f27-200 the shaft was a light quill shaft designed to shear if the bearing picked up and yes we had the red light, but it would have been burning then. Im not aware of any f27 having a problem.
Yes they are basically the same component, also on both aircraft types installed in an area with no fire protection, and yes as you say about the light that is what I was saying earlier the light was added after RMI as they had to do something but it was not going to be much help really, and I am not aware of any serious problems with them after RMI.
The main difference of course between the F27 and the V800 is that on the F27 the blower is mounted in a vertical position where on the Viscount 800 it was mounted horizontally.
It was found at the time of the investigations that this was one of the main factors in the accident because the drain plug on the blower was installed in the wrong place thus not allowing the oil to drain away as the blower failed, something that would not have been so critical on an F27 because the blower is mounted vertically and the plugs are at the top.