Bosch GSS 280A orbital sander

[Senator]

My Bosch gss280a orbital sander has suddenly stopped running on full revs just runs slow and rough, this is the second one that's gone this way. I've fitted new brushes but still the same. Has anyone else had this problem?
Is it dead or repairable I'm wondering as I now have two of them in the same state.

 

[Myfordman]

Assuming everything turns freely including the bearing under the disc, then fi the machine is over heating with lots of sparking on the commutator, then almost certainly the armature is knackered.

If it runs cool but just roughly, the speed control module is possibly duff.

 

[Senator]

Would there be a speed module as this model has no variable speed control?

 

[Myfordman]

Apologies I was thinking it was the same model as mine which does have speed control.