Performance Power tools mitre saw?

wont get up to speed and one of the brushes sparks heavily. Swaped the capacitor, checked the brushes but no joy. Starts up OK but doesnt reach full speed. No burning smell but is taking a lot of power because the lights in the garage dim when the trigger is applied. I am using this in Spain where I now live but help here is non existent. Can anyone please help as the saw is needed quite a lot.