Power Tool Repair

I have an old Bosch electric drill (CSB 420E) which has started behaving strangely: Its speed has dropped greatly, and it sparks so much I could turn the lights off and still see what I'm doing. I suspect a fault in the armature or field coil, but they both look OK. Brushes seem ok as well. Any ideas? I'm reluctant to junk it because I am too mean to buy a new one.

tech-king9 years ago
check for dirt or lack of lubrication if needed.