daya - April 2011 helped me with his idea!
It seems that the brush holder breaks off - ITS COMMON.
I cut a piece of compression spring off a larger spring. Small spring pushes down onto the brush. The spring was held in position/exerting pressure onto brush with a piece of flat metal strip secured with the existing screw. The jigsaw now works well and I now have speed control! Before the surgery, it only operated at top speed!
Peter M
June 2013