The back of the vacuum ( mine is a 6500 sr) has a plastic cover there are 4 plastic tabs ( the vacuum side has male, the cover is female )
The tabs extend out of the cover towards the vacuum
The top two are approx 1.5 inches from the sides
The bottom Left tab ( from the back of the cover is in .5 inches )
the bottom right is approx 1.5 inches from the side.
Just use a small screw driver and pry carefully ( my vacuum had a nickel in the rewind mechanism)
johnny 5 fix it guy, January 2009