The upper housing is held in place by eight phillips #2 screws on the underside of the machine. Removing the four screws around the battery compartment is the most difficult step in servicing the robot.

The recess holes around the battery compartment, are 5.85 mm in diameter. The thinest old school #2 phillips I could find, has a shank diameter of 5.90 mm. Humm, did they do this on purpose to make working on these difficult?

Well, the easiest way I found to overcome this problem was to ream out the holes to 1/4 inch. I used the wrench from a tap and die set, an ordinary drill, and a drill collar; to carefully ream out the holes by hand.

If you don't have all that, you can use a regular drill. Be careful though not to hit the screw as the drill bit with strip it and make it very hard to remove. The factory sets these screws very tight and they are difficult to take out if they have not been removed before.