Note: This is based on the SPS1-UW (use these instructions with discretion)
screwdriver: TORX size 10, small flat-head
1. All knobs can be removed by using a small flat-head screwdriver.I found the best way was to use a fulcrum to push the knob up with the head. A small cloth and a finger should work. Save the data wheel until the top cover is removed.
2. Use the torx 10 screwdriver to remove the top cover.
3. To remove the data wheel, use the fulcrum concept in step 1, slowly.
4. The LCD contrast is under the data wheel, use the small flat-head to adjust.
5. Use a can of compressed air (my preference) to blow out any dust and grime.
6. A lightly damp cloth can be used to wipe around all knobs, buttons, LEDs, and the screen.
Some have commented on using contact cleaner to loosen sticky buttons. I haven't done this, but use at your discretion.
Please feel free to comment, edit, or adjust this page.
For a pictorial version, see http://redmine.ruinwesen.com/projects/midi-ctrl/wiki/Opening_a_MachineDrum