Press [4]  and the display should read "[4] Ribbon OFF"
Press the [LOWER] button while pressing down on a point about 9mm from the left edge of the ribbon sensor.
Press the [UPPER] button while pressing down on a point about 9mm from the right edge of the ribbon sensor.
Press the [KEY MODE]  button while pressing down on the center of the ribbon sensor.
When the '*' mark is displayed on the LCD press the [UP] button and the '*' mark should change to a '<-> mark on the LCD.
When moving your finger along the slider from left to right the values should be
Left edge =0
Center =127
Right edge =254

Again if this does not occur you should re do the test, if you still cant get this to happen properly, either the ribbon sensor or some IC's need to be checked, so go visit your Roland service center.