IBM 5155 Manual To Operations page 224

5
·Turn the Vertical Size control clockwise until the
black areas at the top and bottom of the screen
disappear.
If
one of the black areas disappears
before the other, continue to turn the control
until the second black area also disappears.
6
Adjust the Brightness and Contrast controls for
eye comfort.
bl
.
•
~
/
r
/ /
/
Contrast Brightness
Control Control
3-36 Color
Display