IBM 5155 Manual To Operations page 186

26
Is the screen white?
YES - Have the unit that the display was
attached to serviced.
NO - Have the display serviced.
27
Tum the Brightness control fully
counterclockwise.
Brightness Control
28
Does the intensity of the characters decrease?
YES - Go to the next step.
NO - Have the display serviced.
9000-10 Test January 1984