IBM 3180 1 User Manual page 86

Make sure the Power switch is set to On. From the back
of the display station, look for the red and green lights
through the top front vent.
Red Light Area
Is the green light ON?
Green Light Area
Replace the display element.
(Go to Chapter 5.)
Does the alarm turn ON and OFF continuously?
Replace the logic element.
(Go to Chapter 5.)