IBM 5291 1 Operator's Manual page 64

7. Set the Power switch to On and listen for the alarm.
8. Model 1
If the screen is still blank, call your service representative and report a
blank screen. Also report whether or not you heard the alarm.
Model 2
If the screen is still blank, call your service representative and report a
blank screen. Also report whether or not you heard the alarm and if the
Power-on light is on.
Problem Determination Procedures 4-5