IBM Personal Computer AT Manual To Operations page 390

14
While you watch the screen, turn your system
unit's power on.
15
Did the screen change from white to black as soon
as the system unit's power was turned on? (This
totally black condition may last only 13 seconds
r "
before the display changes again.)
YES Go to Step 16.
NO Have your display serviced. Be sure the
power cable is with your display.
9000-8 Test