Wyse WY-60 Maintenance Manual page 127

DEFINITIONS
Before checking the display, make sure you understand the
following terms:
Bezel
Display
Linearity
Pi nc ushi
0
nand
Barrel
Distortion
Video Display
Alignment Pattern
BEFORE YOU START
The front-piece of the display case that
frames the face of the CRT.
The portion of the screen where the video
display alignment pattern appears.
A comparison of character height and width
ranges in the display. You can check both
vertical and horizont3l linearity by
comparing character height and width within
the display. True linearity results in
characters that are the same height and width
range everywhere. See Appendix A for
linearity tolerances.
Distortion that results if deflection is not
uniform at the raster edges when compared
with the center of the display. Scan lines
bowed inward are called "pincushion
distortion". Scan lines bowed outward are
called "barrel distortion".
A test pattern to measure display alignment.
Before you check the alignment, do the following:
1.
Turn on the terminal at least 30 minutes before you check
the display. This warm-up period settles the display and
gives you an accurate test pattern to measure.
2. Generate the terminal test pattern (see Chapter 4).
3.
Point the neck of the CRT toward magnetic north to minimize
the effects of the earth's magnetic field.
4.
Have the video display reticle on hand to inspect the
display.
D-2