Repair manual

2-67
THEORY OF OPERATION
b. Beam Shaping
A capacitor in the horizontal output driver network blocks the dc current
through the horizontal yoke and provides S-shaping of the current wave
form. S-shaping compensates for stretch at the left and right sides of the
CRT. This stretch is caused by the curvature of the CRT and the failure
of the beam to follow that arc.
c. Controls
Refer to paragraph 1 in this Section of the Service Manual for a functional
description of the horizontal controls (CENTER and WIDTH) that are
used to properly size and align (horizontally) the CRT video display.
Refer to the Calibration and Adjustment Section in this Service Manual
for a detailed description on how the horizontal controls are used in
conjunction with the provided Digital Palette Test Software (Test
Diskette) to properly size and align (horizontally) the CRT video display.
7. Vertical Deflection
The Vertical Deflection circuit generates a vertical output pulse that deflects the
CRT beam vertically down one scan line at the end of each horizontal scan.
When the Vertical Deflection circuit on the Logic Controller P.C. Board
generates the vertical deflection signal (VDEFLECT), it is processed by the
vertical processor. This signal is applied via connector J9 to the input of the
vertical processor. The vertical processor generates a vertical drive pulse
capable of directly driving the VERTICAL YOKE. This pulse is used to
deflect the CRT beam vertically down one scan line at the end of each
horizontal scan line.
a. Beam Deflection
The vertical drive pulse from the vertical processor is applied to the input
of the vertical driver network. The output pulse from the vertical driver
network directly drives the VERTICAL YOKE causing the current in
the vertical yoke to increase linearly. This action deflects the CRT beam
to the bottom right corner of the CRT.
When the CRT beam reaches the bottom, the output from the vertical
driver network switches causing the current in the vertical yoke to reverse.
This action moves the beam up to its starting position. However, the