Raster Controls - IBM 3279 2A Maintenance Information

3279 MIM
2. Turn the FOC2 control fully counterclockwise.
3. Adjust the 'FOCUS1' control for the sharpest
image in the center of the screen.
4. While examining the upper right corner of the
screen, turn the FOCUS 1 control slowly
counterclockwise.
[f
the focus in the corner
improves (ignore the center). the FOC2 control
will improve the overall focus.
5. Turn FOC2 one eighth of a turn clockwise.
6. Adjust the FOCUS 1 control for the sharpest
image at the center of the screen.
7. Repeat the three prev:ious steps until there is no
improvement.
S.
If
the last movement of FOC2 made the focus
worse, tUTn
it
back one eighth turn to its
previous best setting and readjust FOCUS!.
9. Press the following keys: CONTROL C
Verify that the focus on green is good.
to.
Press the following keys: CONTROL 0 Q
(alphabetic)
12.
Verify that the focus on' blue is good.
and FOC2 a little to achieve a goud
compromise between the focus of the red, grc;cn,
and blue images.
Finally inspect all three colors and verify that
an optimum focus setting has been achieved.
Key in: (alphabetic)
a. Green: CONTROL C.
b. Blue:
c. Red:
CONTROL C CONTROL
0
Q.
CONTROL C CONTROL 0 l.
Alignment Mask
PIN 4423472
EC394472
Width and
Horizontal
Centering
242
mm
19.5
in.}
Figure 5-3. CRT Alignment Mask
Chapter 5. Display Adjustments 5-6
5.3.5 Raster Controls
Note: The
raster controls may be set accurately only
when the display is online, that is, converged, and
viewed from a normal operating position.
I.
Set the Normal/Test switch to Normal.
2. Hold down the AL T key, press TEST, release
both.
3. Jumper C2G06 to D2JOS (ground). Characters
will fill the screen.
4. Attach the alignment mask (Figure 5-3) to the
CRT face.
5.3.5.1 Raster Centering/Size Controls
Figure 1-4 shows the location of the controls
referred to in the following steps. If any of the
following controls has insufficient range to produce
the desired adjustment, set it as nearly as possible
and continue.
1. Adjust the top margin (TOP MAR)
potentiometer until the top character row is
centered in the top space on the alignment
mask.
2. Adjust the WIDTH and horizontal centering
(H CENT) potentiometers until the vertical
edges of the images arc correctly aligned.
3. Model 2 only Jumper C2J04 to D2DOS
(ground). (Disable interrow skip.)
4. Adjust the HEIGHT potentiometer until the
bottom trace of the last character row above the
divider line centers on the HEIGHT space (for
the correct model) on the alignment mask.
5. Model 2 only Remove jumper C2J04 to
D2DOS.
6. Adjust the 'SKIP' potentiometer until the bottom
trace of the characters in the Operator
Information Area is centered in the SKIP space
of the alignment mask.
7. Repeat from the beginning of section 5.3.5.1.
until the picture height and interrow gaps are
correct.
8. Remove the alignment mask.