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Diagrams 7-1
throu~
7-6 to locate the adjustments
specified
in the following procedu res. The following
equipment is required.
AI ignment mask:
Model 1 - PN 2577899 (Diagram 2-2)
Model 2 - PN 2565170 (Diagram 2-3)
Screwdriver (small blade)
SL T backpanel jumper
5.2. 1. 1
Brightness
Note: The Brightness control is the outer knob on the
OF F-PUSH switch.
Adjust as follows:
1. With Brightness control fully counterclockwise, no
image should be visible.
2. At full clockwise rotation, raster may become visible.
Image may bloom and become excessively bright for
comfortable viewing if Contrast control (inner knob) is
fully counterclockwise.
3. Set Brightness control at point that produces best
display image for comfortable viewing.
5.2.1.2 Contrast
Note: Test Pattern 1 or a customer program that contains
dual brightness fields must be loaded to properly adjust the
Contrast control. The Contrast control is the inner knob on
the OFF-PUSH switch.
Adjust as follows:
1. With Contrast control fully counterclockwise, contrast
between normal and bright fields should
be
approxi-
matelyequal.
2. At full clockwise rotation, contrast should be maximum.
Normal brightness characters may disappear from screen
if Brightness control (outer knob) is set at a low level.
3. Set Contrast control for comfortable viewing, with
desired amount of contrast between normal and bright
fields.
5.2.1.3 Focus
Adjust the Focus potentiometer to the point that produces
the sharpest display image. Observe
~Iosely
the characters at
the center of the screen and those at the edges of the
screen. Set the potentiometer where the best focus over the
entire CRT is achieved. The Focus potentiometer is on the
HV power supply.
5.2.1.4 Yoke
1. Place proper alignment mask in position against face of
CRT.
Note: Use mask PN 2577899 to adjust Model 1 display
stations and mask PN 2565170 to adjust Model 2 display
stations. The yoke shield must be on the yoke before
makin
J
the following adjustments.
2. Short together the three test pins on analog card. Use a
clip or bare wire. (Pins are located between CHAR
HEIGHT potentiometer and SWEEP INDIC neon.) This
jumper disables vertical deflection and produces a single
horizontal trace across approximate middle of screen.
3. Loosen yoke clamp and rotate yoke until horizontal
trace is parallel to, or coincides with, horizontal lines on
alignment mask.
4. Ensure that yoke is firmly seated against CRT bell while
maintaining horizontal alignment obtained in step 3.
5. Tighten yoke clamp loosened in step 3.
5.2.1.5 Magnetic Centering Rings
1. Leave vertical deflection grounding jumper (connected
in step 2 of paragraph 5.2.1.4) attached and the
alignment mask in place for this adjustment.
2. Loosen cone shield retaining screw, rotate cone counter-
clockwise until locking tabs disengage, and slide cone
back 1 to 1-1/2 inches to expose tabs on centering rings.
3. Using tabs on centering rings, rotate rings until hori-
zontal trace passes through geometric center of screen.
(Geometric center is indicated by crossed lines in center
of alignment mask. Vertical center is indicated by line B
on the Model 1 mask and by line D on the Model 2
mask. Horizontal center is judged by comparing ends of
trace to vertical lines at edges of mask.)
4. Reinstall cone shield.
5. Proceed to paragraph 5.2.1.6 (Model 1 analog card
adjustments) or to paragraph 5.2.1.7 (Model 2 analog
card adjustments).
5.2.1.6
Modell Analog Card Adjustments
The procedures described in the following paragraphs apply
only to the IBM 3277 Model 1 Display Stations. See
paragraph 5.2.1.7 for Model 2 analog card adjustment
procedures. These procedures require that the Model 1
alignment mask (PN 2577899)
be
positioned against the
face of the CRT.
Model
1 Horizontal
Width:
The
vertical
deflection
grounding jumper (connected in step 2 of paragraph
5.2.1.4) should remain attached during this adjustment.
Proceed as follows:
1. Adjust Horizontal Width potentiometer so that ends of
horizontal trace on screen coincide with vertical lines C
and E on alignment mask. When adjusted correctly, trace
should
be
6.4 inches ±1/16 inch.
2. Check to make sure that horizontal trace still passes
through geometric center of CRT (Line B). Readjust
centering rings as described in paragraph 5.2.1.5 if it is
necessary to move trace back through center of CRT.
3. Remove vertical deflection grounding jumper.
Checks, Adjustments, and Removals
5-7
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