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CM150/PV150
3-5
GM CHASSIS
SERVICING
GM DIRECTVIEW SERVICE CONTROLS
The service menu controls are limited to the G-2, focus,
vertical size, and horizontal size. There are controls on
the Tuner/IF/Audio Processor module but you will not
be able to access these.
The service menu is another part of the service
adjustments. Checking the service menu setup must be a
part of normal servicing. The sheer number of items
should not concern you as only some of them may
require field adjustment. All the remaining items should
be set to the recommended value or setting and not
changed.
Display Size Controls
VR2138 Vertical Size
- Adjust for 1/2" of overscan. Be
careful not to cut off the closed caption display video
area.
VR3249 Horizontal Size
- Adjust 1/2" of overscan. Be
careful not to cut off the closed caption display video
area.
G-2 and Focus Controls
G-2 Setup
- On the video output module short the pins
of SETUP connector(near connector 5F2). This will
disable the video drive to the CRT. Adjust the G-2 control
until retrace lines are just visible. Remove the short
from the SETUP connector for normal video operation.
Focus Setup
- Adjust as needed after setting G-2. This
will be affected by the setting of G-2. The setting of G-2
will also affect the tint (green to blue) of peak video
white.
GM PROJECTION SERVICE CONTROLS
The service controls are limited to the service menu,
G-2, focus, vertical size, horizontal size, yoke ring
magnets, and the convergence controls. There are
controls on the Tuner/IF/Audio Processor module but
you will not be able to access them.
Make checking the service menu part of servicing GM
projection systems. In addition to the items mentioned,
in the directview notes, the Projo Mode feature, of the
service menu, enables or disables the Projo Setup
feature on the customer menu. The Projo Setup feature
adds a horizontal and vertical centering offset to the
convergence drive of Red and Blue. This feature’s
horizontal and vertical settings must be centered before
doing convergence alignment.
If you have changed a CRT, the convergence module,
adjusted the mechanical focus of the CRT lens, or have
adjusted the size you may need to check the
convergence alignment. It is recommended that you
make the convergence alignment adjustments in the
following order:
Display size and lens focus
G-2 and electrical focus
Yoke for tilt and centering
Adjust convergence controls as required.
Display Size Controls
The size controls are located at the front edge of the
power supply/sweep module. If the projo has a VCR shelf
you must remove the panel, under the VCR shelf, to
access the size controls on the front of the Sweep/SMPS
assembly (there are several screws holding the panel).
Using a cross hatch pattern adjust R3227 horizontal size
and R2104 vertical size for 1.5" of over scan. If you have
mono scope test pattern (service pattern signal
generator VCR tape #892-53) adjust R3227 horizontal
size for 4.5 tic marks (left and right) and R2104 vertical
size for 4.0 tic marks (at top and bottom).
Vert. Size
Horz. Size
Front of Sweep Module
Set Main Size Pots First
R2104
R3227
Convergence G-2 Setup and Video Cutoff Jumpers
The CRT video cut off and G-2 setup jumper assemblies
are located on the left rear corner of the main module.
These jumpers are used to mute red, green, or blue video
individually and cutoff all video drive to the CRTs for G-2
setup.
SW2 contains the blue, green and red video mute (or
video cut off ) jumpers. All jumpers of SW2 must be in
the normal position for doing G-2 setup. SW1 is the G-2
setup jumper.
G-2 Setup
This procedure should
not
be done with direct light on
the screen or in a brightly lighted room. When you are
setting G-2 this sets the conduction point of the CRT.
G-2 is not used to set picture brightness level. Be sure
that all of the video mute jumpers (SW2) are in the
normal position. Having one or more of the CRTs in video
mute will cause G-2 to be set incorrectly.
To view only
one color at a time cover the lens of the CRTs.
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