Alignments And Adjustments; Main Board Adjustments; Rgb Cutoff And G2 Adjustments; Rgb Drive Adjustments - Zenith ZVM-131 Service Manual

7. Apply a white field on the entire CRT. This can be
done with a video source or, with a Z-100 or Z-100
PC computer, by using the Z-BASIC or GW-BASIC
command:
PAINT(O,O),,7
Disconnect 5A2 connector from the video output
board and measure for the following voltages at the
cable connector:
Pin 2 (BLUE)
Pin 3 (GREEN)
Pin 4 (RED)
+
3.5 VDC to
+
4.5 VDC
+
3.5 VDC to
+
4.5 VDC
+
3.5 VDC to
+
4.5 VDC
If the voltages are within range, proceed to step B.
If any voltage is not within range, replace the main
board.
B. Refer to Alignments and Adjustments in this section
to be sure that all alignments and adjustments have
been made.
9. If the monitor still has a problem, the CRT or video
output board may be defective.
Alignments and Adjustments
Instructions for the alignment and adjustment of the main
board, the sweep assembly boards, and the audio/video
sync board are provided in the following text.
MAIN BOARD ADJUSTMENTS
RGB Cutoff and G2 Adjustments
These adjustments should be made in a darkened room.
1. Tum each control (R2506-RED, R2516-GREEN, and
R2527-BLUE) fully counterclockwise (see Figure 5).
2. Adjust G2 on the sweep board (see Figure 6) until
the raster just appears.
3. Adjust each cutoff control until a gray raster appears.
4. Readjust G2 until the raster just disappears.
Servicing
RGB Drive Adjustments
Apply a white field on the entire CRT. This can be with a
video source or, with a Z-100 or Z-100 PC computer, by
using the Z-BASIC or GW-BASIC command:
PAINT(O,O),,7
Observe the screen closely and see if any red, green, or
blue tints are present. Adjust the appropriate drive (R2506-
RED, R2517-GREEN, R252B-BLUE) until the tint disap-
pears.
Vertical Center and Vertical Height Adjust-
ments
These controls (R341B-height and R2125-vertical center-
ing) should be adjusted under low-light conditions.
1. Tum the G2 control clockwise until a raster appears.
2. Adjust these two controls so that the top and bottom
of the raster are 1/2-inch from these edges of the
CRT.
3. Turn the G2 control counterclockwise until the raster
just disappears.
Horizontal Center and Width Adjustments.
Horizontal centering control R3441 (located on the main
board) and horizontal width LX3261 (located on the sweep
board) should be adjusted under low-light conditions. (See
Figure 6).
NOTE: Width selection must be made before attempting
these adjustments.
1. Turn the G2 control (located on the sweep board)
clockwise until a raster appears.
2. Adjust these two controls so that the raster is 1/4-
inch from the left and 3/B-inch from the right CRT
edges.
3. Turn the G2 control counterclockwise until the raster
just disappears.
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