Video Circuit - Hitachi H972 Service Manual

High resolution color display monitor
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3. Video circuit

Prior to the video circuit adjustment, all sync. and Deflection circuit adjustment must be completed. The monitor must
have been warmed up for more than 60 minutes. Video signal must be terminated with 75 and should provide the
correct voltage at the monitor end.
[Pre-setting before adjustment]
TABLE 3: OUTPUT OF DAC
Function
R Color
G Color
B. Color
R. BKG
G. BKG
B. BKG
Contrast
Brightness
Sub Contrast
Sub Brightness
ACL
C-Cont
Note 1) Color Analyzer : Minolta CA 100 or equivalent.
3.1 Cut off adjustment
(1) Receive a signal of 94A with a blank signal pattern. (Black video)
(2) Connect a high impedance voltmeter (more than 1000M) to the Screen terminal (G2) on the Video board.
Adjust the Screen voltage pot on FBT to see 600  5V .
(3) After the screen voltage adjustment is completed, fix the SCREEN VR(FBT) shown in Attachment A.
(4) Ambient light on the surface of the CRT should show lower than 20 lux.
(5) Adjust R, G & B, BKG to show the CIE coordinate of
X=0.3130.02, Y=0.3290.02 at 1.2 cd/m
If it looks difficult to obtain X and Y readings mentioned above, do the followings to obtain these numbers.
1) Reset Sub Brightness to 9Fh or 60h.
2) Reset Sub Brightness to CFh or 30h.
3) If the adjustment can not be done with 1) and 2).
 When the value shown below can not hight: Change the R827 to R82E.
 When the value shown below can not low: Change the R827 to R82D.
3.2 White balance adjustment (Color 2)
(1) Receive a signal of 94A with a 100100 mm window pattern.
(2) Set Brightness Control to the center (7Fh) and C-Cont to the minimum (00h).
(3) Adjust the light output to 80 cd/m
(4) Adjust the white balance of high light output by Green and Blue color adjustments to read CIE coordinate of
X=0.313  0.008, Y=0.329  0.008
(5) Adjust Contrast Control to read 3 cd/m
(6) Adjust Red and Blue BKG to read the same CIE coordinate shown in 3.2.(4)
(7) Adjust Contrast or Sub Contrast Control to read 80 cd/m
shown out range, go back to 3.2(4)
(8) Register the readings of R/G/B BKG and Color data (Color 2) to the microprocessor.
3.3 White balance adj
(1) Receive a signal of 94A with a 100100 mm window pattern.
(2) Set Brightness Control to the center (7Fh) and C-Cont to the minimum (00h).
(3) Adjust the light output to 80 cd/m
Color 2 mode.
(4) Adjust the white balance of high light output by R/G/B color adjustments to read CIE coordinate of
Pin No.
#16 pin
(I301)
#17 pin
(I301)
#15 pin
(I301)
#13 pin
(I301)
#18 pin
(I301)
#11 pin
(I301)
#12 pin
(I301)
#14 pin
(I301)
2
(24.6ft-L) at the center of screen by adjusting Sub Contrast Control.
ustment (Color 1)
2
(23.3ft-L) at the center of screen by adjusting Sub Contrast Control in
Output
FF (MAX)
FF (MAX)
FF (MAX)
0V (MIN)
2.5V (CENT)
0V (MIN)
0V (MAX)
FF (MAX)
7F (CENT)
7F (CENT)
7F (CENT)
FF (MAX)
2
(0.35ft-L).
2
(0.87ft-L).
2
(23.3ft-L) and then confirm CIE coordinate. If it
 22 

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