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Date : 08/06/99
Replacement of a picture tube
DATA 708
5
R9002120
R9002129
III. Picture tube alignment
Introduction Before starting the alignment of the new picture tube, the projector must warm
up for at least 15 minutes at a medium brightness and contrast.
If a set of three tubes must be replaced, it is advisable to start with the
replacement of the red and blue tubes first, and using the green as the
reference.
Proceed then with the replacement of the green tube, using now one of the
other colors tubes as the reference.
Apply an external crosshatch pattern at 15 kHz or use the internal crosshatch.
Align the optical and electrical focus of the tube.
Rotate the deflection yoke until the horizontal lines of the crosshatch are
levelled on the screen.
Tighten now carefully the screw of the gear clamp of the deflection yoke.
Center the picture on the CRT faceplate (refer to explanation 'Raster
centering').
Note: alignment of the stigmators will change again its position, if so, realign
raster centering.
A. Replacement of a complete
set of three tubes
- Adjust the 2-pole and 4-pole
magnetic rings on the CRT neck in
their neutral position (see illustra-
tion on next page).
- Select a source that will generate
a field of small dots and
crosshairs.
Preparation
- Proceed to quick optical lens focusing (please refer to the projector
installation manual).
C. Adjustments applicable
to the three tubes
In such case, the remaining tube can be used as the reference for
centering and positioning of the new tubes.
B. Replacement of one or
two tubes
Neutral position
4-pole rings
2-pole rings