Elekta CTR1498 Manuale - Pagina 9
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Stampa la paginaD. R-Y DEMODULATION
(a) Apply a SECAM color bar signal.
(b) Conned an oscilloscope to TP18 ( Pin 1 of IC1401 ).
(c) Adjust L211 to obtain an R-Y signal with correct chrominance output ( Fig. 8 ).
16. SUB-COLOR ADJUSTMENT
(a) Receive Philips signal.
(b) Set the contrast, brightness to the normal position, set the color to minimum.
(c) Turn VR801 clockwise until the color is not overflow.
1. COLOR PURITY ADJUSTMENT
Note:
Before attempting any purity adjustments, the receiver should be operated for at least fifteen minutes.
(a) Demagnetize the picture tube and cabinet using a degaussing coil.
(b) Turn the contrast and brightness controls to maximum.
(c) Adjust Red and Blue Controls ( VR403 ) and ( VR405 ); to provide only green raster. Advance the Green Bias Control ( VR404 ) if
necessary.
(d) Loosen the clamp screw holding the yoke backward to provide vertical green belt ( ZONE ) in the picture screen.
(e) Remove the Rubber Wedges.
(f)
Rotate and spread the tabs of the purity magnet ( See Fig. 9 ) around the neck of the picture tube until the green beil is in the
center of the screen. At the same time, center the raster vertically.
(g) Move the yoke slowly forward or backward until a uniform green is obtained. Tighten the clamp screw of the yoke temporarily.
(h) Check the purity of the red and blue raster by adjusting the bias controls.
(i)
Obtain a white raster, referring to white balance adjustment.
(j)
Proceed with convergence adjustment.
2. CONVERGENCE MAGNET ASSEMBLY POSITIONING
Convergence Magnet Assembly and Rubber Wedges need mechanical positioning following Fig. 9.
3. CENTER CONVERGENCE ADJUSTMENT
Note:
Before attempting any convergence adjustments, the receiver should be operated for at least fifteen minutes.
(a) Receive crosshatch pattern with a color bar signal generator.
(b) Adjust the brightness and contrast controls for well defined pattern.
(c) Adjust two tabes of the 4 Pole Magnets to change the angle between them ( See Fig. 10 ) and superimpose red and blue vertical
lines in the center area of the picture screen. ( See Fig. 11 )
(d) Turn both tabs at the same tiem keeping the contrast angle to superimpose red and blue horizontal lines at the center of screen. (
See Fig. 11 )
(e) Adjust two tabes of 6 Pole Magnets to superimpose red / blue line with green one. Adjusting the angle affects the vertical lines and
rotating both magnets affects the horizontal lines.
(f)
Repeat adjustments 3, 4, 5 keeping in mind red, green and blue movement, because 4 pole Magnets and 6 pole magnets interact
and make dot movement complex.