JVC AV-20NX3 Service Manual page 35

PURITY ADJUSTMENT
Note: The final adjustment of CONVERGENCE must be done after the
FOCUS adjustment. (CONVERGENCE is changed by FOCUS
adjustment.)
When makes difference by FOCUS adjustment, should be
reconfirming PURITY adjustment.
1. Demagnetize CRT with the demagnetizer.
2. Loosen the retainer screw of the deflection yoke.
3. Remove the wedges.
4. Input a green raster signal from the signal generator, and turn the
screen to green raster.
5. Move the deflection yoke backward.
6. Bring the long lug of the purity magnets on the short lug and position
them horizontally. (Fig. 2)
7. Adjust the gap between two lugs so that the GREEN RASTER will
come into the centre of the screen. (Fig. 3)
8. Move the deflection yoke forward, and fix the position of the deflec-
tion yoke so that the whole screen will become green.
9. Insert the wedge to the top side of the deflection yoke so that it will
not move.
10. Input a crosshatch signal.
11. Verify that the screen is horizontal.
12. Input red and blue raster signals, and make sure that purity is prop-
erly adjusted.
CRT
• P/C MAGNETS
P : PURITY MAGNET
4 : 4 POLES (convergence magnets)
6 : 6 POLES (convergence magnets)
Long lug
Short lug
(FRONT VIEW)
No. 52079
WEDGE
DEFLECTION
YOKE
P
4 6
P / C
MAGNETS
Fig. 1
PURITY MAGNETS
Bring the long lug over the short lug
and position them horizontally.
Fig. 2
GREEN RASTER
CENTRE
Fig. 3
AV-20NX3
35