JVC AV-20D304/SA Service Manual page 24

3.6.8 PURITY AND CONVERGENCE
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 center of the screen. (Fig.3)
(8) Move the deflection yoke forward, and fix the position of the
deflection 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 properly adjusted.
WEDGE
CRT
MAGNETS
P/C MAGNETS
P : PURITY MAGNET
4 : 4 POLES (convergence magnets)
6 : 6 POLES (convergence magnets)
Fig.1
PURITY MAGNETS
Long lug
Short lug
Bring the long lug over the short lug
and position them horizontally.
Fig.2
(FRONT VIEW)
GREEN RASTER
CENTER
Fig.3
AV-20D304
DEFLECTION
YOKE
P / C
(No.52103)1-23