JVC AV-48P777/H Service Manual page 34

4.7.2 FOCUS & BEAM SPOT ADJUSTMENT
Measuring
Item
instrument
FOCUS & Similar
BEAM SPOT adhesive
adjustment (Securing
adhesive)
Remote
control unit
LENS FOCUS
SCREW
PROJECTION UNIT & LENS ASS'Y
(CRT adjustment location)
BEAM SPOT adjustment point
round as circle
4 pole magnet adjustment
CRT FOCUS adjustment point
1-34 (No.YA455)
Test point Adjustment part
Conver Service
[3. Conver Off]
R Def. yoke (DY)
G Def. yoke (DY)
B Def. yoke (DY)
[PROJECTION UNIT]
R LENS FOCUS screw
G LENS FOCUS screw
B LENS FOCUS screw
[PROJECTION UNIT
(LENS ASS'Y)]
4 pole magnet
2 pole magnet
[PROJECTION UNIT
(R / G / B CRT neck)]
R FOCUS VR
G FOCUS VR
B FOCUS VR
[FOCUS PACK]
DEFLECTION CENTERING
YOKE MAGNET
4 POLE 2 POLE
MAGNET MAGNET
< Defocus > < Optimum Focus >
optimum center and defocus
center should be same point
2 pole magnet adjustment
red
blue blue
green
Description
(1) Select FULL mode with [ASPECT] key.
(2) Select DYNAMIC mode with [VIDEO STATUS] key.
(3) Select 3. Conver Off from Conver Service menu,
then dot pattern is appear.
(4) Press [INPUT] key to appear crosshatch pattern.
(5) Adjust the R, G and B DY position to mark straight
horizontal line.
LENS FOCUS
(1) Make a red single color.
NOTE :
When making a single color, while adjusting focus of
one CRT, put the cap on other lens.
(2) Turn the R LENS FOCUS screw (in LENS ASS'Y),
for optimum focus at the screen center. Check for
absence of difference in the peripheral focus. If the
peripheral focus is poor, slightly shift the center
focus to obtain overall balanced focus.
(3) In the same manner, produce green and blue single
color and adjust their respective focus.
(4) Fix the LENS FOCUS screws.
NOTE :
There is not a difference in the focus in the top and the
bottom, on either side, in the diagonal.
When the difference of the focus is big, remove a
main lens and put a washer between the main lens
and the coupler, and then re-adjust it.
BEAM SPOT
(5) Change dot pattern with [INPUT] key.
(6) Make a red single color.
(7) Turn the R FOCUS VR clockwise from just focus
point, to set the dot diameter to approx. 30mm.
(8) Turn the 4 pole magnet of the projection unit CRT
neck and make beam shape round as circle on the
position between center and both ends of the
screen.
(9) Adjust the R FOCUS VR for optimum focus at the
position indicated in the figure.
(10) Turn the 2 pole magnet of the CRT neck as optimum
focus and defocus center should become the same
point.
(11) In the same manner, adjust for the green and blue
single color focus.
(12) Secure the 4 and 2 pole magnets with similar
adhesive.
CRT FOCUS
(13) Change crosshatch pattern with [INPUT] key.
(14) Select DYNAMIC mode with [VIDEO STATUS] key.
(15) Make a red single color.
(16) Adjust the R FOCUS VR for optimum focus at the
position indicated in the figure.
(17) In the same manner, adjust for the green and blue
single color focus.