JVC AV-N48P55 Service Manual page 44

4.7.3 FOCUS & BEAM SPOT ADJUSTMENT
Measuring
Item
instrument
FOCUS & Signal
BEAM SPOT generator
adjustment
Similar
adhesive
(Securing
adhesive)
LENS FOCUS
SCREW
PROJECTION UNIT & LENS ASS'Y
(CRT adjustment location)
BEAM SPOT adjustment point
< Beam shape : distortion > < Beam shape : circle >
round as circle
4 pole magnet adjustment
blue
CRT FOCUS adjustment point
1-44 (No.YA166)
Test point Adjustment part
TEST MODE
[5.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
green
Description
(1) Receive NTSC crosshatch signal.
(2) Select FULL mode with [ASPECT] key.
(3) Select DYNAMIC mode with [VIDEO STATUS] key.
(4) Select 5.CONVER OFF from TEST MODE menu,
then dot pattern is appear.
(5) Press [INPUT] key to appear crosshatch pattern.
(6) Adjust the R, G and B DY position to mark straight
horizontal line.
LENS FOCUS
(1) Makes a red single color.
NOTE:
When making a single color, while adjusting focus of
one CRT, put the cap on other lens.
(2) By turning the 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) After adjustment, fixes a screw.
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, it removes a
main lens, and it puts a washer between the main lens
and the coupler and adjusts it.
BEAM SPOT
(5) Change dot pattern with [INPUT] key.
(6) Makes a red single color.
(7) Turn the R FOCUS VR clockwise from just focus
point, to set the dot diameter approx. to Ø30mm.
(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 adhe-
sive.
CRT FOCUS
(13) Receive NTSC crosshatch signal.
(14) Select DYNAMIC mode with [VIDEO STATUS] key.
(15) Makes 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.