NEC JC-1531 VMA-2, Service Manual

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( 1 2 ) C u t - o f f
( a ) lnit
adjustment Signal 3 (VGA480)
ial s e t t i n g s o f t h e a d j u s t m e n t VRs
VR704-VR706 B I A S V R
:
F u l l y c o u n t e r c
VR707-VR709 SUB BRIGHT VR
:
F u l l y c o u n t e r c
SCREEN VR
:
F u l l y c o u n t e r c
VR710 SUB BIAS VR
:
F u l l y c o u n t e r c
CONTRAST CONTROL
:
F u l l y c o u n t e r c
BR
I
GHTNESS CONTROL
:
F u l l y c o u n t e r c
( b ) R e c e i v e a n a l l - b l a c k s i g n a l .
ockw i se
ockw i se
ockw i se
ockw i se
ockw i se
ockw i se
(c) Short CN-TP and (Use CN-TP- on Adjustment j ig)
Short SW45 on Adjustment j ig. (TP-B and
(d) Connect a high voltage voltmeter to TP904 and adjust the SCREEN VR
s o t h a t t h e v o l t a g e i s 4 7 0 V d c ±5Vdc(VMA-2(N),(NT),(H)/VMB-2(N),
(NT),
(H)/VMR-2(N), (H))
or 665Vdc ±5Vdc(VMA-2(T)/VMB-2(T).
(Use a voltmeter with a maximum voltage capacity of 1.5kV
o r g r e a t e r a n d a n i n p u t r e s i s t a n c e o f o r g r e a t e r . )
( e ) T u r n i n g VR-71O(SUB B I A S V R ) g r a d u a l l y i n t h e c l o c k w i s e d i r e c t i o n
w i l l c a u s e
a
s i g n a l c o l o r t o a p p e a r horizontally. Set the VR so that
t h e c o l o r c a n b e f a i n t l y s e e n . T h i s c o l o r i s t h e r e f e r e n c e c o l o r f o r
t h e c u t - o f f adjustment.Even i f t h e r e f e r e n c e c o l o r d o e s n o t a p p e a r ,
p r o c e e d t o s t e p ( f ) .
(f) Turn the BIAS VRs(on the VIDEO PWB) for the colors other than the
r e f e r e n c e c o l o r i n t h e c l o c k w i s e d i r e c t i o n u n t i l t h e c o l o r s l i g h t
w i t h s a m e b r i g h t n e s s a s t h e r e f e r e n c e color.lf even it the reference
c o l o r w i l l n o t a p p e a r V R 7 1 0 t u r n e d f u l l y c l o c k w i s e , t u r n V R 7 0 5
c l o c k w i s e u n i t i l t h e g r e e n h o r i z o n t a l d i s p l a y a p p e a r s faintly.Use
a s t h e r e f e r e n c e color.Next turn VR704 and VR706 until their
corresponding colors light with the same brightness as the
r e f e r e n c e c o l o r .
(g) Open the short SW45 on Adjustment jig. (TP-B between and
N O T E - : W h i t e t r a c k i n g w i l l b e b e s t a t d a r k c u t - o f f a d j u s t m e n t s e t t i n g s .
F o r t h e b e s t s e t t i n g , t h e r e f o r e , p e r f o r m t h e c u t - o f f a d j u s t m e n t
in as dark a place as possible.
(13) Cut-off Faint Adjustment (Contrast Tracking) signal 13 (VGA480 WINDOW)
(a) Receive the window pattern.
(b) Short SW44 o n A d j u s t m e n t j ig. (TP-B and
(c) L e a v e C N - T P
and s h o r t .
(d) T u r n t h e c o n t r a s t c o n t r o l f u l l y clockwise(MAX) a n d m e a s u r e
t h e c o l o r t e m p e r a t u r e (Xl,Yl).
( e ) T u r n t h e c o n t r a s t c o n t r o l f u l l y c o u n t e r c l o c k w i s e ( M I N ) a n d m e a s u r e t h e
c o l o r t e m p e r a t u r e (X2,Y2).Faintly adjust the BIAS VRs of the colors
o t h e r t h a n t h e c u t - o f f r e f e r e n c e c o l o r s o t h a t (Xl,Yl)=(X2,Y2).
I f t h i s a d j u s t m e n t i s d i f f i c u l t , t r y f a i n t l y a d j u s t i n g t h e
BIAS VR of the reference color.
(f) Turn the contrast control again fully clockwise(MAX) and measure
the color temperature. If the color temperature has shifted, repeat
t h e f a i n t a d j u s t m e n t p r o c e d u r e i n s t e p ( e ) .
0 0 5
0 0 5
.
(g) Remove the short between CN-TP and
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