ESI VideoBridge 2150, Service Manual

Page: 198 / 332

3 . 5 . 4
H o r i z on ta l D r i ve
The H o r i z on t a l S y n c s i g n a l c omes i n on p i n 5 o f P 3 0 1 a nd i s f e d t o the
hor i z on tal osc i l l a t o r , U 1 4 . The s y n c h r on i z e d os c i l l a t o'r i s u sed to
prov ide d r i ve o f t h e app ropr i a t e d u ty cyc l e t o the rna i n h or i z on t a l
sw i t c h i n g t ra n s i s t o r Q7 , a VMOS pow e r F E T . T h e h o r i z on t a l o s c i l l a tor
ha s a s ta r t up d e l a y c i r c u i t c o n s i s t i ng of C 1 2 , R 2 7 , CR6 a n d CR7 to
a l l ow t h e pow e r supply t o s t a b i l i z e b e f o re d r i ve i s a pp l i e d t o Q 7 .
W h e n Q7 i s t u r n e d on , a c u r r e n t f l ow s i n t o t he p r i ma ry o f T l s to r i ng
e n e r g y a s a ma g n e t i c f i e l d i n t h e c o r e o f T l . A t t h e s a m e t i m e ,
c ha rg i ng c u r re n t i s supp l i e d t o capa c i t o r C 1 4 t o s u p p l y t h e 40VDC
req u i r e d f o r the v i de o ampl i f i e r and ve r t i ca l r e t ra ce
b l a n k i n g
c i r c u i t s . W h e n Q 7 i s t u r n e d o f f , e n e r g y i n t h e c o r e i s s u p p l i e d
t h r o ug h t h e ho r i z on ta l w i d th a n d ho r i z on ta l l i n ea r i ty c o n t r o l s ( L l ,
C 1 6 , a n d L 2 ) t o t he de f l e c t i on yoke . The ma g n e t i c f i e l d p r oduced by
the de f l e c t i on y ok e swe e p s t h e e l e c t r on b e a m a c r o s s t h e CRT f a ce .
Hor i z on t a l p o s i t i on i s p ropor t i ona l t o t h e a mo u n t a n d p o l a r i ty o f
cu r r e n t f l ow i n g t h r o u g h t h e de f l e c t i on yoke . Capa c i t o r s C 1 5 a n d C 1 6 ,
a n d l i n e a r i ty c o i l L 1 p rov i de p r ope r w a v e s h a p i n g o f t he de f l e c t i on
s i g n a l . E n e r g y s t o r e d i n t h e c o r e o f T l i s a l s o s u p p l i e d t o t h e
se c onda ry o f T l p ro v i d i n g t he v o l t a g e s ne ce s s a ry f o r c a t h o d e ray t u be
ope ra t i on .
D i ode re c t i f i e rs CR9 , CR I O , CR l l , a n d C R 1 2 d e v e l op t he DC
a c c e l e r a t i ng a n d f o c u s i n g vol t a g e s f o r the CRT . T he h i g h vol t a g e a t
the C RT ' s a n ode , f o r f i na l e l e c t ron a c c e l e ra t i on , i s 6kVDC . D i sp l a y
br i g h t n e s s a n d f oc u s a re c o n t ro l l e d by R 3 3 a n d R3 2 r e sp e c t i ve ly .
3 . 5 . 5
V i de o Control S umma ry
T h i s s e c t i on de s c r i be s t he v i deo c on t r o l s a v a i l a b l e f or a d j u s t i ng t h e
qua l i ty o f t h e C R T d i sp l a y .
The v i de o a d j u s tmen t s d e s c r i be d i n t h i s
s e c t i on a r e s e t f o r t h e b e s t p o s s i b l e d i s p l a y a t t h e f a c t ory j u s t
p r i o r t o s h i pp i n g a n d need b e repea t e d
c i r c u m s t a n c e s . ( N o t e t h e f o l l ow i ng C A UT I ON . )
3 - 3 3
e \ s \ i 2 1 5 0/ 2 1 6 0 5 / 8 5
on l y u n d e r e x t r e me