ESI VideoBridge 2150, Service Manual

Page: 197 / 332

T h e v o l t a g e - t o- c ur r e n t c onver te r , U 2 , t r a n s f o r ms t h e saw t o o t h v o l t a g e
wa ve f orm a t i t s i n pu t r e s i s t o r , R l 9 , t o a saw t o o t h cu r r e n t a t i t s
o u tpu t t o d r i ve t h e ve r t i ca l y ok e .
R e s i s t o r R l 6 p r o v i d e s v e r t i ca l
h e i g h t a d j u s t m e n t o f t h e p i c t u r e o n t h e C R T b y c o n t r o l l i n g t h e
a m p l i t u d e o f t h e s a w t o o t h w a v e f o r m f r o m t h e s a w t o o t h g e n e r a t o r .
R e s i s t o r R l 7 i s a D C o f f s e t a d j u s t m e n t f o r U 2 w h i c h a l l o w s f o r
a d j u s t i n g t h e ve r t i c a l ce n t e r i n g o f t he p i c t u re on t he CRT .
Amp l i f i e r U 3 i s a b u f fe r be tw e e n t h e common bu s a n d s e n s e r e s i s t o r
R 2 2 .
R e s i s t or R 2 2 s e n s e s t h e c u r re n t f r om t h e vo l ta g e- t o- c u r r e n t
conve r t e r U 2 . T h e r e s u l t a n t v o l t a g e d rop a c r o s s R 2 2 i s s umme d w i t h
t he ou t pu t f r om U l a n d f e d ba c k t o t he i np u t t o U 2 . T h e a c t i on o f t h e
R 2 2 s e n s e f e e d b a c k i s r e f e r e n c e d a g a i n s t a s t a b l e c o m m o n b u s t o
ma i n t a i n l i nea r i t y t h ro u g hou t t he v e r t i c a l swe e p .
Res i s t o r R 20 a n d
capa c i to r C 6 pre v e n t ampl i f i e r U 2 f r om o s c i l l a t i ng w h i l e d r i v i ng t he
v e r t i ca l y ok e .
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