Teac MV1421, Service Manual

Page: 46 / 130

44
7-10. Base band delay line TDA4665
T D A 4 6 6 5 is a n in te g ra te d d o u b le b a s e b a n d d e la y lin e o f 6 4 .
It c o u p le s to th e T D A 8 3 7 4 a n d T D A 8 3 9 5 w ith o ut a n y s w itc h e s o r a lig n m en ts.
T h e T D A 4 6 6 5 c o n sis t o f tw o m a in b lo c k s :
- Tw o de lay lin e s o f 6 4 in sw itch e d ca p a c ito r te c hn iqu e
- In te rn a l c lo c k g e n e ra tio n o f 3 M H z , lin e lo c k e d to th e sa n d c a stle p u ls e .
T h e T D A 4 6 6 5 o p e ra te s a c co rd in g to th e m o de d e m a n d e d b y th e c o lo u r tra n sm is sio n sta n d a rd :
- F o r PA L it o p e ra te s a s g e o m e tric a d d er to sa tisfy th e PA L d e m o d u la tio n re q u irem e n ts
- In N T S C m o d e it re d u c e s c ro s s co lo ur in te rfe re n ce (co m b-filte rin g ).
- F o r S E C A M it re p ea ts th e co lo u r diffe ren c e s ig n a l o n c on s e c u tiv e h o riz on ta l s c a n lin e s .
A s a nd c a s tle p ulse is co n n e c te d to p in 5 .
T h e to p p u ls e v o ltag e (sh o u ld n o t e x ce e d 5 V ) c a n b e d ire c tly co u p le d to th e 5 V s a n d ca s tle o u tp u t o f th e
T D A 8 3 7 4 . T h e R -Y a n d B -Y co lo u r d iffe re n c e s ig n a ls (fro m T D A 8 3 7 4 p ins 30 a n d 2 9 ) a re A C -c o u p le d
a n d c la m p e d b y th e inp u t s ta g e s a t p in s 1 6 an d 1 4 .
A n in te rn a l 6 M H z cu rre n t co n tro lle d o sc illa to r is line lo c ke d via a P L L to th e sa n d c a stle p u ls e a t p in 11
a n d 1 2 . T h is c lo c k d rive s th e d e la y lin e s to o b ta in the re qu ire d 6 4ß ¡.
S a m p le a n d ho ld lo w p a s s filte rs su p re s s th e c lo c k s ig n al.
T h e orig in a l a n d th e d e la y ed sig n als a re a d d ed , b u ffe re d a n d fe d to th e o u tpu t p in s 11 a n d 1 2 .
T h e s e a re A C -c o u p le d to th e R -Y a n d B -Y co lo u r d iffe re n c e in p u t p in s 3 2 a n d 3 1 o f T D A 8 37 4 .
T h e T D A 4 6 6 5 n e e d s a 5 V su p p ly vo lta g e o n p in 1 fo r th e d ig ita l p a rt a n d on p in 9 fo r th e a n a lo g u e p a rt.
7-11. TDA8356 Vertical deflection.
T h e T D A 8 3 5 6 is a ve rtica l d e fle c tion c irc u it.
It c a n b e u se d in 9 0 ° C d e fle ctio n s y ste m s w ith fra m e fre q u e n cie s from 5 0 u p to 1 2 0 H z .
W ith its b rid g e co n fig u ra tio n th e d e fle ctio n o u tp u t c a n b e D C c o up le d w ith fe w e x te rn a l co m p o n e n ts.
O n ly a su p p ly v o lta g e fo r th e s ca n a n d a s e c on d su p p ly fo r the fly b a c k a re n e e de d .
T h e T D A 8 3 5 6 c a n d riv e m a x . 2 A .
T h e ve rtic a l d riv e c u rre n ts o f T D A 8 3 7 4 p in s 47 a n d 4 6 a re co n n e cte d to in p u t p in s 1 , 2 o f th e T D A 83 5 6 .
T h e cu rren ts a re c o nv e rte d in to a v olta g e b y a res is to r b e tw ee n p in s 1 a n d 2 .
P in 2 is o n a fix e d D C le v e l (in tern a l b ia s vo lta g e ) a n d o n p in 1 th e d riv e v o lta g e ca n b e m e a s u re d
(ty p ic al 1 .8 V p -p).
T h e driv e v o ltag e is a m p lifie d by 'A ' a n d fe d to tw o a m p lifie rs 'B ' an d 'C ', o n e is in v ertin g a n d th e o th er is
a n o n in ve rtin g a m p lifie r.
T h e ou tp u ts (pin s 4 a n d 7 ) a re c o n n e cte d to th e s erie s c o n n e ctio n o f th e v e rtic al d e flec tio n c o il a n d
fe e d b a c k res is to r. T h e v o lta g e a cro ss fe e d b a ck re s isto r is fe d v ia p in 9 to co rre ctio n a m p lifie r'D ',to o b ta in .
a d e fle ctio n c u rre n t w h ic h is p ro p o rtio n a l to th e d riv e v o lta g e .
T h e su p p ly v o lta g e fo r th e T D A 8 3 5 6 is 1 6 V a t p in 3 .
T h e fly b a ck g e n e ra to r h a s a se p a ra te su p p ly v o lta g e o f 4 5V o n p in 6 .
T h e gu a rd p u ls e is u se fu l to s yn c h ron ize O S D .