Kenwood DP-1100 B Service Manual page 43

1-5-8 T R A C K I N G S E R V O O P E R A T I O N
1 . T h e o u t p u t s A A , A a n d A of 4-division p h o t o d e t e c t o r
1 ( 2 3 4
are a p p l i e d t o pin 4 t o 7 of Q 1 0 3 respectively. T h e resul­
t a n t o u t p u t ( A + A ) a p p e a r s at pin 12 a n d o u t p u t ( A
2 4 x
at pin 1 3 . T h e ( A + A ) a n d ( A + A ) are an a d d i t i o n of
1 3 2 4
p h o t o d i o d e o u t p u t in c r o s s e d p o s i t i o n , a n d are called S j
a n d S respectively. T h e S a n d S are sent t o RF a m p c o n ­
2 t 2
sisting of C-MOS inverters t r a n s f o r m e d into T T L levels.
R 2 3 9 , 2 4 7 , D 4 4 , D 4 5 , D 4 6 , a n d C 8 7 are used as level
limiter.
2 . T S i a n d T S signals ( T T L level c o n v e r t e d S S signals) are
2 v 2
c o n v e r t e d t o TEOP (pin 4 ) a n d TEON (pin 3) by the phase
c o m p a r i s o n c i r c u i t of IC15 (TC5G or T 7 0 0 1 ) . W h e n the
phase of T S is leading t h a t of T S , TEOP o u t p u t s " H "
X 2
level a n d T E O N o u t p u t s " L " level w h e n the phase of T S
lagging b e h i n d t h a t of T S .
2
3 . TEOP p r o d u c e s a f e w fine pulses at the a l m o s t " L " level
u n d e r the n o r m a l play c o n d i t i o n . On the c o n t r a r y , TEON is
a l m o s t at " H " level, p r o d u c i n g similar fine pulses. T h e
distances b e t w e e n these fine pulses s h o r t e n s , w h e n the
t r a c k i n g servo is off s u c h as in search p e r i o d .
4 6
DP-1100B II DP-1100B/H
1. CIRCUIT DESCRIPTION
4 . TEOP a n d T E O N are a d d e d via R 1 6 7 a n d R 1 6 6 a n d in­
t e g r a t e d in IC12 ( 1 / 2 ) . T h e o u t p u t is used as a TE (track­
+ A ) ing error) signal. This o u t p u t is pulled u p by R 1 6 5 t o shift
3
its q u i e s c e n t p o i n t t o 0 V , so t h a t o n l y an A C c o m p o n e n t
a p p e a r s .
5. The TE signal o u t p u t t o pin 8 of IC14 ( 1 / 2 ) is level a d ­
j u s t e d a n d applied t o pin 6 of IC1 ( 2 / 2 ) . T h e level adjust­
m e n t here c o r r e s p o n d s t o the t r a c k i n g loop gain adjust­
m e n t . T h e o u t p u t f r o m pin 8 of IC1 ( 2 / 2 ) is fed t o pin 6 of
IC2 ( 2 / 2 ) via a phase c o m p e n s a t i o n c i r c u i t , w h i c h c o m ­
pensates c h a n g e s of sensitivity c h a r a c t e r i s t i c a n d f r e q u e n ­
cy response of the t r a c k i n g coil t o insure the a p p r o p r i a t e
m o v e m e n t of the p i c k u p lens in a c c o r d a n c e w i t h a TE
is signal.
X
6 . T r a c k i n g j u m p m a y o c c u r b e c a u s e of
a m p l i t u d e of TE signal c a u s e d by s c r a t c h e s or dusts o n a
disc. RF signals are d r o p p e d o u t f o r m o r e t h a n a predeter­
m i n e d period for s u c h a c a u s e as this, the DOC signal
b e c o m e s " H " level t o m a k e D 8 , a n d Q 9 t u r n O N . This
reduces the gain of Q 8 a n d c h a n g e s the degree of the
phase c o m p e n s a t i o n in Q 9 .
F i g . 1 - 5 - 8
7. T h e o u t p u t available at pin 8 of I C 2 ( 2 / 2 ) is applied t o a
v o l t a g e limiter (limit voltage of a b o u t ± 5 V) c o n s i s t i n g of
D 9 a n d D 8 a n d sent t o the driver stage in a push-pull
cuit c o n s i s t i n g of Q 1 0 a n d Q 1 1 . T h e plus v o l t a g e is driven
an excessive by Q 1 0 a n d t h e m i n u s v o l t a g e by Q 1 1 in order t o regulate
the t r a c k i n g coil of the p i c k u p .
cir­