Kenwood DP-1100 B Service Manual page 41

1-5-6 F G & D I S C M O T O R D R I V E A N D S T O P O P E R A T I O N S
1. T h e f r e q u e n c y g e n e r a t o r consists of a polarized m a g n e t i c
ring a t t a c h e d t o the r o t a t i n g spindle of the disc m o t o r a n d
a p r i n t e d pattern in t h e f o r m of c o i l , w h i c h is p r o v i d e d at a
relative position b e l o w t h e m o t o r spindle. W h e n the m o t o r
revolves, a 2 0 Hz pulsive c u r r e n t w i t h is sent o u t per e a c h
r e v o l u t i o n of t h e m o t o r .
2 . It is f e d t o pin 7 of Q 1 0 1 a n d a sine w a v e signal w i t h an
a m p l i t u d e of ± 5 V is available at pin 8 . It is c o n v e r t e d into
a pulse signal by Q 1 0 8 a n d Q 1 0 9 , d i v i d e d t o a T T L level
by R 2 3 7 a n d R 2 3 8 a n d t h e n a p p l i e d t o pin 3 9 of IC15
( T C 1 5 G or T 7 0 0 1 ) as FGS. T h e FGS is 6 t i m e s m u l t i p l i e d
in IC15 ( T C 1 5 G or T 7 0 0 1 ) t o be DOCK o u t p u t a n d 1/30
divided t o give FG4 at pin 3 6 . Since the FGS i n c l u d e s 2 0
pulses per o n e disc m o t o r r e v o l u t i o n , the DOCK c o n t a i n s
1 2 0 pulses per a r e v o l u t i o n a n d the FG4 i n c l u d e s
pulses.
T h e DOCK is used t o d e t e c t a d r o p o u t position (Refer to
section 1 - 5 - 1 5 ) . T h e FG4 is c o u p l e d t o pin 1 4 of IC8
( T C 9 1 7 8 F ) of d e t e c t the revolution of the disc m o t o r .
D P - 1 1 0 0 B II D P - 1 1 0 0 B II
1. CIRCUIT DESCRIPTION
3 . The revolution c o n t r o l of the disc m o t o r is a c c o m p l i s h e d
by APCO ( f r o m pin 19) a n d AFCO ( f r o m pin 2 0 ) . Both of
the signals are P W M ( p u l s e - w i d t h m o d u l a t i o n ) signals w i t h
a carrier f r e q u e n c y of 8 . 2 7 kHz in the CLV m o d e . W h e n a
disc is revolving at a n o r m a l s p e e d , b o t h of the AFCO a n d
APCO are c l o c k w a v e f o r m signals w i t h a f r e q u e n c y of
8 . 2 7 kHz at a 5 0 % d u t y . Since the A F C O regulates a
range of zero r e v o l u t i o n t o h i g h r e v o l u t i o n of the disc
m o t o r , it m a y be fixed at " H " or " L " level in s o m e in­
s t a n c e s .
4 . T h e APCO a n d the AFCO are i n t e g r a t e d by R 8 5 a n d C 3 3 ,
a n d R 8 6 a n d C 3 2 respectively. T h e y are t h e n a d d e d via
R 8 7 a n d R 8 8 . T h e a d d e d signal is p u t t o pin 7 of IC4
( 1 / 2 ) . T h e o u t p u t signal g o e s t h r o u g h a l o w - p a s s filter to
4 regulate the disc m o t o r r e v o l u t i o n . C 3 5 a n d R 3 5 are for
phase c o m p e n s a t i o n . L 2 0 4 is a noise filter.
Fig. 1 - 5 - 6
5. Q 1 7 is in an OFF state d u r i n g n o r m a l play. It is ON w h e n
the disc m o t o r is n o t r u n n i n g , p r o v i d i n g 0 V o u t p u t f r o m
IC4 ( 1 / 2 ) . T h i s O N / O F F o p e r a t i o n is a c h i e v e d by MSP a n d
FGS. MSP is an o u t p u t signal m a d e available at pin 15 of
IC15 ( T C 1 5 G of T 7 0 0 1 ) by the m i c r o p r o c e s s o r . W h e n it
is at " H " level, Q 1 7 is t u r n e d OFF a n d the disc m o t o r is
driven t o r u n .
6 . Since t h e FGS p r o v i d e s 2 0 pulses per o n e revolution of the
disc m o t o r as explained previously, it m a k e s pin 7 of IC16
" H " level t h r o u g h D 4 0 d u r i n g the r e v o l u t i o n of the m o t o r
a n d Q 1 7 is t u r n e d OFF. If disc stops revolution a n d the
FGS b e c o m e s " L " , Q 1 7 t u r n s ON t o stop the disc m o t o r .
T h u s an a c c i d e n t a l rotation of the disc by noises or distur­
b a n c e s is p r e v e n t e d .