Kenwood DP-1100 B Service Manual page 46

DP-I I O DB/ n D P - 1 1 0 0 B II
1. CIRCUIT DESCRIPTION
1 - 5 - 1 1 . P U D R I V E O P E R A T I O N
Fig. 1-5-11
Since c o n t r o l of t h e p i c k u p f e e d m o t o r s h o u l d g r a d u a l l y be
m a d e j u s t t o c o m p e n s a t e an offset of t h e t r a c k i n g error signal
d u r i n g a n o r m a l PLAY m o d e , it is d o n e by TCO + ( t r a c k i n g
coil + ) signal o n l y . D u r i n g a n o r m a l PLAY m o d e , the
TCO + s i g n a l is a p p l i e d t o pin 7 of IC3 ( 2 / 2 ) t h r o u g h R 7 4 .
Since PLAY is - 1 2 V ( p u l l e d - d o w n o u t p u t of IC16) d u r i n g
n o r m a l PLAY m o d e , Q 1 4 is OFF. In this state, IC3 ( 2 / 2 ) a n d
RC c o m p o n e n t s f o r m a l o w - p a s s filter. A s a result, the h i g h
f r e q u e n c y c o m p o n e n t s are e l i m i n a t e d f r o m T C O + signal t o
o b t a i n offset s i g n a l . It is a p p l i e d t o pin 3 of IC4 ( 2 / 2 ) t h r o u g h
R 7 8 . A f t e r g a i n a d j u s t e d , it drives t h e p i c k u p carry m o t o r
t h r o u g h R 8 0 a n d L 3 .