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o Timer Standby Circuit
T h e t i m e r s t a n d b y c i r c u i t i s c o n f i g u r e d w i t h i n l C P D 1 0 0 4 .
The TM signal is transmitted from pin 33 and is passed
through the timer standby switch and connected to the
P L A Y / R E C e n t r y i n p u t o f P D 1 0 0 4 . T h e c o n v e n t i o n a l
d i f f e r e n t i a l p u l s e ( C R ) r e q u i r e m e n t i s e l i m i n a t e d , s o t h e
c u r c u i t c o n s i s t s o f o n l y w i r i n g a n d t h e s w i t c h .
1. When the timer standby switch is set for REC or PLAY,
t h e T M o u t p u t i s p u l l e d l o w d u r i n g t h e i n i t i a l r e s e t
o c c u r r i n g i m m e d i a t e l y a f t e r p o w e r i s t u r n e d O N . a n d
t h i s c a u s e s t h e k e y i n p u t f r o m R E C o r P L A Y t o a l s o b e
l o w . ( T M o u t p u t i s n - c h a n n e l o p e n d r a i n . ) W h e n t h e
reset status is released, PD1004 goes through a POWER
O N S T O P o p e r a t i o n , a n d a f t e r t h a t o p e r a t i o n i s c o m -
pleted, the REC or PLAY entry is accepted and the
respective mode set. Switch 52 (slider switch) comes on
t o d e t e c t t h e s w i t c h i n g o p e r a t i o n s i n t o t h e R E C o r P L A Y
. SOL (Solenoid) Output Circuit
The cassette mechanism mode switching operations are
a c c o m p l i s h e d u s i n g t h e m o t o r a s a d r i v e s o u r c e . T h i s s u b -
jects the motor to quite a heavy load during these opera-
t i o n s .
C o n s e q u e n t l y , i f b a t t e r y c o n d i t i o n s h a v e d r o p p e d
t h e s o u r c e v o l t a g e t o a l e v e l t h a t w i l l b a r e l y s u s t a i n m o t o r
o p e r a t i o n s a n d s o l e n o i d o p e r a t i o n w e r e s i m u l t a n e o u s l y
a d d e d t o t h a t l o a d , t h e m o t o r w o u l d l i k e l y s t o p d u r i n g
m o d e s w i t c h i n g o p e r a t i o n s . T o p r e v e n t t h i s f r o m h a p p e n -
i n g , v o l t a g e l i m i t a t i o n s a r e p l a c e d o n s o l e n o i d o p e r a t i o n s .
T h e S O L o u t p u t c i r c u i t p r e v e n t s t h e s o l e n o i d s f r o m o p e r a -
ting when the power source voltage has dropped below the
value required for motor operation. A basic description of
t h e c i r c u i t i s p r e s e n t e d h e r e . ( R e f e r t o F i g . 2 0 )
Normally the capacitor C is charged through R to the
s a m e p o t e n t i a l t h a t e x i s t s a t p o i n t A . W h e n t h e s o l e n o i d
d r i v e r c o m e s O N , c u r r e n t f l o w s t h r o u g h R t o t h e s o l e n o i d .
but since the resistance restricts the flow of current to a
l e v e l i n s u f f i c i e n t f o r s o l e n o i d o p e r a t i o n , i t m u s t b e s u p p l e -
m e n t e d b y d i s c h a r g e c u r r e n t f r o m C .
W h e n t h e p o t e n t i a l a t p o i n t A d r o p s t o t h e l o w e r l i m i t
m o d e , a n d t h i s c u t s o f f t h e n - c h a n n e l T R ( T M o u t p u t
p i n ) w i t h t h e r e s u l t i n g o p e n s t a t u s a l l o w i n g t h e R E C
(PLAY) input to go from low to high. This opera-
tion occurs once at power ON.
2 . W h e n t h e t i m e r s t a n d y s w i t c h i s O F F a t t h e t i m e p o w e r
i s t u r n e d O N , n e i t h e r R E C o r P L A Y i n p u t s a r e p r e s e n t
a t t h e p o i n t i n i t i a l r e s e t i s c o m p l e t e d , s o t h e T M o u t p u t
p i n i m m e d i a t e l y g o e s f r o m l o w t o o p e n a n d w i l l n o t g o
l o w a g a i n . I n t h i s c a s e , o n l y t h e P O W E R O N S T O P
operation will be performed.
3 . T i m e r s t a n d b y a t E J E C T . . . . . W h e n t h e t i m e r s t a n d b y
switch is set to REC or PLAY and the cassette is ejected,
t h e E J E C T s w i t c h c u t s 0 2 ( c o n t r o l u n i t ) O F F a n d t h i s
breaks the path between the timer standby switch and
TM output. Thus, timer operation is stopped as described
i n 2 . a b o v e .
+ B +
t 2 v
S O L E N O I D
G N O
F i s . 2 O
f o r m o t o r o p e r a t i o n s , t h e v o l t a g e s u p p l i e d t o t h e s o l e n o i d
i s i n s u f f i c i e n t f o r o p e r a t i o n , a n d b y u s i n g t h e p r o p e r
resistance value for R, can be stopped there without inter-
fering with motor operation.
I n t h e a c t u a l c i r c u i t , t h e S T O P s o l e n o i d i s d e s i g n e d t o
operate at a lower voltage, so it is not connected to this
c i r c u i t . A l s o , s i n c e t h e R E C s o l e n o i d a n d P A U S E s o l e n o i d
c a n c o m e O N a t t h e s a m e t i m e ( R E C P A U S E ) , t h e v t o o u s e
a seoarate circuit.
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