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I
pin 1l (rcl)
l 0 y f O V
pin 4 (rcl)
BA 8
Tuning meter
B A 8
F i t t i n g a T u n i n g I n d i c a t o r
Using the circuit below, it is possible to fit a 50-0-501r,4 centre zero
m e t r e i o i n d i c a t e w h e t h e r t h e m o d u l e i s a c c u r a t e l y t u n e d o r n o t .
S e t t i n g u p i s q u i t e s i m p l e , t h e 1 0 K p r e s e t p o t . s h o u l d b e a d j u s t e d
w i t h t h e A F C o u r a n d t h e m o d u l e t u n e d o f f s t a t i o n , i . e . j u s r n o i s e o n
t h e o u t p u t . T h e m e t e r s h o u l d b e s e t t o r e a d z e r o , o r c e n t r e s c a l e .
A p a r t f r o m t h e m e t e r a n d 1 0 K p r e s e t p o t . , t h e o n l y o t h e r c o m p o n -
ents required are a22KSl resistor and a 10pF electrolytic capacitor,
which can be omitted if the resultino
'flutter'
of the meter is not
o b j e c t i o n a b l e .
B A 9
S w i t c h e d T u n i n g a n d F i n e T u n e
B y b r e a k i n g t h e c i r c u i t b e t w e e n p o i n t s D C a n d G F i t i s p o s s i b l e t o f i t
prese t potentiometers and appropiate switching
The circuit below shows the details.
Note also that a separate switch position has been used to enable
t h e e x i s t i n g v a r i a b l e c o n t r o l o n t h e m o d u l e t o b e u s e d ( p o s i t i o n 1 ) .
P o s i t i o n 2 o n t h e s w i t c h a l l o w s a f i n e t u n i n g c o n t r o l , V R 1 , t o b e
u s e d i n c o n j u n c t i o n w i t h t h e e x i s t i n g t u n i n g .
S w i t c h e d t u n i n g o r f i n e t u n e c o u l d b e a v e r y u s e f u l a d d i t i o n f o r
car radio use.
B A 1 0 C o m m o n F a u l t s
H u m : c a u g e d b y i n a d e q u a t e p o w e r s u p p l y s m o o t h i n g . F i t t h e c a p -
a c i t o r m e n t i o n e d i n 8 4 . 6 .
Motorboating: caused by poor power
r e c o m m e n d e d c a o a c i t o r .
Interference: especially when the tuner
s u p p l y s t a b i l i z a t i o n : f i t t h e
is mounted on wood short-
wave interference may occur between stations. This should vanish
when a station of good strength is tuned in. lt can be reduced
h o w e v e r b y m o u n t i n g t h e t u n e r o n a m e t a l p l a t e ( o r l i n i n g t h e f r o n t
o f t h e w o o d p a n e l w i t h m e t a l f o i l b e n e a t h a n i n s u l a t i n g l a y e r ) ,
a n d / o r b y l i n k i n g p i n 5 t o p i n 7 v i a a 1 n F c a p a c i t o r .
N o i s e . B e t w e e n s t a t i o n s y o u w i l l g e t a n o i s e l i k e f r y i n g e g g s . W h e n
o n s t a t i o n i t s h o u l d d i s a p p e a r . l f i t d o e s n o t , t h e a e r i a l i s p r o b a b l y
i n a d e q u a t e - A p o o r a e r i a l w i l l c a u s e a g r e a t i n c r e a s e i n n o i s e w h e n
stereo is being received.
AFC button throwing the station off tune. This means the set is out
o f a l i g n m e n t , p r o b a b l y b e c a u s e i t h a s b e e n s c r e w e d d o w n t o o
t i g h t l y o n t o a m e t a l s u r f a c e , o r t h e a r e a o f m e t a l i n d i c a t e d i n t h e
template has not been removed properly.
A l i g n m e n t . l t s h o u l d n o t b e n e c e s s a r y t o r e a l i g n t h e t u n e r a n d a s t h e
a d . i u s t m e n t s a r e i n t e r d e p e n d a n t w e d o n o t g i v e d e t a i l s i n t h i s m a n u a l
b u t o n l y o n r e q u e s t ( S . A . E . p l e a s e ) .
Service. Experience has shown that faults in use are rare - Most of
t h e t u n e r s r e t u r n e d t o t h e S e r v i c e D e p a r t m e n t f o r
' r e p a i r '
a r e i n f a c t
w o r k i n g p r o p e r l y a n d t h e f a u l t i s i n t h e u s e r ' s i n s t a l l a t i o n .
BB Stereo Decoder
B B 1
T e c h n i c a l D e s c r i p t i o n
T h e M u l t i p l e x i n p u t s i g n a l i s f e d i n t o p i n 3 o n t h e d e c o d e r . L 2 a n d C 6
a r e t h e f i r s t 1 9 K H z f i l t e r s , L 1 a n d C 7 a r e t h e s e c o n d . L 3 i s t h e 3 8 K H z
f i l t e r . l f t h i s i s s h o r t e d o u t d e c o d i n g d o e s n o t o c c u r a n d m o n o
receotion results.
When a stereo station is being received the decoder causes the
L E D t o i l l u m i n a t e .
D ' l i s a z e n e r d i o d e t o s t a b i l i z e t h e s u p p l y v o l t a g e .
BB 2
Decoder circuit
L 2 I
I 0 1
C 1 1
, T
T ,
1 0
I
I
1 6 V
6
1 1
1 2
l 3
1 0
l c l
3
4
)
7
1 r
VR3
BA 9
Switched and fine tune
1 5
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