Control Of The Playback Curves; Control Of The Total Frequency Response; Power Output Control; Speed Test - TANDBERG 12 Service Manual

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5.7.16 Control of the playback curves
I n s e r t a
. l 0 0
o h m s r e s i s t o r i n s e r i e s w i t h l h e u p p e r
r e c o r d / p l a y b a c k h e a d ( c h . l ) a n d t h e l o w e r r e c o r d /
p l a y b a c k h e a d ( c h . 2 ) t o g r o u n d ( b l a c k w i r e ) . C o n n e c t
t h e a u d i o g e n e r a t o r i n s e r i e s w i t h a
. | 0 0
k o h m s
r e s i s t o r a c r o s s t h e
. l 0 0
o h m s r e s i s t o r r e f . f i g . 5 5 .
C o n n e c t t h e V T V M a n d a o s c i l l o s c o p e t o P R E . A M P
o u t p u f s c h . I a n d c h . 2 . M o v e t h e f u n c t i o n s e l e c t o r
switches to PLAYBACK position (stereo playback).
Set the speaker selector switch to position EXT.
U s e 4 0 0 c / s a s 0 d B r e f e r e n c e l e v e l .
C h e c k t h e f r e q u e n c y r e s p o n s e i n a l l t h r e e s p e e d s
a c c o r d i n g t o f i g . 4 5 .
N o f e : M a k e s u r e t h a t t h e s i g n a l i s n o t b e i n g c l i p p e d
b y o v e r l o a d i n g t h e i n p u t . T h e t o l e r a n c e s h o u l d
b e l e s s t h a n + 2 . 5 d B a t a l l f r e q u e n c i e s . T h e
d i f f e r e n c e b e t w e e n t h e t w o c h a n n e l s s h o u l d
b e l e s s t h a n 3 d B .
h E U . /
P L A Y D . -
H E A D
A U D I O -
, G E N E R A T O R
F i s . 5 5
5.7.17 Control of the toial frequency response
S e t b o t h f u n c t i o n s e l e c t o r s w i t c h e s t o R E C . p o s i t i o n
(stereo recording) and switch the FM Mz-filter off.
I n s e r t a g o o d q u a l i t y t a p e . T h e a u d i o g e n e r a t o r i s
c o n n e c t e d t o b o t h l i n e i n p u t s a n d t u n e d t o 4 0 0 c / s .
T u r n d o w n t h e o u t p u t l e v e l f r o m t h e g e n e r a t o r 2 0 d B
below max. recording level and record the frequency
s p e c t r u m f r o m 4 0 - . l 6 0 0 0 c / s a t 7 1 / z i . p . s . t a p e s p e e d .
R e w i n d t h e t a p e a n d p l a y i t b a c k w i t h a V T V M c o n -
nected to both preamp output terminals with the
speaker swiich in position EXT. and both function
s e l e c t o r s w i t c h e s i n p o s i t i o n P L A Y B A C K . C h e c k t h e
f r e q u e n c y r e s p o n s e f o r a l l s p e e d s a c c o r d i n g t o t h e
s p e c i f i c a t i o n s .
3 0 - 2 0 0 0 0 c / s ( t 2 d B 4 0 - 1 6 0 0 0 c / s )
3 0 - 1 3 0 0 0 c / s ( + 2 d B 5 0 - i 0 0 0 0 c / s )
3 0 - 7 0 0 0 c / s ( + 2 d B 6 0 - 5 0 0 0 c / s )
T h e d i f f e r e n c e i n l e v e l b e t w e e n t h e t w o c h a n n e l s
s h o u l d b e l e s s t h a n 4 d B a t a n y f r e q u e n c y .
I n c r e a s e t h e b i a s s l i g h t l y i f t h e t r e b l e i s t o o h i g h b y
a d i u s t i n g C l 0 ( c h . 1 ) a n d C l I ( c h . 2 ) . D e c r e a s e l h e
b i a s s l i g h t l y i f t h e t r e b l e r e s p o n s e i s t o o l o w b y a d -
i u s t i n g C l 0 ( c h . l ) a n d C l I ( c h . 2 ) .
Nofe:
R e c h e c k t h e d i s t o r i i o n a c c o r d i n g t o p a r a . 5 . 7 . 1 i f t h e
b i a s h a s b e e n r e d u c e d .
5.7.18 Power oulput conlrol
Connect the test equipment to the lape recorder as
d e s c r i b e d u n d e r p a r a 5 . 7 . 1 7 e x c e p t f o r t h e V T V M
w h i c h s h o u l d b e c o n n e c t e d a c r o s s a 4 o h m s , l 5 w a t t s
resifor connecfed to the external speaker output (ch. I
a n d c h . 2 ) w i t h t h e s p e a k e r s e l e c t o r i n E X T . p o s i t i o n .
Set the bass and treble controls to zero.
T h e p l a y b a c k l e v e l i s s e t b y t h e c o l u m e c o n t r o l s o
t h a t t h e V T V M r e a d s I v o i t w h e n p l a y i n g b a c k a
4 O O c l s s i g n a l . S p e c i f i c a t i o n s a s u n d e r p a r a . 5 . 7 . 1 7 .
5.7.19 Speed fest
I n s e r t a 1 4 4 c m ( 4 5 O " ) m a r k e d t a p e s e c t i o n , a n d r u n
i t t h r o u g h t h e t a p e r e c o r d e r w i t h t h e o p e r a t i n g l e v e r
i n n o r m a l f o r w a r d d r i v e . T h e t i m e f o r t h e t a o e s e c t i o n
t o p a s s b y t h e r e c o r d h e a d s h o u l d b e '
7 t / z i . p . s : 1 m i n .
3 3 / . + i . o . s . : 2 m i n .
l ' / e i . p . s . ' 4 m i n .
T h e s p e e d t o l e r a n c e s h o u l d b e + 2 % a t a l l s p e e d s .
fr
T O P L A Y B . P R E A [ " 4 P