Adjustment Of The Osc. Frequency And The Bias; Bottom View Of The Tape Recorder; Connections - TANDBERG 12 Service Manual

F i g . 5 3 . B o t t o m v i e w o f t h e t o p e r e c o r d e r .
5.7.1| Adluslmenl of the osc. frequency
and the bias.
C o n n e c t i o n s :
Connect the VTVM and a frequency meter in parallel
to a 100 ohms resistor in series with the lower record/
p l a y b a c k h e a d t o g r o u n d ( b l u e w i r e ) . S e t b o t h f u n c -
tion selector switches to REC pos. (s'fereo recording).
A d i u s t C l 2 0 u n t i l t h e f r e q u e n c y m e t e r s h o w s 8 5 , 5
K c / s a n d a d i u s t C i i u n t i l t h e V T V M r e a d s 6 5 m V ( T h e
r e a d i n g f o r t h e f w o - t r a c k v e r s i o n s h o u l d b e 9 5 m V ) .
Connect the VTVM across the
.l00
ohms resistor now
c o n n e c t e d i n s e r i e s w i t h t h e u p p e r r e c o r d h e a d ( c h . l )
t h e g r o u n d ( r e d w i r e ) . A d i u s t C l 0 u n t i l t h e r e a d i n g
o n t h e V T V M s h o w s 6 5 m V . ( T h e r e a d i n g f o r t h e t w o -
t r a c k v e r s i o n s h o u l d b e 9 5 m V . ) C h e c k t h e f r e q u e n c y
t o b e 8 5 . 5 k c / s a n d r e a d i u s t C l 2 0 i f n e c e s s a r v . S e t
the function selector switch ch. 2 to PLAYBACK posi-
t i o n a n d a d i u s t L 3 u n t i l t h e f r e q u e n c y m e t e r r e a d s
6 5 . C K C / S .
Set the function selector switch ch. I to PLAYBACK
p o s i t i o n a n d t h e f u n c t i o n s e l e c t o r s w i t c h c h . 2 t o
R E C O R D p o s i t i o n .
Connect the VTVM and the frequency meter across
t h e
. l 0 0
o h m s r e s i s t o r c o n n e c t e d i n s e r i e s w i t h t h e
lower record head (ch. 2). Check the frequency to be
85.5 kc/s + 2 kc/s. lf the deviation is more than 2 kc/s,
L3 must be readjusted to compromise so that the
d e v i a t i o n i s e q u a l b e l w e e n c h . I a n d c h . 2 .
The bias voltage tolerance between mono and stereo
i s + l 0 % . T h e H F v o l t a g e a c r o s s t h e e r a s e h e a d s h o u l d
be 80-l l0 volts. The tolerance belween mono and
s t e r e o i s + l 0 % .
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