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Current
t h r o u g h
the reel motor flows t h r o u g h
R
22
,
a
0.1
-
ohm
r e s i s t o r t o g r o u n d
.
T h e
v o l t a g e d e v e l o p e d
across this
resistor
is
a m p l i f i e d b y IC 3
(
3 / 4
) which
i s
a
differential
amplifier
s t a g e
with
a
g a i n
factor of 10
.
The motor current
m a y
be monitored at test p o i n t 1 with a transfer function of
o n e
volt
p e r a m p
.
T h e
o u t p u t
of IC 3 (
3 / 4
)
i s
,
i n
t u r n
,
fed
back t o IC 3 ( 4 / 4 )
.
This closes the feed back
l o o p
and
p r o v i d e s a
stable transfer function
.
The t r a n s
-
conductance amplifier for the
r i g h t
reel motor
o p e r a t e s
in
e x a c t l y
the
s a m e manner
,
however
,
note that the
left and
r i g h t
reel motor connectors a r e wired
o p p o s i t e
of
each other
.
This
w a s
done
o n
p u r p o s e
.
D u r i n g
normal
s t o p o r
p l a y
t e n s i o n conditions
,
both m o t o r draw their current from
the
-
24 volt
s u p p l y
.
This balances the load o n the
+
24 volt
s u p p l y
,
which is the
c a p s t a n
motor and the
t r a n s p o r t
solenoids
.
D u r i n g
acceleration conditions when maximum
current is r e q u i r e d
,
the two motors
will draw
their currents
from
o p p o s i t e s u p p l i e s
d e p e n d i n g o n the
direction of the
acceleration
.
This also a c t s to balance the load
o n
the
p o w e r
s u p p l y
.
T h e
RMD ON
command is
o p t i c a l l y
isolated
t h r o u g h IC 1
.
IC 1
drives Q 1 which a m p l i f i e s the signal to drive the
r e l a y
K
1
.
The
r e l a y
,
when
e n e r g i z e d
,
connects
+
15 /
-
15 volts from the
v o l t a g e
r e g u l a t o r s to the o p e r a t i o n a l
a m p s
.
T u r n i n g
the
RMD
o n
and off in this
m a n n e r p r o v i d e s a s a f e t y
feature
.
If
either of t h e
+
15 volt
o r
-
15 volt
r e g u l a t o r w e r e to
fail
,
the
o p e r a t i o n a l a m p s
would drive the motors with m a x i m u m
p o w e r
,
t h e r e b y d a m a g i n g
the
t a p e
.
However ,
if both the
+
15
and
-
15 volt
s u p p l i e s
to the
o p e r a t i o n a l a m p s a r e not
p r e s e n t
,
the
o u t p u t s t a g e s
do not
r e s p o n d
at all
.
Since the
r e l a y
coil is driven
b y
the
o u t p u t s
of the
v o l t a g e
r e g u l a t o r s
,
if either of them has failed there will be
insufficient
v o l t a g e
to
e n e r g i z e
the
r e l a y s
and
a p p l y
p o w e r
to the o p e r a t i o n a l
a m p s
.
O n l y
when both the
v o l t a g e
r e g u l a t o r s a r e f u n c t i o n i n g
will there be sufficient
v o l t a g e
t o e n e r g i z e
the
r e l a y
.
The fuses
, FI
and
F 2
,
a r e p r o v i d e d
in
case there
i s
some
failure o n the
RMD
board
.
Such
a
failure will blow the fuses
rather than d e s t r o y i n g the P C board itself
.
The diodes D
16
and D 17
p r e v e n t d a m a g e
to the circuits in case the
p o w e r
s u p p l y
i s
connected backwards
.
This condition will also blow
the fuses
.
4.5
.
9
Transport Interface Board
( TIB ) Overview
T h e
TIB
,
which is located under the
o v e r l a y p a n e l
between the
reel motors
,
p r o v i d e s m o s t
of the interface functions of the
t a p e t r a n s p o r t
.
tachometers
,
bits
.
It
p e r f o r m s s i g n a l
p r o c e s s i n g
of the
i n p u t s y i e l d i n g
3 tach s i g n a l s and 3
direction
It
p e r f o r m s
A to
D
conversion of the
t e n s i o n a n a l o g
4
-
28
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