Dokorder 7700 - Page 29

"REC"
to auto
shut-off
"ON"
mode
v
v
Fis.
8 8
\r'
8-2 CAPSTAN MOTOR DRIVE
CIRCU
The capstan
motor is the
heart of open-reel
tape
decks. Dokorder
products
have
for
a
long
time
used large-type,
hysteresis
synchronous AC
motors that
are superior to
DC
motors in terms of
heat
emission, stability
against
load conditions
and long service
life. But
AC motors require
somewhat
large
power
consumption,
and also
have
certain
restrictions
in
the
improvement
of
their
wow-flutter
characteristics
because the
number of
poles
is
limited
in them.
Recent developments
in
the
design
and
manufacture of
DC motors,
however,
have introduced
compact
but
high-performance
DC
motors.
ln addition, supported
by the development
of servo
techniques
to drive and
\;/
control
DC
motors, low-cost,
compact
and
low-power-consumption
motors
have
become available that
combine
the
advantages
of the DC
motor
and servo
control
circuit.
This combination
ensures
sufficiently
stable
motor
speed s
and
prom
i nent wow-f
I utter
characteristics.
Dokorder
has
developed
a
unique servo
circuit,
and installed
it
and
a DC
motor together
in
the
latest
Model
7700.
The servo
control circuit
not only
enables
a
very
high
production
yield
for
this
tape
deck.
2-(A)
Schematic of C.P.M.
(Capstan
Motor) Control
Circuit
(D)
Bridge-type
Motor
Drive Circuil
(c)
PLL Control
Circuit
(A)
PUT Reference
Oscillator
F ig. 8-9
v
26