Panasonic Technics SL-1810

But
the
unit
is
not
affected
by
the
fluctuations
of
the
power
source,
since
a
D.C.
motor
is
employed.
If
the
desired
speed
can
not
be
obtained
by
the
variable
pitch
controls,
turn
the
speed
adjusting
screws
with
a
screw
driver
for
further
adjustments.
(See
Fig.
9)
Z
Cross
section
of
motor
portion
and
double
insulator
Motor
shaft
(Center
spindle)
Position
detecting
rotor
Stator
Position
detecting
coil
Tonearm
Turntable
mat
Stator
coil
Dust
cover
[|
poem
cn
aD
me
(eee
EP
A
Rotor
magnet
i
Turntable
platter
=
r
—
ee
p
|
Arm
base
Turntable base
‘¢
SN
Ss
Spring
.
loom
a
a
Bs
1st
insulator
soe
Nea
mi
pn,
2nd
insulator
Sceheueane
Visco-elastic
material
|
Main
base
= Operation principles of the SL-1800
This
unit,
like
the
SL
1300
has
a
rational
motor
structure,
and
its
drive
control
circuit
is
the
B.F.G.
type
(Back
TECHNICAL
EXPLANATION
electromotive
force
frequency
generator)
which
is
constructed
on
a
single
integrated
circuit
(IC)
chip
(AN630).
The
following
is
a
block
diagram
of
the
IC
(AN630)
for
which
the
operating
principle
will
be
briefly
explained.
m
Operating
principle
The
back
electromotive
force,
which
is
generated
by
the
frequency
components,
with
the
operational-amplifier
drive
coil
winding
according
to
the
rotation
of
the
active
filter,
from
this
voltage
signal,
it
controls
the
cur-
motor,
is
detected
and
converted
to
a
frequency
signal
rent
flow
in
three
differential
switching
circuits.
Asa
that
is
proportional
to
the
number
of
revolutions.
result,
the
flow
of
current
in
the
drive
coil
winding
Is
Conversion
is
performed
by
a
wave-shaping
circuit
and
a
always
constant
maintaining
the
correct
rotational
spe-
logic
circuit.
(This
is
referred
to
as
the
B.F.G.
method).
ed.
Control
of
the
rotational
speed
can
be
performed
by
This
frequency
signal
is
compared
with
a standard signal
means
of
adjusting
the standard
signal
generator
circuit
by
means
of
a
frequency-voltage
conversion
circuit
according
to
the
rotational
speed
adjustment
circuit.
which converts it to a voltage signal in order maintain a
constant number of revolutions. After removing un-
necessary
SL-1800/ SL-1800A