Via
the
analog
switch
lC
9007
pin
112 and
resistor R 9030,the
partial
voltage
set with
the
pitch
potentiometer
P 33
and P 45 is additionally
applied to
pin
5
of lC
9005,
thus making
a speed alteration
oI
+
6 %
possible.
ln
quartz
mode,
the
pitch
control loop is
rendered
ineffective
by opening
lC
9007
pin
112.
Ouartz
circuit
The
quartz
circuit has
the task
of
providing
the time
reference for
driving the stroboscope
and the
phase
comparator.
By means
of the
phase
comparator,
the speed
control circuit
is influenced
in
such a
way that
a closed
phase
control
loop
(PLL)
is
produced
which
transposes
the
position
of the crystal
oscillator
on
the speed.
The
crystal
oscillator, consisting
of T
9001
,
C 9001
-3,
R
9001
,
R
9002
and the crystal
O
9001
,
drives the
programmable divider
lC
9001
at
pin
9.
lf the
speed selector is
set to
"33",
the input
data
P1 to PB
have
the bit
pattern:
L
H L L
L H L H. This
corresponds
to
thedecimal
number 162, with
the significance
of P1
-
Pg corresponding
to the
numbers 1,
2, 4, 8,
16, 32, 64
and 128. When
the selector
is set
to
"45",
thedecimal
number 120 is
represented
by the bit
pattern
(P1
-
Pg)
L L
L L L L H
H. ln this
case, due to
pin
2, the signif icance
of P1
to P8
is as follows:
1, 2,
4,
8,
10, 20,
40 and 80. The
frequencies
28.44
k{z
and
38.40
kHz
are now available
at the output
pin
15 for further fre-
quency
duration. The
f requencies 11 1
Hz and
'150
Hz are
generated by
lC
9003
with
eight stages and
these
precisely
correspond
to the control
frequencies
for
the speeds
33 and
45 rpm.
Via
the inverter
lC 9006
pin
11l10,
the
phase
comparator,
consisting
of the two D
f
lip-flops
in
lC 9004
and R 9010
and
D 9001,
is
driven with the
set frequency.
lt
receives
the actual current
speed via inverter
lC
9006
pin
1/2
from
pin
1
of IC 9005.
Viathe
phase
anglesf
rom
-360
to
+360,
the information
is
applied
in the form
of variable
puise
widths
at
outputs
pin
13
and
pin
2
of lC
9004.
These
signals are
decoupled by diodes D 9002
and D 9003
and matched with
R
901
1
and
R
9012
to the control
circuitry in such
a
way that
a synchronous
holding range
from
-5%to
+2
%
is
obtained.
Synchronization is
achieved by the fact
that a
positive
current flows
through
R
901 1 to
the speed determining
capacitor C
9015
in the event
of
a leading
phase
angle. This
reduces the
sawtooth
voltage
(measured
lrom
+
12
V), resulting
in
a decrease in the motor
currenl. lf the
phase
angle
lags,
a negative current f lows through
R
901
2
to
C
901 5,
resulting
in an increase in
the
motor
current. These decreases and increases result
in stabilization of the
preset
speed.
Start-up synchronization
lf the motor current
increases
too much
due to an increased
torque load
or
during start-up, the start-up
synchronization
is
activated
due to the
voltage drop at R 9044
via T 9007
and
lC
9006
pin
5/6,
and diode
D
9005
is
caused
to
block. The
generator
pulses
at
lC
9005
pin
i
are
differentiated by C 9007
and R
9005
after the lnverter
lC 9006
pin
1/2
and, via R
9006,
these
pulses
reach the reset input
of the
quartz
divider
whose output frequency
runs synchronously
with the
generator
frequency
as the result
of
this.
Thus, there is
no speed modifiying
signal
at theout-
put
of the
phase
comparator
and, as the
result of this, the
drive
locks
in
exactly
the nominal speed.
As the voltage
drop at R 9044
now d
isappears,
pin
6
of lC
9006
pin
5/6 becomes
low,
D 9005
becomes conductive
and
the start up
synchronization is
deactivated.
Via
the
phase
comparator,
the speed is
now kept
phase-rigid
by means
of
the
quartz
divider
which
is
now
running
freely.
Stroboscrope
The
precise
crystal-controlled
output frequency
of
divider
lC
9002
ls
differentiated
by R
9009,
C
9O0B
and R 901
3 and, via
dlode
D
9004,
routed
to the base of T 9002.
This
briefly
becomes reverse-biased
and,
at
the
base
of T 9003,
a voltage
sets in which is
generated by resistors
R
9014
and R 9015
wired
as a voltage
divider. Thls base
voltage
now
causes
T
9003
to become
conductive until
a voltage
appears at
the emit-
ter resistor
R
9016
which is
approximately
0.7
V lower than
at thebase.
As the base
voltage is
constant, the
voltage
at R
9016
is also
constant
and, as the result cif
this. the
collector current is
almost independent
of
the
load
resistance
lLED
voltäge).
The stroboscope
LED's thus
light up
with a
constant
pulse-shaped current
in
which
case their
"on"
duration
mainly
depends on
C
9008
and.f 9013.
At 33
rpm, the repetition
fre
quency
is 55.5
Hz and, at 45 rpm,
the f
requency
is
75 Hz and is
precisely
crysta I co
nt ro
I
I
ed
.
Motor bridge
output
stage and
power
supfly
The
following
circuit
is accommodated
on
a separate
printed
circuit
board. The
communtation
transistors
T 9201
to T 9204
are
alternately
driven
by the
hall
generator
in
the motor,
as the result
of
which they
are
forward-biased
to
a
greater or
lesser
extent
depending
on
thedrain-source
resistance
of T 9008.
Accordingly,
via
reislors R 9202
-
R
9205,
the
corresponding
PNP
transistors
T
9205
-
T 9208
become
conductive,
resulting in
a
brldge arrangement.
The
transistors
T 920'l
and T 9206,
T 9202
and
T
9205,
T
9203
and T 9208,
I 9204and
T 9207
arethen
switched
in
pairs.
C 9202
and
C 9203
prevent
steep
current edges
during
switchover
of
the bridge.
The
hall
generator
voltage
is
produced
by
R 9201
and the
1.1
kOhm resistors
in
the
motor' Transistors
I 9201
-
f
g2O4
are
screwed
onto a
heat
sink, also
accommodating
the
voltage
controllers
for
the control
circuitry, for
better
heat dissipation.
C
9201
and
C
9204
suppress
the inclination
of
the
controller
circuitry
to
oscl llate.
Display
The display serves to
visually
indicate the
following
conditions:
33 and
45 rpm speed
display,
quartz
or
pitch
mode and display of the
pitch
deviation
tn %.
f he
two
LED's
for
the 33
and 45
rpm
speed indi-
cation
light
up alternately depending on the switch
setting.
lf there is
an
excessive torque
load on the
platter,
and in
the start
up
phase,
the anode
potential
is connected to
ground
by T 9301,
as the
result
of which
they are
extinguished.
The two
LED's
for
quartz
or
pitch
mode also
light
up
depending
on the
switch
setting
S 2. When the switch
S 2
is set
to
,,quartz",
the
LED's of
the
pitch
display
are
blanked additionally
by D 93O7
and lC 9301-
This
is
also the
case in
the
start
up
phase
and when
the
platter
is
braked
ex
tremely.
lC
9301
.
and thus
the
LED
scale,
is
driven with
the
pitch
control.
lts
voltage range
from
0
. .12V
corresponds
to the
range of the
LED
scale
from
-6o/o
to
+6o/o.
Distributor
board
The
printed
circuit board
comprises the
rectifier
circuit
D
9451
-
D
9454,
the
RF filters C
9451
and
C
9452
and the
1O0
Hz filter consi-
sting of
C
9453.
ln addition,
the
pc
board serves as
the
central wirding
board.
The
front controls, the solenoids
and the
micro switches
are
wired
here.
Start
function
The
start
solenoid
M
1
is
energized when the start
button
S
4 is
depres-
sed.
lts self
holding
contact S 1 2
holds
the
magnet in operating
position
via
D
9456
and T
9451.
The motor
circuitry
is
switched to 0
V via
D
9455.
lf the
cam wheel then
clicks through, the drive switch
S 8 is
activated.
The motor
circuitry
is
now
completely connected to
ground.
Briefly before the
cam
wheel
moves to its
zero
position,
it
pushes
back
the
armature
of
the start
solenoid
M
1 and the solenoid
is deenergized.
lf,
at
the
beginning
of the
start
phase,
the
cam of the
motor
pinion
is in
such an
unfavorabte
position
that the
armature
of the start
solenoid
can
not completely
push
forward
the switch
off
mechanism,
and the
motor
can not be started,
as the
armature
does
not reach
holding
contact. ln
order
to
prevent
this,
the
motor circuitry receives
current
via D
946'1 in
this
case. The
motor
starts
to
turn and the
start
procedure
runs
pro-
perly.
Continuous
play
f unction
The continuous
play
button
S 3
has
a locking
function. lt
can be
un-
locked
by
pressing
it
once again or
by depressing
the stop
button
S 5.
The
continuous
play
button
connects the start
solenoid
M
1 to
the
.,continuous
play"
cam
switch
S
9 in
such
a way that the start
function
and
not
the stop
function
is
trlggered
off
after a
record has been
played.
Stop
function
For
the stop
function,
the start solenoid
M
1
must
only remain in its
operating
position
for a
short
time
(maximallv
114 of a
cam rotation).
lf it
remains
in
f
unction
for
a
longer
time, the deflection segment of the
cam thweel is
actuated.
This
then corresponds to
the
start
function.
ln order to
ensure that the self-holding
contact S
12
of the solenoid
M
1 is released, the
distributor boards contains a
circuit which briefly
keeps current
from
the solenoid
M
1 after the
stop button S
5
is re-
leased
or, at the latest,
when the cam wheel-continuous
play
switch
S
I
is switched
over.
Normally,
this interruption
circuit conducts a
current. The
base of
T
9451 is
kept
at
positlve potential
via R
9452.
lf
the stop
button
S
5
is
depressed, capacitor
C
9454
is discharged
via
R
9453.
After the
start
button is
released or after switchover of the
cam
switch
S
9,
C
9454
can
charge
up
via
R
9452.
ln
this way. transistor
T
9451
remains reverse-
biased
until
its swltching threshold
of approximately
5
V
is
reached.
During
this
period,
the armature
of the
start
solenoid
M
1
must
be de-
energized
so that the stop
function
can operate
properly.
This
time
amountes
to 0.075 s to
0-3 s.
Diode
D
9459
permits
energization of the start solenoid
M
1 when stop
is
actuated.
The diode
D
9460
prevents
C 9454
from
charging
up via
the
branch of
D
9459.
C
9454 should
charge up
via
R
9452.
D
9456
additionally increases
the
emitter
potential
to
ensure
proper
operation.
D
9455
prevents
response
of the start solenoid
when the
unit is swit-
ched on
manually.
D
9457
and
D
9458 suppress
negative
peak
voltages
at the solenoids
du-
ring switch
off .
Muting
The AF-signal
is
fed
from the cartridge
to the
muting switch
S 11,
which is
open in the
basic
position
of the
cam. The
contacts of
the
muting
relay RL 940'l
is
parallel
with
the switch
S 11. This
relay is
driven
via the
switches
S 4
-
Start,S
9
-
Continous
Play
and S6
-
Lift.
The relay is
closed for
approx.
1.2 seconds.
Descrip
Electronir
L'61
ect
ro r
tionnels
s
Electroni
r
Bloc ä
qu
Circuit
de
Etage
fini
Electronir
La
fr6que
tu
rba tr
ic€
prdamplif
le
signal
r
teur
opÖr
Sch mitt.
par
C
90
ddfini
de
impulsior
passant
p
ci6es
par
T 9005,
r
par
l'inte
C
9015
r
res i sta nc€
seules
R
analogiqr
et
R
901
"33"
et
r
scie ainsi
tension
n
de
scie e
est
g6n6n
L'i
nterru
de lC
90
continue
dente
par
L'616men
T
9006
p
T 9006 c
C9019e
a eu
lier
des d ioc
R
9038.
dur6e
de
de
C
901
soit
past
C
9020,
I
R
9036,
dömarre
ldentif icr
Du fait
r6sistanci
mat
ivemr
T
9007
r
et
R
904
rage, ce
signal ac'
ä
quartz
ä la corr
Pin
5
lC
R
9033
enclique
cette inf
cas, le
ci
Circuit
d
La tensir
du
coup
par
l'inte
d
Pin
5
r
F
9044
en
registr
commut
La tensi
P
45
es1
l'i
n
ter ru
I
qul
renc
quartz, I
Pin
1/2.
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