Sansui FR-D4 - Operation of Micro Computer Periphery Circuits; Protection Program; Protection for Plunger Solenoid and Motors; Emergency Stop Operation

(4)Protection Program
A. Protection of Plunger solenoid | B. Emargency Stop
& Motors(In case that tonearm (In case that tonearm is
is clamped on its rest.) on the way of returning.)
START/STOP SW
REPEAT SW
33/45r.p.m Selector
30/17cm Selector
A-SENSOR
B-SENSOR
C-SENSOR
D-SENSOR
iI
Wt
et
"W ii
=\Record End
Signal
PrCrzrPIercaraweric =
OUTPUT
CW
CCW
MICROMOTOR-{_
PLUNGER
D.D.MOTOR
REPEAT INDICATOR
2. Manual Operation
1) When tonearm is moved from arm rest, photo-transistors of A,B
sensors turn OFF, which causes input port R4, Rs of MB8844 to
be L. At this time output port O3 of MB8844 turns to H from L
that DD Motor starts rotating.
2) When pushing START/STOP switch after placing tonearm to
desired position, arm lifter is lowered since output port Ro be-
comes L from H.
3) The same function as A-4) ~ 6) in full-auto operation is per-
formed after tonearm is lowered, however, if tonearm is returned
manually during record playing, photo-transistors of A, B sen-
sors turn ON just before tonearm reaches its rest that input ports
Ry,
Rs
of
MB8844
become
H.
At
this
time,
output
port
O03
changes to L from H that rotation of DD Motor is stopped.
3. Cut Operation
The tonearm returns to its rest immediately during any operation if
START/STOP switch is pushed.
For instance, if START/STOP switch is pushed during record play-
ing, output port Ro turns to L from H simultaneously to input port
Ko to H from L that tonearm returns as the same way of A-4) ~ 6)
in full-auto operation.
4. Protection Program
Two sorts of protection programs are provided with MB8844 for
extraordinary operation of the unit.
A. Protection for Plunger Solenoid and Motors
1) Ifinput ports of MB8844 are not changed their state for 20 sec
after START/STOP switch is pushed, output ports R; changes
to H from L, R2 to H from L, and O3 to L from H that micro
motor and DD Motor stop their rotation and plunger solenoid
turns OFF.
2) The protection is released to push START/STOP switch, and one
more push of START/STOP switch actuates full-auto operation.
e
Emergency Stop Operation
1) Ifinput port R turns to H from L (arm lifter is not completely
arised) for some reason, while output port R2 of MB8844 being
L (plunger solenoid is ON ... tonearm is on the way of travel-
ing), the unit shuts down its operation immediately in order not
to damage the disc and the stylus.
2) Once the START/STOP switch is pushed, the protection is re-
leased.
FR-D4
2-5. Operation of Micro Computer Periphery Cir-
cuits
1. Output of A Sensor and B Sensor, and Operation of
Wave Shaping Circuit (See Figs. 2-5, 2-6)
The position of tonearm and end of record disc are detected by A
sensor and B sensor. Output of A sensor is applied to input port Rq
of MB8844 through ICo3a and ICg3b, inverters. Output of B sensor
is fed to Rs through wave shaping circuit composed of TR43, ICoqc
and ICoqd.
A. When tonearm is placed on arm rest.
Since the light beam from LEDo; and LEDg9 are not intercepted by
the screen plate, PT9, and PTg2 (photo-transistors) in A, B sensors
are ON state, therefore input port R4 of MB8844 and input gates 8,
9 of ICoqc are H that output gate 10 of ICgqc becomes L. As input
gate 12 of ICgqd is L, output gate 11 is H. Resultly both input ports
Ry, Rg are H while tonearm is placed on arm rest.
B. When tonearm is left from arm rest
Since the light beam from LED; and LEDog are intercepted by
screen plate, PT9; and PTg2 are OFF state, therefore input port R4
and input gates 8, 9 of ICgqc are L, output gate 10 of ICgqc is H. As
output of PTg2 is fed to base of TRy3 through Cog, the collector
voltage of TR43 is not changed except the period while PT re-
peating ON and OFF (during detection of record end) that input
gate 13 of ICoqd is H and its output gate 11 is L. Resultly, both
input port Ra, Rs are L when tonearm is left from arm rest.
Fig. 2-5 Configuration of Wave Shaping Circuit
+5V
A-SENSOR
LEDO1 PTO
B-SENSOR +5V
LEDO2 pTo2
Fig. 2-6
Stylus Position
Lead-out Groove
a
Recorded Groove
|
@
Output
Waveform
of
||
Input
Waveform
of
TR13
fh
© Output Waveform of TR13 —_—_—— |||
© Output Waveform of ICO4d ||)
ake
Less than 1.3sec(33rpm)
Less than 1.0sec(45rpm)
FR-D4
C. When tonearm is at lead-in position of 30 cm or 17 cm
disc.
Only PT9; of A sensor turns ON and input port Rq4 of MB8844
changes to H from L, and Rg is kept to be L. By the first rise up
signal (L +H) through R4, MB8844 detects tonearm reaching lead-
in position of 30cm disc and the second rise up signal (L +H),
lead-in position of 17 cm disc.
D. Detection of record end
When stylus of cartridge reaches 62 mm before center of platter,
PTo2 of B sensor repeats turning ON and OFF to be lightened
through slit C (Fig. 2-3) and outputs signal as Fig. 2-6 (A). Output of
PTo2 is fed to input gate 13 of ICggd through Coq, TR,3 and al-
though fed to input gate 9 of ICgqc. At this time, input gate 8 of
ICogc is L since PTo; is kept OFF that output gate 10 becomes H
regardlessly to the input gate 9. Thus ICgqgd performs as the same
function of inverter against the signal applied to input gate 13 with
input gate 12 being H. Resultly when the signal with its waveform
shown in Fig. 2-6 © is applied to input gate 13, the output wave-
form of gate 11 is the square waveform as shown in Fig. 2-6 ©.
The term of this square wave is less than 1.3 sec when 33 rpm and
less than 1.0 sec when 45 rpm.
2. Micro Motor Control Circuit (See Fig. 2-7)
Micro motor control circuit is not only for driving the micro motor
to rotate clockwise or counterclockwise according to the signals
from output ports Ro, Ry of MB8844 but also for cancelling inartia
occurring when its clockwise rotation is stopped. During output
ports Ro, Ry being H state, the rotation of micro motor is stopped.
Clockwise rotation is performed when Rg is L, and counterclock-
wise rotation when R, is L. The configuration of micro motor con-
trol circuit is shown in Fig. 2-7.
A. Clockwise rotation of micro motor (corresponding to
returning of tonearm or elevation of arm lifter)
The state of ICgsa ~ ICggd in the control circuit are indicated by
@), 5) as Fig. 2-7 while rotation of micro motor is stopped. If Ro
turns to L from H, output gate 3 of ICgsa becomes H from L, how-
ever, input gate 5 of ICgsb is kept to be H that outputs of ICgsb
and ICosd are not changed. Resultly TRy1 is ON and TRog, TRoe6
are OFF state.
On the other hand TRio turns OFF with Rg changing to L from H
that TRog, TRo7 turn ON. Therefore a current flows successively
from TRo7 > micro motor > TRog and micro motor starts clock-
wise rotation.
Fig. 2-7 Configuration of Micro Motor Control Circuit
+5V
TRO8
ON
Note: ® and D in this Fig. indicate the voltage level of input and output
gates of I1CO5a ~ ICOSd when the micro motor is stopped. ON, and
OFF in Fig. above indicate the state of TRO6 ~ TR11 when the micro
motor rotates clockwise.
B. Stop operation from clockwise rotation
When Rg turns to H from L and micro motor is about to stop from
clockwise rotation, the mono-stable multivibrator composed of
ICosa and ICgsb is activated to flow a current so as to rotate micro
motor counterclockwise for 10 msec that the rotation caused by
micro motor inartia is cancelled. While micro motor is rotating
clockwise, the inputs gate 1, 2 of ICosa are kept L and output gate
3 is H, however, if Ro turns to H from L, output gate 3 becomes
L from H that the voltage at point @ becomes 0 V instantaneously
and outputs of ICgsb, ICosd are inverted. But Cyq is charged
through R39 that voltage at point (A)reaches threshold level of ICosb
10 m sec after the voltage at point @ to be dropped instantane-
ously, therefore input gate 5 of ICgsb becomes H and input and
output levels of ICgsb, ICogd return to initial state. The period
10 msec, while the voltage at point @ is lower than the threshold
level, output gate 4 of I!Cosb is H, output gate 10 of ICosd is L that
TRy is OFF, TRo9, TRoe are ON, which makes a current path of
TRog > micro motor > TRog. Resultly, a counterclockwise torque
is generated to the micro motor to cancel the rotation caused by
inartia.
C. Counterclockwise rotation (corresponding to lead.in
operation of tonearm)
Since output port Rg of MB8844 is kept H and R, is L while micro
motor rotates counterclockwise, TRy9 isON, TRo7, TRog are OFF,
output gate 11 of ICogc is H, output gate 10 of ICgsd is L, and
TR, is OFF state. Therefore TRo¢g, TRog are ON state and a cur-
rent flows successively from TRog — micro motor > TRog that
micro motor rotates counterclockwise.
3. Start/Stop Circuit for DD Motor (See Fig. 2-8)
Start/Stop of DD Motor is controlled by output port O3 of MB8844,
TRo3 and ICoge on circuit board S-0030 and switching transistor
Qio on DD Motor control circuit board 184D. When output port
O3 of MB8844 becomes H, collector voltage of TR 13 is decreased ,
output of ICoze, inverter, is H, and switching transistor Qy9 on tir-
cuit board 184D is ON. Therefore, normal bias voltage is appliedto
the control transistors Qoq ~ Qo6 on circuit board 184D and DD
Motor control circuit is actuated to rotate the DD motor.
Fig. 2-8 Start/Stop Circuit for DD Motor
Fig. 2-9 Relation between input and output of
NAND gate and NOR gate
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