Sansui FR-D4 - Timing Chart of Micro Computer MB8844; Practical Operation and Timing Chart

FR-D4
Fig. 2-4 Timing Chart on Input and Output of Micro Computer
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2-4. The practical Operation of Turntable and
Timing Chart of Micro Computer MB8844
(See Fig. 2-4)
1. Full-Auto Operation
A. Start > Lead-in > Return > Stop
in case of 30 cm disc, 33 rpm.
1) When input port Ko of MB8844 turns to H from L to push
START/STOP switch, output port Ry becomes L (which makes
micro motor rotate counterclockwise), output port Ry becomes
L (plunger solenoid is ON), that tonearm starts moving in lead-in
direction. 200 msec after Kg becomes H from L, output port O3
turns to H from L to start DD Motor rotating. As soon as tone-
arm moves lead-in direction, input ports Ra, Rs become L since
the light beam from LED is intercepted by the screen plate in A,
B sensor.
2) When tonearm reaches lead-in position over the 30 cm disc, light
passing through slit A (Fig. 2-3) makes photo-transistor of A
sensor ON, thus input port R4 of MB8844 becomes H from L.
Sequently to the Rq from L to H, R turns to H from L (plunger
solenoid is OFF), Ry becomes H from L, Rg becomes L from H
(micro motor rotates counterclockwise) that the torque of micro
motor is transmitted to the lifter cam which lowers arm lifter.
Following to the rotation of lifter cam, the button of D sensor is
depressed by the lifter cam and R» becomes H state.
3) After arm lifter is completely lowered to rotate lifter cam, the
button of C sensor is released to enter into the notch of lifter
cam. Therefore input port Rg of MB8844 becomes L from H
and Ro becomes H from L that rotation of micro motor is
stopped.
4) When stylus of cartridge proceeds till 62. mm from center of disc,
the photo-transistor of B sensor repeats turning ON and OFF
alternately that voltage level H and L is alternately applied to
input port Rs of MB8844. After stylus enters to lead-out groove,
the applied voltage to Rs repeats H, L in the term less than 1.3
sec, which is detected as the end of record disc that output port
Ro turns to L from H (micro motor starts counterclockwise
rotation) and arm lifter is arised.
5) With the complete rise of arm lifter, input port Rz becomes L
from H to be released the button of D sensor. Sequently to the
R> from H to L, R2 turns to L from H (plunger solenoid turns
ON) that clutch plate is depressed to TA drum, and tonearm
moves return direction.
6) When tonearm is reached arm rest, photo-transistors of A,
B sensors are lightened that they turn on, which makes input
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ports Rq, Rs of MB8844 turn to H. 0.85 sec after this, Rg be-
comes H from L (micro motor stops), R2 is H from L (plunger
solenoid turns OFF), and O3 becomes L from H (DD Motor
stops).
Start > Lead-in > Repeat > Cut
in case of 30 cm disc, 33 rpm.
When Repeat switch is pushed at once, the input port Ky of
MB8844 turns to H from L, and output port Rg to L from H
(repeat indicator LED 702 becomes luminous).
If START/STOP switch is pushed followingly to the above, tone-
arm moves as the same process with A-1) ~ 6) and returns to its
rest after finishing record playing.
When tonearm reaches just before arm rest, photo-transistors of
A, B sensors turn ON, which causes output port Rg to change to
H from L (clockwise rotation of micro motor is stopped) and R;
to be L from H (micro motor rotates counterclockwise) that
lead-in operation is performed.
Since output port Rg of MB8844 becomes L from H (micro
motor starts clockwise rotation) to push the START/STOP
switch once more, arm lifter is arised immediately. At this time
the repeat function is released that output port Rg becomes H
from L and repeat indicator stops lighting.
The following operation is carried out in the same manner of
A.5), 6), and tonearm returns to arm rest.
Start > Lead-in > Return > Repeat
in case of 17 cm disc, 45 rpm.
When repeat switch is pushed, input port K, of MB8844 turns to
H from L instantaneously with Rg from H to L. (repeat indica-
tor starts lighting) :
Tonearm moves as the same process as A-1) after START/STOP
switch is pushed.
MB8844 detects whether tonearm reaches lead-in position of
17 cm disc by the second rise up signal (L +H) applied to input
port Rq and makes output ports Rg from H to L, Ry from L to
H and R2 from L to H to lower the arm lifter.
When stylus reaches lead-out groove, signals H and L are alter-
natively applied to input port Rs as a record end signal in the
term less than 1.0 sec. After detecting record end, tonearm re-
turns in the same manner of A-4), 5).
When tonearm reaches just before arm rest to turn ON photo-
transistors of A, B sensor, both inputs R4, Rs of MB8844 be-
come H that output port Ro turns to H from L, Ry to L from H
(micro motor starts counterclockwise rotation) and lead-in func-
tion is performed again.