Sansui P-M7 - Signal Functions (E3, F2); Arm Servo and Sensitivity Control; Microcomputer Output Circuits

P-M7
e@ £3 signal
The E3 signal is a signal to detect the size and the presence or ab-
sence of a disc. In the tone arm lead-in operation, if the E3 signal is
generated (changes from a L-voltage level to a H-voltage level) (in
this case, the input port pin No. 4 of the microcomputer changes
from a H-voltage level to a L-voltage level) when the A, B and C
sensors are generating the respective signals as depicted within the
zones (A) ®) and © shown in Fig. 2-3, the respective disc sizes of
30cm, 25cm and 17cm are selected.
After the E3 signal has been generated within the zones@,®)and©
shown in Fig. 2-3, the tone arm stops moving horizontally and next
comes down when the A sensor generates a L-voltage level signal (in
this case, the input port pin No. 26 of the microcomputer changes
to a H-voltage level) or a H-voltage jevel signal (in this case, the
input port pin No. 26 of the microcomputer changes to a L-voltage
level). Further, in the case where no E3 signal is generated within
the zones@,® and © it is determined that there is no disc on the
turntable.
@ F2 signal
Being different from the E2 and E3 signals, the F2 signal is a signal
to indicate that the F sensor detects a lead-over groove when the
stylus is tracing a music ona record disc.
The F2 signal serves as follows:
The fead-over groove of each music is detected in the automatic
music selection operation. In the case where the last music ona re-
cord disc is selected, the instant the last lead-over groove (lead-out
groove) is detected, the F2 signal changes from a L-voltage level to a
H-voltage level (in this case the input port pin No. 33 of the micro-
computer changes to a L-voltage level, so that the tone arm begins
to return.
Fig. 2-3
Position Guide
A SENSOR
B SENSOR
C SENSOR
B SENSOR | 27
C SENSOR | 28
E3 SENSOR | 4
Selection Z Selection
77cm
Zone Zone Selection Zone
17cm Play
30cm Play
D. Arm Servo Sensor
While
the
stylus
is
tracing
a
music
on
a
disc,
it
is
necessary
for
the
stylus
to
be
in
contact
with
the
disc
at
a
right
angle
to
the
modu-
lated
glooves
formed
in
the
disc.
The
arm
servo
sensor
detects
stylus
inclination
from
a
right
angle
to
the
modulated
grooves,
while
the
stylus
moves
on
a
disc.
The
incli-
nation
angle
of
the
stylus
is
checked
by
a
photo
interaptor
of
the
arm
shaft
bearling
and
two
photo
couplers
(fQ8
and
fQ9).
When
the
stylus
inclines
from
the
right
angle,
the
photocoupler
fQ8
or
fQ9
is
turned
on
according
to
the
direction
in
which
the
stylus
inclines,
in
order
to
activate
the
analog
switch
f1C6.
In
response
to
the
signals
from
the
photocouplers,
the
micromotor
(il)
rotates
clockwise
or
counterclockwise
in
order
to
control
the
tone
arm
so
as
to
be
in
contact
with
the
modulated
groove
at
a
right
angle.
E. Music Selection Sensitivity Switching Circuit
The automatic music selection operation must be accurate, without
producing any positioning error when moving down the tone arm
onto a disk, even if there are various dimensions in the width of
lead-over groove.
This music selection sensitivity switching circuit can adjust the sen-
sitivities of the E2 and F2 signals at the same time. As shown in
the block diagram, the reference voltage applied to the comparator
is adjusted to three stages by using a sensor sensitivity selector
switch.
2-4. Microcomputer Output Peripheral Circuits
A. Micromotor control circuit
1. Operation of tone arm horizontally driving micromotor (1)
The
micromotor
operates
according
to
the
tone
arm
up:
or
down-condition as follows:
@ Where the tone arm is up;
When
the
pin
No.
22
of
the
microcomputer
becomes
a
L-voltage
level, the micromotor (1) rotates counterclockwise to perform
the
lead-in
operation.
On
the
other
hand,
when
the
pin
No.
23
of
the
microcomputer
becomes
a
L-voltage
level,
the
micromotor
(I) rotates clockwise to perform the lead-out operation.
@ Where the tone arm is down;
When
the
tone
arm
is
in
a
down-state,
the
micromotor
(1)
rotates
clockwise
or
counterclockwise
in
response
to
the
output
signal
from
the
arm
servo
sensor
(fQ8
and
fQ9)
to
control
the
tone
arm.
Further,
when
the
tone
arm
is
down
(in
playing
a
music),
since
the
pins
No.
6
and
No.
12
of
the
analog
switch
become
a
L-
voltage
level,
the
micromotor
(1)
does
not
rotate
in
response
to
the
output
signal
from
the
pins
No.
22
and
No.
23
of
the
micro-
computer.
2. Operation of tone arm vertically driving micromotor (I)
When
the
pin
No.
24
of
the
microcomputer
becomes
a
L-voltage
level,
the
micromotor
(I)
rotates
counterclockwise
to
move
the
tone
arm
up
or
down.
If
the
UP/DOWN
key
is
depressed
while
the
tone
arm
is
moving
up
or
down,
the
pin
No.
25
of
the
micro-
computer
becomes
a
L-voltage
level
and,
therefore,
the
micro-
motor
(II)
rotates
clockwise
to
move
the
tone
arm
up
or
down.
B. 33 1/3 and 45 rpm Automatic Selection Circuit
According
to
the
size
of
a
disc,
the
revolution
speed
(33
1/3
or
45
rpm)
of
the
turntable
is
automatically
determined.
When
the
E3
sensor
detects
a
30cm-
(25cm-}
dia.
disc
and
a
17cm-dia.
disc,
the
pin
No.
20
of
the
microcomputer
outputs
a
L-voltage
level
signal
for
the
30cm-
(25cm-)
dia.
disc,
and
a
H-voltage
level
signal
for
the
17cm-dia.
disc.
This
output
signal
is
inputted
to
the
pin
No.
10
of
the
DD
motor
control
IC
(TC
9142P
:
elC1)
via
the
speed
selector
switch
(fS2).
The
turntable
rotates
at
a
speed
of
33
1/3
rpm
when
the
pin
No.
10
of
elC1
is
at
a
L-voltage
level,
and
at
a
speed
of
45
rpm
when
the
pin
No.
10
of
elC1
is
at
a
H-voltage
level.
The
relationship
between
the
speed
selector
switch,
the
record
disc
size,
and
the
revolution
speed
is
listed
in the
following
table:
SPEED SELECTOR RECORD SIZE
Sw(fS2) 30, 25cm-dia. | 17cmrdia.
MB8841 Pin No. 20 H
NORMAL TC9142P Pin No. 10 | H
Speed (rpm)
| wB3e4i Pin No. 20
INVERSE TC9142P Pin No. 10
Speed (rpm)