R-2000
CIRCUIT
DESCRIPTION
4} Third
local oscillator (L03}
This circuit consists of
PLL
IC2:
MN614
7C
which in-
corprates a 5
kHz
PLL
and
mixer.
One
VCO
is
provid-
ed; the frequency range
is
39.505
,...,
44.500
MHz
and the dividing ratio range
is
7901
,..,
8900.
This
PLL
circuit
is
composed of
VCO
Q 11:
2SC
1923,
PLL
IC2:
MN614
7
C
and
a
loop filter
consisting of
08,
09
and
010:
2SC
1775.
The
VCO
output
is
buffered
(01
2},
divided
1/100
to
395.05
,..,
455.00
kHz
by
IC3:
MN54459L,
buffered
(013)
and mixed with the
9 MHz reference
signal by IC4:
SN
16913P
to obtain
the
9.39505
,..,
9.445 MHz third
local oscillator
fre-
quency. This
is
filtered
(CF
1)
and
amplified
(Q
15},
then sent to the Receiver unit.
5)
Unlock
muting
The output from
PLL
IC2
pin 2 (unlock) becomes
an
unlock signal
through
IC21:
TA7324P
and
071.
and
is
used to
control
the audio muting circuit
on
Switch
unit
"B''
to
reduce or eliminate any pulse
noise which
may
be
generated when the frequency
is
changed
and
the
PLL
momentarily resets.
2. Control unit
EN1
EN2
IC9
Q)
IC9
@
IC9
©
IC9
@
1}
Rotary encoder input circuit
On
the Encoder
unit,
a
50
slit
rotary disc and 2 pho-
tointerruptors generate 2 clock
signals having a
90°
phase difference; which
are
input to the Control
unit
via
the
EN
1
and
EN2
lines.
These
clock signals
are
waveform shaped by
IC6, quadrupled
by
the gate cir-
cuit consisting of
IC7
and 8 (the
50
pulse/rev signal
is
changed to a
200
pulse/rev signal),
and
applied
IC
12,
through
Flip-Flop
IC9
1
/4
to the microprocessor pin
No.
39
(T1
port). At the same time, the encoder's rota-
tional
dirction
is
detected from the
clock
pulses by the
FF
circuit
IC9
1/4
and
is
input to microprocessor pin
29
(Port
37).
The
waveforms at each point
are
shown
in
Fig.
1.
Encoder rotates for Rotates
for
Down.
-Up
operation-1--
Operation -
Encoder
output
1
E
needer
output
2
IC7.8
Gate
output
UP/DOWN
signal
Microcomputer
T1
input
Fig. 1 Encoder output
to
micro-processor
input timing and
waveforms
2)
Program scan circuit
IC
10
on
the Control circuit
is
an
astable
multivibrator
circuit
controlled
by the
PG.
SCAN
switch. Both its
output, and the
clock signal
are
applied to the micro-
processor T 1 port.
During scan, the
multivibrator oscillators
output pulse
train
is
accessed by
!Cs
9 1 /4,
10
1
/4
and
11
1 /2,
while the
oscillator
stops
in
the
HOLD
mode and
only
the Encoder clock
pulse
is
available.
The
oscillator frequency
is
determined by C
1
7
3,
C
174. R
145
and
VR
1.
When the tuning speed
is
SLOW or
MID,
the
oscillator frequency
is
approximate-
ly
10
,..,
18
Hz.
When it
is
FAST.
034
turns
on
and
the oscillator frequency
is
approximately 5
,...,
9
Hz.
3}
Clock
circuit
A
1
kHz
clock signal
is
output from
PLL
IC2
(pin
6),
waveform shaped
by
IC
17 1
/4
and
applied to the mi-
croprocessor
INT
port (pin
No.
6)
to count the time.
When the
HOUR
and
MINUTE
switches are de-
pressed
simultaneously
the time
display
shows
00:00.
In
CLOCK
1
mode,
the time
display
stops
flashing
and the
clock
begins counting the seconds
(which
are
not shown} when the switches are de-
pressed. When the
display
is
flashing, the
HOUR
and
MINUTE
switches cannot
be
used to set the time.
When the Function switch
is
set to any position other
than
FREQUENCY,
depressing the
HOUR
switch
will
increment the
HOUR
digit by
one.
When the
HOUR
switch
is
held
ON,
the Hours digit increases contin-
uously.
The Minutes digit does not change during
HOURS
set.
Each time the
MINUTE
switch
is
depressed. the Min-
utes digit increases by one. When the switch
is
held
ON,
the Minutes digit advances.
The
Hours digit does
not change during Minutes set.
To
program the timer, set the timer
ON
time
and
place
the timer switch
ON.
Receiver power remains off
until
the timer preset time
is
reached, when the relay
is
activated and the power
is
switched
on.
When the timer
OFF
time
is
programmed, the power
is
turned off at that preset time. When the timer switch
is
ON,
the power switch
is
inoperative.
The
timer
relay
output
is
available
at the Remote
control
terminals
on
the rear
panel.
4) Microprocessor power supply circuit
When the microprocessor IC12: µPD80C49C
1s
in
operation, 5V
should
be
applied to
Vee
pin
No.
40.
When the microprocessor
is
in
the back-up standby
mode,
2V
should
be
applied. When the power switch
is
turned off,
035
and
036
change the
level
of
RES!:T
pin No. 4 to
low
to protect the
RAM,
the V
DD
pin
No.
26
becomes low to stop the
oscillator
and the con-
tents
of
the
RAM
are
maintained
by
the
low standby
voltage
(Vee).
·
When the power
is
turned
on,
5V
is
applied
to the
Vee
pin. the V
DD
pin becomes high while the
RESET
pin
is
held low
to activate the
oscillator,
then the
RESET
pin
returns to a
logic
high and the program
is
reset.
Oscillator
stop
Oscillator
starts
::DET="q.
~
·-
Stai)mzed
oscillating
-----
penod
Fig. 2 Micro-processor
power
supply circuit
5
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