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CIRCUIT
DESCRIPTION
a.
POWER
SUPPLY
.
When the POWER switch is turned on, all circuits are sup-
plied with voltage from the AC Adapter.
The circuits supplied
with voltage are of three types : cir-
cuits supplied
directly
with a voltage of + 9V, circuits sup-
plied with a constant-voltage
of + 5V, and circuits supplied
with a constant-voltage
of + 7V.
1., The circuits supplied
directly with a voltage of + 9V
(1) Audio amplifier
(ICI and IC2)
(2) Play Drive and Rewind Drive circuits
(3) Backspace
circuits
(4) Erase Head Drive circuits
(5) TEL. Record / Dictate circuit
2. The circuits supplied
with a constant-voltage
of + 5V
(1) MPU (Microprocessor
unit) lC3
(2) Cue Tone Signal Record circuit
(2) Cue Tone Signal Detect circuit
(3) Rotation Detection
circuit
3. The circuits supplied
with a constant-voltage
of + 7V
(1) Motor Governor circuit
b.
c.
PLAYBACK
CIRCUIT
When the PLAY button is pushed, pinl
(PDO) of IC3 goes
to low, as does pin9 of IC3. This activates the Play Drive
Circuit composed
ofQ12, Q13 and the Play Solenoid
(SL1 ).
A signal from the tape is played back according
to the fol-
lowing process :
Record / Play Head (HD1-1 ) + Pre-amplifier
(IC1 pin6 +
IC1 pin3) + Tone Control (VR1 ) + Volume
Control (VR2)
+
Power Amplifier
(IC2 pin3 +
IC2 pin5) +
Earphone
Jack (J3) + Mic. / Speaker Switch (S2-2) + Speaker (SP1 )
When
playing
back (including
fast forward
and rewind),
the voltage
will not be supplied
to pin9
of the Pre /
Record Amplifier
(IC1 ).
Also, the muting
transistor
Q4 goes off.
Moreover,
the
OSC transformer
(Tl ) is carried out muting
through
Q31,
Q32 and Q33.
RECORDING
CIRCUIT
A signal
from
either
the Microphone
(Hand
Control)
or
TEL. Record Jack (J2) is recorded
on the tape according
to the following
process.
Pre / record Amplifier
(IC1 pin9 + IC1 pin7) + Record /
Play Head (HD1-1)
A voltage of approximately
3.2V is supplied
to pin9 of the
Pre / record Amplifier
(iCl)
at this time, and IC1 will be
changed
to the recording
mode.
Then
pin16
of IC3
goes
to high
(approx.
1.3V),
Q13
turns
on, and
the
Record
Sig-
nal from
ICI
pin3
is muted
and
howling
prevented.
When
recording,
Q9
turns
on and
voltage
is supplied
to
and
activates
the
Bias
Circuit
composed
of Q6
and
T1.
At the same time, Q31 and Q32 go off when Q33 goes off
and then the OSC transformer
(T1 ) muting is eliminated.
d.
e.
f.
CUE
TONE
SIGNAL
RECORD
CIRCUIT
w
The Cue Tone Signal transmits
for approximately
1.6 sec.
emitting
about 130Hz rectangular
wave from pinl 8 (PF3)
of IC3.
This signal passes through
a filter composed
of
R109, C50, R1 07, C57, RI 04, R103 and C55, is boosted
at Q23 and Q22, and is recorded
onto the tape from the
Search track of the Record/
Play Head (HD1 -2).
While the Cue Signal Tone is being emitted
(approx.
1.6
sec.), pin19 of IC3 goes to high (approx.
3.5V) and Q29
and Q5 turn on.
The Cue Tone Signal is recorded
onto
the tape because
Q29 is on, and the circuit for the voice
recording
is muted because Q5 is on.
CUE
TONE
DETECTION
CIRCUIT
This circuit operates only during fast forward and rewind.
The Cue Tone Signal recorded
on the tape is played back
according
to the following
process :
Record / Play Head (Search Track HD1 -2) + Cue Tone
4
Detection
Circuit (IC4 pin2 + IC4 pin7) + Q24 + Q26 +
Q27 + Q28 + IC3 pin27 (PC2).
During fast forward the input Cue Tone Signal goes to ap-
proximately
400 Hz.
This signal
is boosted
at IC4 and
when over Q28 turns on by means of Q24, Q26 and Q27.
When Q28 turns on, pin27 of IC3 (PC2) goes to low, and
the signal is picked up by the MPU (IC3) as the Cue Tone
Signal.
Pin9 (PEO) of IC3 goes to high (approx.
1.2V) for
approximately
2 seconds,
releasing
the Play Solenoid.
At
the same time, pinl 5 (PFO) of IC3 goes to high (approx.
2V) and the Motor (Ml)
drops from high speed to normal
rotation.
During rewind the input Cue Tone Signal goes to approxi-
mately 650 - 2200 Hz. This signal is boosted at IC4 and
when over Q28 turns on by means of Q24, Q26 and Q27.
When Q28 turns on, pin27 of IC3 (PC2) goes to low, and
the signal is picked up by the MPU (IC3) as the Cue Tone
-
Signal.
Pinl 2 (PE3) of IC3 goes to high (approx.
1.2V),
releasing the Play Solenoid
(SL1 ).
ALARM
SIGNAL
The Alarm
Signal
is a 650Hz
rectangular
wave emitted
from pin17 (PF2) of IC3.
This signal passes R27, C25,
R26 and R25 and enters pin 3 of the Power Amplifier
IC2,
where
is boosted
and emitted
from the speaker
as an
alarm signal.
There are 4 types of alarm signals :
(1) No Cassette Alarm
., . . . . . .
sounds continuously
(2) ASOAlarm
. . . . . . . . . . . . . . . . . . .
approx.4
sec.
(3) Cue Tone Record Alarm
. . . . . . .
approx. 1.6 sec.
(4) Cue Tone Signal Detection Alarm
. .
approx. 2 sec.
-9-
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