Sony TC-730 User manual

Power Requirements:
Power Consumption:
Track System:
Ree! Size:
Tape Speed:
Recording Time:
(with 1,800 ft. tape)
Frequency Response:
Signal-to-Noise Ratio:
Flutter and Wow:
Harmonic Distortion:
Recording
Bias Frequency:
Inputs:
SPECIFICATIONS
AC 100, 110, 120, 127, 220 or
240 V 50/60 Hz
AC 120W
4—track 2—channel stereo and mono
7° (48 cm) or smaller
7 \/2 ips (19 cm/s), 3 3/4 ips (9.5 cm/s),
1 7/g ips (4.8 cm/s)
Tape speed 4-—track stereo 4—track mono
vd Vo ips 1.5 hrs 3 hrs
(19
cm/s)
3 3/4 ips 3 hrs 6 hrs
(9.5 cm/s)
(with SONY SLH tape)
20 ~ 30,000 Hz at 71/2 ips (19 cm/s)
20 ~ 20,000 Hz at 33/4 ips (9.5 cm/s)
(with standard tape}
20 ~ 25,000 Hz at 71/2 ips (19 cm/s)
20 ~ 17,000 Hz at 34/4 ips (9.5 cm/s)
30 ~ 9,000 Hz at 17/g ips (4.8 cm/s)
56 dB (with SLH tape)
53 dB (with standard tape)
0.06 % at 71/2 ips (19 cm/s)
0.1% at 39/4 ips (9.5 cm/s)
0.2% at1 ’/gips {4.8 cm/s)
1.2%
Approx. 160 kHz
Two MIC Inputs
Impedance
Maximum sensitivity
: low impedance
: —72 dB (0.2 mV)
Outputs:
Maximum
Power Output:
Built-in Speaker:
Semiconductors:
Dimensions:
Weight:
Two AUX Inputs
Impedance
Maximum sensitivity
REC/PB connector
Input impedance
Input level
Two LINE Outputs
Load impedance
Output level
HEADPHONE Output
Load impedance
Output level
REC/PB connector
Output impedance
Output level
Two EXT SPKR
Load impedance
Output level
E Model
STEREO
TAPECORDER
: 100 kQQ
: —22 dB (62 mV)
10kQ
: —33 dB (17.4mvV)
: 100 kQ2
: OdB (0.775 V)
BQ
: —36 dB (12.3 mV)
at LEVEL’*1”
—28 dB (30.8 mV)
at LEVEL’ “2”
: 10kQ2
: OdB (0.775 V)
:8Q
: 17 dB (5.6 V)
3.7 W x 2 with built-in speakers
15 Wx 2 with external speakers
4x6 (10x 15cm) x2
impedance 32 (2
51 transistors, 25 diodes and 1 integrat €d circuit
21 (W) x 19 5/g (H) x 8 15/46" (D)
(533 x 498 x 227 m)
51 Ib 13 oz (23.5 kg)
‘SERVICE MANUAL,

Section
N
GENERAL DESCRIPTION
1-1.
1-2,
1-3.
TABLE OF CONTENTS
Title
Specifications ..........
Block Diagram .........
Major Parts Locations ......
Switch Location. ........
CIRCUIT DESCRIPTION
Record Amp Circuit
Muting Circuit
System Control
3-1.
3-2.
3-3.
3-4,
3-5.
Ac’Servo Circuit
4-1. Priciple. ace. 4.5 See Bo SS
4-2. Servo Amplifier Operation. ...
4-3. Motor Speed Deviation from
Intended Value .........
Sequence of Switch Operation. . .
DISASSEMBLY
2-1. Cabinet Removal... ......
2-2. Head Deck Removal. ......
2-3. Record Equalizer Circuit Board
Removal. ..........
2-4. Reverse Switch Circuit Board
Brake Solenoid PM602 .....
Reel Motor Circuit... .....
Pinch Roller Solenoid PM601 .. .
Solenoid Operating Voltage ....
Removal
ADJUSTMENT PROCEDURES
3-1.
3-2.
Mechanical Adjustments. ... .
Electrical Adjustments .....
Section
Title
4. DIAGRAMS
4-1.
4-1-1.
4-1-2.
4-2.
4-2-1.
4-2-2.
4-2-3.
4-2-4,
4-2-5.
4-2-6.
4-2-7.
4-2-8.
4-2-9.
4-2-10.
4-2-1].
4-2-12.
4-3.
5. ELECTRICAL PARTS LIST
Schematic Diagram .......
Audio Amp and Bias OSC
Circuits 3.05 oe oe Ea
System Control Circuit .....
Mounting Diagram. .......
Record Amp Circuit Board
Speaker Selector Switch
Circuit Board ..........
Tone Control Circuit Board ...
Power Amp Circuit Board... .
Relay Circuit Board .......
Power Supply Circuit Board. . .
Servo Control Circuit Board. . .
Reverse Switch Circuit Board .. .
. 68
Level Diagram
6. EXPLODED VIEWS
6-1.
6-2.
6-3.
6-4.
6-5.
6-6.
6-7.
6-8.
6-9.
7. HARDWARE
Cabinet — top view ~—
Head Deck —topview— ....
Amplifier Chassis Panel
—topview- ..........
Amplifier Chassis — top view — .
Chassis — topview—-(1).....
Chassis — top view — (2)... ..
Chassis — top view —(3).....
Chassis ~ bottom view—- ....
PaCkKin gw ao in2kt Ge eos e esa al
Hardware Nomenclature. ....
When ordering replacement parts, you should use PART NUMBER
listed on the Parts Lists or shown in the EXPLODED VIEW.
The reference number should not be used for ordering purposes.
. 39
. 39
. 41
. 43
. 43
Record Equalizer Circuit Board . . 46
Playback Amp Circuit Board. . .
Bias OSC Circuit Board .....
SOS/ECHO Circuit Board ... .
. 48
.51
. 54
“55
. 56
. 58
. 60
. 63
. 66
67
. 70
77
279
. 81
. 83
. 85
. 87
. 88
. 89
. 90
941
. 91

SECTION 1
GENERAL DESCRIPTION
BLOCK DIAGRAM
1-1.
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1-2. MAJOR PARTS LOCATIONS
Cabinet — Top View —
X-34980-81 X-34970-46
reel panel knob ass’‘y,
ass ‘y, complete AUTO REV
| |
X-34970-47
cover assy, h@ad - rr
X-34970-46
knob assy,
1-5 14-867
switch, slide;
TAPE SELECT (S108)---~-----—-—
1-514-768
switch, lever;
HEADPHONE LEVEL (S109)-------
1-507-282
jack, binaural; :
HEADPHONE (J104)
ack :
Fen R(J202) |
at t
igieaditt \
X-34970-50 AUX-L ——--— | | |
knob (A) ass‘y, i | |
control AUX-R - : |
i of ;
i { |
M Si oe J }
1-524-082-11 EME | | |
meter, VU R(ME2) ———--—________-— {
j
L (S105) R ($205)
1-5 14-836
switch, MONITOR
Cabinet — Side Views —
EXT SPKR
171-536-309
push terminal, —
4P (35701)
1-507-142
Jack, AUX IN
(J101, 201)
171-509-359
connectors,
REC/PB
3-497-237
terminal, GND
171-507-142
tack, LINE OUT
(S703, 203)
1-514-868
switch, lever
ECHO/SSOS (S110)
‘ VOLUME
__ 1-§14-869
switch, lever;
~ MIC-R
X-34980-01
“cabinet assy
SOS/ECHO
X-34980-02
TREBLE knob (B) ass'y,
contro!
BASS
knob (A) ass’y,
control
- ees X-34970-50
SPKR SELECT (S702)
X-34580-22
knob ass’y, selector
1-514-866
switch, seesaw; POWER AMP (S701)
1-507-282
jack, binaural; HEADPHONE (J702)
AUX-R \ X-34970-50
knob (A) ass’y,
control
~R x.34970-45
button ass’y, REC
_. 1-533-048
holder, fuse
1-509-427
socket, power
voltage selector
(VS6071)
UNSWITCHED- -300W--
171-509-341
—- connector, AC
i OUTLET (CNJG071}
1-534-487
cord, power

Chassis — Top View —
X-34970-26
reel table ass’y
1-454-075 ;
solenoid plunger; —_—__7al
pinch roller (PM601) j
8-829-142-20 ———
head, playback
(PP102-4202)
8-828-629-20
head, record/erase
{ERP102-2902)
3-497-207
pinch roller
1-222-497
resistor, variable;
AUX 30 kQ.(D) (R136)
1-222-498 1-524-082-11
resistor, variable; meter, VU (ME7, 2)
MIC 10 k82(D) (R135)
Chassis — Bottom View —
1-441-730 8-833-012-01
transformer, power motor, fan
(T601) (1S-024A]}
8-836-624-07
motor, reel
(UC-624K)
X-34980-51
mounted circuit
board, tone control
X-34980-52
mounted circuit ——-——
board, power amp
X-34980-56
mounted circuit
board, speaker
selector switch
1-454-074
solenoid, plunger;
direction (PM603)
X-34970-61 X-34970-64
mounted circuit mounted circuit
board, record amp _ board, bias osc
8-828-629-20
head, record/erase (ERP 102-2902)
171-221-910
S<— resistor, variable 50 kQ.(C) (ECHO/SOS)
171-221-917
" ggrl- resistor, va-iable 50 kKQ. (A) TREBLE
p 1-221-917
42 resisotr, variable 50 k82.(A} BASS
1-222-499
resistor, variable 500 k82 BALANCE
gael 1-221-917
resistor, variable 50 k82. (A) VOLUME
Y-20410-12-9
counter, tape index
—*1-514-870
switch, rotary;
MODE
1-222-497
resistor, variable,
AUX 30 k91{D) (R236)
1-222-498
resistor, variable,
MIC 10 k§2(D) (R235)
1-454-074
solenoid, plunger;
brake (PM602)
8-836-624-07
motor, reel (UC-624K)
X-34970-66
mounted circuit
board, relay
X-34970-68
mounted circuit
board, servo control
X-34980-53
mounted circuit
board, power supply
8-836-214-01
motor, capstan
(UC-214G)
- X-34970-62
mounted circuit
board, record equalizer
mounted circuit
board, playback amp

1-3. SWITCH LOCATION
S614 (upper side)
PLAY, FF-STOP switch (4)
S605 (lower side)
PLAY, FF-STOP switch (2)
S610 (upper side)
PLAY, FF-STOP switch (3)
S613
i .__.§602 (lower side)
te” PLAY, FF-STOP switch (1)
S604 (upper side)
S620 —~- PLAY-FF, STOP switch (1) .
PLA Y-FF, STOP S612 {lower side)
switch (4) PLAY-FF, STOP switch (2)
= S609
S618 AUTO SHUT-OFF switch
AUTO OFF swit
OFF switch S616
S607
PLAY
switch
(3)
FF switch—
PLAY switch (2)
- S608
PLAY switch (1)
~~ S606
STOP switch
woes SHIT
FF switch (2)
S619 (upper side)
FWD-REV switch (2)
S607 (lower side)
FWD-REV switch (1)
;
3
E
|
!
i

CIRCUIT DESCRIPTION
The following describes operation of main circuit:
1. RECORD AMP CIRCUIT
First stage of the record amplifier comprises
NPN and PNP type transistors connected in parallel.
This circuit improves linearity characteristics of
record amplifier for MIC jack input signals.
Approximately 50 dB linearity can be obtained.,
Therefore, can record signals with greater input level
(approximately —10 dB, 0.25 V to MIC jack) with
low distortion. Linearity for conventional circuit
which has only one transistor is approximately 30 dB.
2. MUTING CIRCUIT
During direction change of tape transport (about
three seconds), from the time when tape stops moving
until tape motion reverses and recoveres to normal
tape speed, B + voltage of bias oscillator is cut off in
record mode and the muting circuits (Q306 and Q406)
of playback amplifier are activated in playback mode.
When turning POWER switch ON, the multivibrator
(Q504 and Q505) is kept stable as follows:
POWER switch is turned ON.
Initial current through C505 turns 0505 ON.
Decreased collector voltage of 0505 turns Q504 OFF.
After C505 has been charged, Q505 base bias is
applied through R507.
0505 is kept ON.
Decreased collector voltage Decreased collector voltage
of Q505 keeps 0306 and of 0505 keeps O506 OFF.
Q406 OFF.
Playback amplifier normal- O503 is kept ON and sup-
ly works. plies B+ voltage to bias
oscillator.
When changing the unit from FWD mode to REV
mode or vice versa, this circuit acts as follows:
FWD— REV REV — FWD
Negative trigger pulse Positive trigger pulse
through D614 turns through D613 turns
Q505 OFF. Q504 ON.
Increased collector voltage
of 0505 turns.0504 ON.
Collector voltage of Q504 decreases.
Current flows through R506 and through R507 and
C505.
C505 discharges for about three seconds. During the
discharge, Q505 is turned OFF by decreased base bias.
Increased collector
voltage of O505
turns Q506 ON.
Increased collector
voltage of Q505
turns Q306 and
Q406 ON.
Q306 and Q406 Q503 turns OFF
ground audio and cut off B+
signals. voltage to bias
oscillator.
After the discharge, current stops flowing through
R507 and C505.
Q505 is turned ON by increased base bias.
0504 is turned OFF.
:
:
j
E
é
:

Bt
From power supply circuit
Q503
Q306 (0406)!
o UPLAY
S614
Muting circu
Collector voltage of Q505 rises for
sTopo PLAY
FF
a =p S103-2
about three seconds when the
meade switch is changed, and then
306 (Q406) turns ON.
D604
Fig. 7.
3. SYSTEM CONTROL
3-1. Brake solenoid PM602
When FWD button is pushed, S608 turns ON.
Then high voltage (about 170 volts dc) rectified by
D604 is applied to PM602 through S605. PM602 is
energized.
3-2. Reel motor circuit
The motor current flows as follows:
46 V or 80 V terminals of power transformer
——» $612 ———» R609 ————-contacts
of relay RY602-——— reel motors M2, M3
—» $610 ————~- 0 V terminal of power
transformer
3-3. Pinch roller solenoid PM601
When S602 is turned ON by solenoid PM602,
high voltage (about 170 volts dc) rectified by D604 is
applied to PM601 through S604. PM601 is energized.
Bt
To bias osc circuit
ral” V (in FWD mode)
OV lin REV mode)
RY601
Muting circuit
3-4. Solenoid operating voltage
Solenoids (for brake, pinch roller, and tape
direction) are energized by high voltage (about 170
volts dc) and kept energized by low voltage (about 30
volts dc).
3-5. S612
This switch supplies a high reel-motor-driving
voltage (80 volts ac) to make strong tape tension in a
starting moment, because of tape slack elimination.
When pressing FWD or REV button, $612 supplies
80 volts ac for about one second unitl pinch roller
solenoid PM601 actuates S612. After solenoid PM601
has actuated S612, S613 supplies 46 volts ac for
normal tape tension.

FF, STOP
REW
right reel motor
self-locking {Turns ON when
contacts of \FWD button is pushed,
RY602
S607
Turns ON when FF
or REW button is
pushed
RY602
FF relay
Fig. 2. Reel motor circuit
4. AC SERVO CIRCUIT
The
Model
TC-730
employs
ac
servo
amplifier
circuit
and
keeps
tape
speed
constant.
4-1. Principle
See
block
diagram
in
Fig.
3.
Motor
speed
determined
by
voltage
Em
can
be
changed
by
voltage
Er.
E (fixed) = Em + Er
When
motor
speed
becomes
faster
or
slower
than
intended
speed
according
to
external
disturb-
ances,
the
intended
motor
speed
can
be
obtained
again
by
changing
voltage
Er,
or
by
changing
resistance
R.
The
frequency
generator
FG
in
the
motor
detects
motor
speed
deviation.
Servo
amplifier
changes
resistance
R
according
to
the
deviation.
TC-730
uses
impedance
R
between
collector
and
emitter
of
tran-
sistor
Q901
instead
of
resistance
R
as
shown
in
Fig.
4.
Impedance
R
can
be
changed
by
the
base
voltage.
The
motor
speed
can
be
kept
stable
by
controlling
the
base
voltage
for
the
motor
speed
deviation.
The
bridge
type
rectifier
comprising
four
diodes
makes
current
flow
through
transistor
Q901
in
the
direction
shown
by
the
arrow
in
Fig.
4.
Efconstant)
SERVO AMP
Fig.
3.
Servo
control
system
block
diagram
SERVO AMP
Fig. 4. Q9017 instead of resistance R
Outline of IC (CX-032})
Q2
Fig.
5.
Servo
amplifier
outline
Ac
4-2. Servo amplifier operation
Servo
amplifier
which
changes
impedance
R
operates
as
follows:
See
Fig.
5
and
Fig.
6.
1)
2)
3)
4)
Sine
wave
signal
generated
by
frequency
ge-
nerator
FG
is
transfered
to
bases
of
Q1
and
Q?2.
Since
base
bias
voltages
of
Q1
and
Q2
are
set
to
saturation
region,
sine
wave
signal
is
waveshaped
to
square
wave
signal
shown
by
(A)
in
Fig.
6.
Square wave signal from Q2 is amplified by Q3,
Q4
and
QS.
It
is
transfered
to
differentiating
circuit
comprising
Cl
and
R1
and
is
wave-
shaped to pulse shown by (B) in Fig. 6.
Then it is transfered to base of Q6.
De
voltage
Vs
stabilized
by
Q12
is
divided
by
R3
and
R4.
Then
it
is
transfered
to
base
of
Q8
and
keeps
the
emitter
voltage
Ek
of
Q8
(also
that
of
Q7)
constant.
Vs also charges C2 according to the time constant
decided
by
C2
and
R2.
The
charged
voltage
is
applied to collector of Q6.
When pulse shown by (B) in Fig. 6 is transfered
to
base
of
Q6,
Q6
repeats
ON
and
OFF
states.
C2
discharges
while
Q6
makes
current
flow
as
shown
by
the
arrow
(1)
in
Fig.
5.
Thus
sawtooth
wave
signal
shown
by
(C)
in
Fig.
6
is
obtained
at collector of Q6.
—10—
5)
6)
4-3.
1)
The sawtooth wave signal is supplied to base of
Q7. Since the emitter voltage Ek is kept con-
stant, Q7 turns ON only when the peak value of
sawtooth wave signal is greater than Ek. When
Q7 turns ON, the negative pulse shown by (D)
in Fig. 6, appears at collector of Q7.
This pulse is amplified by Q9, Q10 and Q11,
and its polarity is inverted. The positive pulse
is transfered to the integrator comprising R5
and C3, and is waveshaped as shown by (E) in
Fig. 6. After being amplified by Q13 and Q14,
it is transfered to base of Q901. And this base
voltage changes impedance between collector
and emitter of Q901 and controls motor speed.
Motor speed deviation from intended value
When motor speed becomes faster (Fig. 7);
Switching speed of Q6é becomes faster since
frequency of frequency generator FG increases.
Collector voltage of Q6 is grounded before it
becomes greater than emitter voltage Ek (con-
stant) because of short charging time for C2.
The peak value of the sawtooth wave signal at
base of Q7 is less than Ek. Thus Q7 turns OFF,
and base voltage of Q901 decreases since the
pulse is not supplied to base of Q9. When

2)
3)
impedance
R
becomes
greater,
motor
voltage
Em
decreases
and
motor
speed
decreases
to
the
intended.
When motor speed becomes slower (Fig. 8) ;
Switching
speed
of
Q6
becomes
slower
since
frequency
of
frequency
generator
FG
decreases.
Collector
voltage
of
Q6
is
grounded
after
it
becomes
greater
than
emitter
voltage
of
Q7
because
of
sufficient
charging
time
for
C2.
The
peak
value
of
the
sawtooth
wave
signal
at
base
of
Q7
is
higher
than
Ek.
Thus
Q7
turns
ON
for
T
seconds,
and
base
voltage
of
Q901
increases
since
the
pulse
is
supplied
to
base
of
Q9,
when
impedance
R
becomes
less,
motor
voltage
Em
increases,
and
motor
speed
increases
to
the
intended
speed.
Thus
by
changing
the
time
T
motor
speed
is
controlled.
.
Time T is determined by charging-time of C2
(the
inclination
of
the
sawtooth
wave).
In
this
ac
servo
circuit,
the
time
constant
(C2
x
R2)
for
charging
time
is
determined
by
R2
for
the
specified tape speed.
Circuit operation when motor starts running;
Just after the power switch is turned ON, Q6
is still turned OFF since signal is not supplied
from the frequency generator (motor. is not
running). C2 is charged rapidly, and greater
voltage
than
Ek
is
applied
to
base
of
Q7.
When
base voltage of Q901 increases, ac voltage is
FG output signal
approx. 900 Hz at
19 cm/s (7 % ips)
collector
of Q2
base
of Q6
collector
of O6
collector
of Q7
base
of Q901
Fig. 6. | Waveform at each point
qe:
applied to the motor and the motor starts
running rapidly. In the FF mode, the servo
circuit does not work and ac voltage is applied
to the motor directly.
Then motor rotates at full speed.
FG output signal
(short cycle)
collector
of Q2
base of O6
(short cycle)
|
base of Q7
Ek
LAA (peak value lower
than Ek}
no pulse collector of Q7
at base of Q907
(decreases)
Fig. 7. When motor speed becomes faster
(long cycle)
collector
of Q2
base of Q6
(long cycle)
base of Q7
(peak value
base of Q901
(increases)
Fig. 8. When motor speed becomes slower
FG output signal
higher than Ek}
collector
of Q7
SEQUENCE OF SWITCH OPERATION
Note: The number in circle shows the sequence of
switch operation when the mode is changed.
FWD Button Is Pushed
@ S615 turns ON. @ S608 turns ON.
In the REV play mode, the tape Brake solenoid (PM602) is energized.
direction relay (RY601) and solenoid
(PM603) are energized (FWD play
mode)
@® $602 turns ON. ® S610 turns ON.
Pinch roller solenoid (PM601) is
energized,
Reel motors start to rotate.
@® $605 is changed to FF, PLAY @ S614 turns ON.
position. The voltage across B+ voltage for bias osc circuit
brake solenoid (PM602) de- is not supplied yet because
creases. S613 turns OFF.
© S618 turns ON.
If the POWER MAIN switch is
set to AUTO OFF, the machine
turns off automatically at the
end of the tape.
© S620is changed to PLAY position.
® S613 ischanged to PLAY position.
Dummy resistor R611 in B+ circuit B+ voltage is supplied to bias osc
is cut off by S620. circuit.
© S604 is changed to PLAY position. @ S612 is changed to PLAY position.
The voltage across pinch roller
solenoid (PM601) decreases.
(After one second since S604 is
changed to PLAY position (6)).
FF Button Is Pushed
® S611 is changed to FF position. @ $607 turns ON.
FF relay (RY602) is energized
(FF position).
The motor circuit is changed to
supply the rated voltage to each reel
motor.
@® Self-locking contact (1) of FF relay @ Contact (2) of RY602 is closed. @ Contacts (3) and (4) of RY602 are
RY602) i :
( 02) is closed Brake solenoid (PM602) is energized. closed.
Pinch roller solenoid (PM601) is
de-energized.
AC rated voltage is supplied to reel
motors.
@® S602 turns ON. @ $610 turns ON.
Reel motors start to rotate.
These actions @ are not
@® S605 is changed to FF position. @® S614 turns ON.
related to FF operation.
The voltage across brake solenoid
(PM602) decreases.
—12—