Pioneer RT-707 User manual

3-MOTOR 4-HEAD TAPE DECK
RT-707
SERVICE
MANUAL
WMPIONEER

MODEL RT-707 COMES IN TWO VERSIONS DISTINGUISHED AS FOLLOWS:
RT-707
r T >
Type
|
Voltage
Remarks
KU | 120V only U.S.A. model
Kc
120V
only
Canada
mode!
CONTENTS
1.
SPECIFICATIONS
........
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2. CONNECTION DIAGRAM ......... 0. cece cece cece cece eee e eee e ee eeneeeeee 4
3.
FRONT
PANEL
FACILITIES
.......
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5
4.
BLOCK
DIAGRAM
.....
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7
5. LEVEL DIAGRAM .... 0... ccc ete eee e eee eeeeeneeeeees 9
6.
CIRCUIT
DESCRIPTIONS
6:1! “Power Supply ses ccs ean ie eames Shei 2S ends Ae dae oh aaeee oeteasten 10
6.2
Control
Circuit
10
6.3 Direction Switch Circuit .... 2.2... ccc cee eee e eens 13
6.4 Switching Circuit, Muting Circuit... 2.2... 6. cece eee tee eee 14
6.5 Playback Amplifier... 2.2.0.6... cece cece cece eee ee eee eee e eee enee 15
6.6 Bias Oscillator . . 16
6.7. Recording Amplifier 16
6.8
Frequency
Generator
........
6.
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17
7. DISASSEMBLY
TA (BONNE 6.5.5 sci ke Sees ee dace Seis Rea wis We deals Gade aeie sue tek B 21
7.2 Rear Panel .. 21
7.3 Bottom Plate 22
7.4 Front Panel 22
8. PARTS LOCATIONS
8.1
Front
Panel
View
...........
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23
8.2 Front View With Front Panel Removed ............ 00. cece ee cece cece eee 25
8.3. Top View With Bonnet Removed ........ 27
8.4 Bottom View With Bottom Panel Removed 29
8.5) Rear Panel View oieiecc sci6ib aid oboe sia de Relea ele niece 0 a icia eb/6is, aoe valde a wees es 31
9. MECHANICAL ADJUSTMENTS
9.1 Reel Base Height Adjustment ........... 2.0... c cece cece cece cece eeenees 33
9.2: ‘Brake Adjustment: ooo e0.3.3 ic cided cspees cee ees hid eek Sis dee eew eae é 33

10.
11.
12.
13.
14.
9.3. Takeup Torque, Back Tension Adjustment ................. 00: c eee eee 34
9.4
Pinch
Roller
Pressure
Adjustment
35
O15, Pause Adjustments. 24.4 2c.00 25 toed etapa dae ARES eae ayeid weeterd serene ge 36
9.6
Tape
Speed
Adjustment
..............
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36
HEAD ADJUSTMENTS
10.1
Head
Rough
Adjustment
...............-08-
:
vee
37
10.2
Playback
Head
Adjustment
38
10.3
Record
Head
Adjustment
..........0
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38
ELECTRICAL ADJUSTMENTS
11.1.
Playback
Level
Adjustment
2.0.0...
0...
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eneeaes
39
11.2
Playback
Equalizer
Adjustment
39
11.3
Level
Meter
OVU
Adjustment
39
11.4
Dummy
Coil
Adjustment
..........0.
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115
Bias
Trap
Adjustment
......
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11.6
Recording
Bias
Adjustment
.......
40
11.7.
Record/Play
Frequency
Response
41
11.8
Recording
Level
Adjustment
...........0
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EXPEODED
VIEW...
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42
SCHEMATIC DIAGRAMS, P.C. BOARD PATTERNS AND PARTS LIST
13.1. Miscellaneous Parts List .... 2.2.0... e eee e eee ee eee teens 2+. 59
13.2 External Appearance of Transistors, ICs and Circuit Diagrams of IC 60
13.3 Connection Diagram .... 2.0... . cece ce cee eee eee cence nee eeeneenes 61
13.4
Schematic
Diagram
.......
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13.5
Playback
Amplifier
Assembly
(RWF-069)
..........
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65
13.6
Meter
Amplifier
Assembly
(RWX-155).......
71
13.7.
Power
and
Oscillation
Assembly
(RWR-053)
73
13.8
Indicator
Assembly
(RWX-142)
......
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13.9 Fuse Assembly (RWX-141) ....
13.10
Equalizer
Amplifier
Assembly
(RWX-154)
13.11
Head
Amplifier
Assembly
(RWF-070)
...........
0.0
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13.12
Connector
Assembly
L
(RWX-151)
22...
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13.13
Connector
Assembly
R
(RWX-152)
.........
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13.14
Function
Switch
Assembly
(RWS-052)
..........
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13.15
MIC
Amplifier
Assembly
(RWF-065)
..........
0...
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13.16
Control
Assembly
(RWG-070)
.......
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13.17
Servo
Amplifier
Assembly
(RWG-076)
.......
13.18
Switch
Assembly
(RWS-058....
.
KC
type)
(RWS-059.....
KU
type)
PACKING)
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106

1. SPECIFICATIONS
Type acchanes op Bass 4-track, 2-channel stereo tape deck
(Recording, playback with reverse
playback)
. Solenoid drive, Pushbutton direct
change system, Timer can be set for
recording and playback.
HeadSis asters toate e Recording Head ; 1
Erase Heads ; 1
Forward playback Head ; 1
Reverse playback Heai
Motors... 02.22.0005 Capstan drive moto
(FG-system, AC servo, direct drive)
Reel base drive motors ; 2
(6-pole inner rotor induction type)
Acceptable Reel Size . Tin (17m)
Tape Speed 19cm/s (7-1/2ips), 9.Scm/s (3-3/4ips)
40.5%
Less than 100 sec. with 7-inch
reel and 370m tape
Wow and Flutter... .. . . Less than 0.05% WRMS (19cm/s)
Less
than
0.08%
WRMS
(9.5cm/s)
More than 58dB
Fast Forward/Rewind Times ... .
Signal-to-Noise Ratio.
Total
Harmonic
Distortion...
..
.
Less
than
1%
(19cm/s)
Frequency
Response
i
eee
eerie
weir
20Hz
to
28,000Hz
(30Hz
to
24,000Hz
+3dB)
SSM:
5 kis
toast
20Hz
to
20,000Hz
(30Hz
to
16,000Hz
+34B)
ome
More
than
S0dB
Channel
Separation.
.
More
than
S0dB
Erasure
Rate
.
More
than
704B
Recording
Bias
Frequency
.
.
125kHz
Equalization.
.........
NAB
Standards
Inputs
(Sensitivity/Maximum
allowable
level/Input
impedance)
MIC;
0.25mV/125mV/27k2,
6mm
diam.
jacks
(suitable
microphone,
2502
to
30k22)
LINE;
50mV/25V/100k2,
DIN;
16mV/8V/1.3k22,
DIN
standards
Outputs
(Reference
level/Maximum
level/Load
impedance)
LINE;
450mV/700mV/SOk2,
DIN;
450mV,
700mV/50k2,
DIN
standards
HEADPHONES;
70mV/822,
6mm
diam.
jack
Semiconductors.
. .
+
67
transistors
(4
FET’s),
5
IC’s,
47
diodes
(1
thyristor,
2
LED's,
4
Zener
diodes,
2
varistors,
)
Crosstalk
Accessory Functions
©
Pitch
control
(more
than
+6%
of
rated
tape
speed)
@ Auto reverse playback (with sensing tape: manual reverse is
possible)
© Auto repeat (counter-interlocked)
© Recording mode switches (L, R independent)
© Tape selectors: BIAS (STD/LH); EQ (STD/LH)
© MIC/LINE mixing
© Output volume controls
‘© Pause indicator lamp
Power Requirements... . . AC 120V 60Hz
Power Consumption . 120 watts, Max.
AC Outlets,
Dimensions . . . .
. » Unswitched (300W max.) x 1
+ 480(W) x 230(H) x 356(D)mm
18-29/32 x 9-1/16 x 14in
Weight... 22.2.0 000- Without package; 20.0kg 441b loz
With package; 23.5kg 511b 1302
RT-707
Accessories .......... © Tin metal reel (Pioneer PR-85) x 1
Connecting cord with pin plugsx2
Head cleaning kit x 1
Sensing tape x 1
Splicing tape x 1
Operating instructions x 1
NOTE:
Specifications and the design subject to possible modification
without notice due to improvements.

2. CONNECTION DIAGRAM
LINE
output level
controls
I
|
SS
DQUOQUNAON000 00)
QQQA0UI0N00U0U1
Ac OUTLET
MAX MIN
OUTPUT LEVEL
AC OUTLET
This is the power socket (maxi-
mum power capacity: 300W).
You can connect the power plug
on another tape deck or amplifier
to this socket,
These controls can be used to
adjust the LINE output levels.
Turn them clockwise to increase
the levels, They have a center
click position where the standard
output level (450mV with 0dB
displayed on the level meter) of a
standard tape can be obtained.
terminal
To the power
outlet or AC
outlet on the
stereo amplifier
Ground wire
Tape connectors of
RT-707's playback /
the stereo amplifier
recording connectors
TAPE
OUTPUT
INPUT
Connections for
recording a
mol
|
IN/OUT
Left channel
DIN connector
Connections
for
playback
Right
channel
Left channel
REC/PLAY connector
(DIN
standard)
of
sec-
‘ond stereo amplifier
REC/PLAY
001006
¢@670090
Recording/
playback
cord (DIN
standard)

3. FRONT PANEL FACILITIES
POWER SWITCH
Push this switch and power is supplied to the tape deck. Push for a
second time to turn the power off.
SPEED SWITCH -
This switch selects the tape speed. Push for a 9.5cm/s speed; push
again for a 19cm/s speed (released position).
19cm/s: Used for recording music programs, etc.
9,5cm/s: Used for recording lengthy conversations, etc.
PAUSE LAMP:
This green lamp lights up when the PAUSE button is pressed to
indicate the tape has stopped temporarily.
PHONES JACK
This is the output jack for stereo headphones. Signals selected by
the MONITOR switch are available here. Use it when you want to
monitor the recording or listen to a performance directly taped
from the RT-707. The output level is not variable.
MIC JACKS €)
These
are
the
input
jacks
for
microphone
recording.
The
L
(left)
and
R
(right)
channels
can
be
used
independently.
Only
the
micro-
phones’
input
signals
are
recorded
if
the
REC/PLAY
connector
(DIN
specifications)
on
the
rear
panel
and
the
MIC
jacks
are
connected
at
the
same
time,
As
long
as
the
microphones
have
a
standard
6mm
diameter
plug,
you
can
use
either
a
low
impedance
(600-ohms)
or high impedance
(10 — SOkohms)
type.
MIC
RECORDING
LEVEL
CONTROLS
Use
these
controls
to
adjust
the
recording
level
when
you
are
recording
with
a
microphone
(or
microphones)
or
when
you
are
using the rear panel REC/PLAY
comnector
(DIN standard).
Use
the
outer
control
for
the
right
and
the
inner
control
for
the
left
channel.
Input
signals
from
both
the
MIC
jacks
and
the
REC/PLAY
connector
cannot
be
recorded
simultaneously.
LINE RECORDING LEVEL CONTROLS
Adjust the recording input level from the LINE INPUT terminals
‘on the rear panel. The level increases as the controls are turned to
the
right.
The
outer
control
is
for the
right
channel
and
the
inner,
for the left.
RECORDING LAMP (REC)
This red lamp lights up during recording. Check that it has lit up
before recording.
MONITOR SWITCH
Use this switch to monitor your recording.
TAPE: Allows you to listen to the recorded signals.
SOURCE: You can listen to the signals before recording if this
position is selected (press switch once).
If this switch is switched alternately to SOURCE and TAPE during
recording, you can compare the sound signals beforé and after
recording.
BIAS SWITCH
This
selects
the
recording
bias
current
according
to
the
type
of
tape
used
for
recording.
Push
for
LH
tapes;
push
again
for
STD
tapes (released position).
STD:
For
standard
tapes.
LH:
For
low
noise
and
high
output
tapes.
EQ SWITCH
This
selects
the
recording
equalization
characteristics
according
to
the
type
of
tape
used.
Select
same
position
for
playback
as
for
recording
according
to
the
characteristics
of
the
recording
tape.
Push for LH; push again for STD (released).
STD: For standard tapes.
1H: — For low noise and high output tapes.
TAPE COUNTER
This indicates how much tape has been recorded or played back
and how much there is left over.
REPEAT BUTTON
This button allows you to reverse the tape forward for reverse
playback automatically. If you remember to worrk the tape
counter and REPEAT button, then the tape will automatically be
reversed and the tape deck will be set to forward playback when
the “0000” display on the tape counter gives way to "9999"
during reverse playback. Be sure to release this button when you
do not require repeated playback.
COUNTER RESET BUTTON
Push this button to reset the tape counter to “0000"
LEVEL METERS
These allow you to read out the levels during recording and play-
back. When the MONITOR switch is set to SOURCE, they
indicate the input signal level, and when set to TAPE, they
indicate the playback output level.
APSTAN
This rotates when the power is switched on, Together with the
pinch roller, it keeps the tape at its rated speed.
PITCH CONTROL KNOB
You can use this to make the tape travel 6% faster or slower than
the normal tape speed during playback. When set to the central
position, the tape speed is 19cm/s or 9.5cm/s (standard values).
Turn the control to the left and the speed drops and the musical
steps are lowered; conversely, turn it to the right, and the speed
rises and the musical steps are raised. This control cannot be used
during recording.
RT-707
REC MODE SWITCHES (L. R)
Depress
these
switches
when
recording.
L: Use this switch for L (left) channel recording.
R: Use this switch for R (right) channel recording.
For stereo recording, make sure that you depress both switches.
7 TAPE DIRECTION SELECTOR BUTTONS
These buttons allow you to select the direction of tape play during
playback. When depressed, the button’s lamp will light up to
indicate the direction of tape play.
Forward playback: The tape runs from left to right.
Reverse playback: The tape runs from right to left.
When you are recording, you cannot change the direction of tape
play even by depressing this button. The tape will always run ina
forward direction.
PAUSE BUTTON
This
temporarily
stops
the
tape
during
tape
play.
When
pressed
during
recording
or
playback,
the
tape
merely
stops.
When
pressed
again,
the
tape
starts
to
run.
This
button
does
not
work
during
fast forward or rewind.
FUNCTION BUTTONS
44 REWIND: This cause the tape to be wound at a high speed
from the right to the left reel.
>P FAST FORWARD: This causes the tape to be wound at a
high speed from the left to the right reel.
PLAY: For tape playback, or recording, push this button.
REC: To record, press this button together with the PLAY
button.
@™ STOP: This stops the tape and releases the other function
buttons.
NOTE:
© The function buttons will not return to their preset positions
if the power is turned off.
© The tape will always run in a forward direction when the
POWER switch is depressed to the ON position.
© If you depress both the PLAY and REC buttons with the
tape set to the reverse playback direction, then the tape will
sometimes move slightly backwards and then start to run
forwards. Therefore, when recording, make sure that you set
the DIRECTION button to the forward playback position.
© There is no need to press the (j™) stop button if you want
to change over from one function to another.

4. BLOCK DIAGRAM
HEADPHONE Amp.
METER DRIVE Amp.
PB. HEAD >
(FWwO)
NOTE:
The
number
which
are
circled
in
the
block
diagram
indicated
the
points
which
are
to
be
measured
in
the
level
diagram.
@
HEAD
PHONES
ca
LINE OUTPUT
o]
MIC INPUT
DIN
LINE
INPUT
i
©
CONTROL Ass'y
INDICATOR
a
ig
5
Ped
0
|
|
Su
Si2|
gp.
ac
‘“
Su-3
a
s
baa
io Sto q™ Seg
foe ee
AC 120V
CF sO Hz
SWITCHES
St
Se
S3
Sa
Se
St
Se
Sa
Sis
Se:
: POWER
: SPEED
+ MONITOR
= BIAS
Ss:
E.G
RECORD LEFT
» RECORD RIGHT
: REW
: FWD
Sto =
Sit
Sr:
Sa:
Su:
PLAY
REC
PAUSE
Fwo
REVERSE
REPEAT
SHUT OFF
RELAIES
RY301 :
RY202 :
RY en
RY
oz
:
LAMPS
Pu
Plz:
Pla:
Pla:
REC LEFT
REC RIGHT
:
PLAY
DIRECTION
: LEVEL METER LEFT
LEVEL METER RIGHT
FwD INDICATOR
REVERSE \NDICATOR

RT-707
5. LEVEL DIAGRAM
NOTES:
OdBu=1V
Frequency: 1kHz
(PLAYBACK)
The
level
measurement
points
are
indicated
on
the
block
diagram.
dBy
a4
©
vaby
©
-7aBv
@-1468v
-2074
LEVEL
- 60
(RECORDING }
©-10aBv
-20dBv
20
(© -3048
-30
@
}OdBv
@-a1aBv
-40
® -46dBv
LEVEL
~90

6. CIRCUIT DESCRIPTIONS
The block diagram is shown on page 7.
Model RT-707 is an open reel tape deck charac-
terized by direct drive 4-track 2-channel configu-
ration, 3 motors, 4 heads autoreverse
The sensor touch pushbuttons used in most 3-
motor tape decks necessitate a relatively large num-
ber Of relays in the transport control electronics;
the RT-707, however, uses locking type pushbut-
tons which permit simplified circuit construction
and also facilitate automatic unattended recording
in conjunction with a timer.
6.1 POWER SUPPLY
When the power switch S, is switched on, AC100V
is supplied to the capstan motor from the secon-
dary side of the power transformer, and the motor
begins to rotate. A DC voltage rectified in Dgo,
D4o2, stabilized in the stabilizer formed by Q4o1,
Q4o2 and ZD4o,, is supplied to the control circuit
(Fig. 1).
6.2 CONTROL CIRCUIT
The control circuit is shown in Fig. 2. Table 1
indicates the transistor states for the different
transport modes.
@ Play Function (Fig. 2)
1.
When
the
play
button
S,0-,
is
pushed,
ground
connection
of
R497
is interrupted
and
the
base
circuit
of
Q4o,
is opened.
No
current
can
flow
through
Q4o4,
and
it enters
OFF
state.
2.
+B
voltage
causes
current
to
flow
along
the
route
Daos > Qaog > R413 > Raio,
whereby
Qao5
is turned
ON.
3.
As
R47
is
connected
between
base
and
emitter
of
Qos,
this
transistor
is
turned
ON.
The
collector
current
of
Qu4o9
activates
brake
solenoid
SL,,
pinch
solenoid
SL,
and
play
relay
RY...
4.
+B
current
also
flows
along
path
Dao;
>
Qyos
>
Rai
>Raio,
whereby
Q4o;
becomes
ON.
5.
As
Rais
is
connected
between
base
and
emitter
of
Q4i0
,
base
current
can
flow
and
the
tran-
sistor
becomes
ON.
Q4io
collector
current
activates
PAUSE
solenoid
SL;.
Operation
of
brake
solenoid
SL,
releases
the
brakes
of
the
supply
motor
(SM)
and
take-up
motor
(TM).
Operation
of
the
pinch
solenoid
SL,
causes
the
pinch
roller
ta
be
pressed
against
the
capstan.
Operation
of
the
play
relay
RY¢o;
enables
AC
70V
from
the
secondary
side
of
the
power
transformer
(see
Fig.
1)
to
be
applied
to
the
supply
and
take-up
motors
through
slide
resistors
R,
and
R;.
Power
switch
}
Si
|
ACI20V -~ ?
60Hz
;
a
Ry6o1-2 ~ a
10
Fig. 1

@ Rewind (& Fast Forward) Function (Fig. 2)
1.
When the rewind button S3_-; is pushed, +B cur-
rent flows along the path brake solenoid SL, >
Dao7 > Ss-3, and SL, operates, releasing the
supply and take-up reel brakes.
As shown in Fig. 1, AC100V is applied to the
supply motor via F.F. button S,., and Rewind
button S,-, , and tape rewind begins.
. AC100V also flows to the take-up motor via
F.F. button S,., > rewind button S,., > slide
resistor R, > play relay RY¢o, . The slide resis-
tor serves to apply the proper amount of back
tension to the take-up motor in rewind mode.
. In F.F. mode, on the other hand, AC100V
from the secondary side of the power trans-
former is applied to the take-up motor through
F.F. button So.,.
AC100V also flows to the supply motor via
the route formed by S,.; > play relay RY¢o: >
slide resistor R,. The slide resistor serves to
apply the proper amount of back tension to
the supply motor in fast forward mode.
RT-707
© Solenoid Voltage Control Circuit (Fig. 2)
When transport functions are switched, operating
current of the solenoids must be temporarily in-
creased to effect the switching action, but current
must be reduced again immediately to avoid over-
heating of the solenoids.
1. When, for example, the play button is pushed,
a surge of charge current (base current from
Q407) flows to Caog, and Qao7 is turned ON.
2. Brake solenoid SL,, pinch solenoid SL,, play
relay RY go, and pause solenoid SL; are con-
nected as loads to Q4o3. As explained under
PLAY FUNCTION, above, these solenoids
operate in play mode, whereby the Q4o7 emit-
ter current becomes the Q4os base current,
turning Q4o3 ON.
8. As soon as C4og has been charged, bias of Qso7
returns to the normal operating value deter-
mined by stabilization in Rais;, ZDao2-
Table 1
| Transport Mode Transistors in ON state Transistors in OFF state
| STOP Q4o4 Q403, Q405+ Qa06, Qa09s Qaro
PLAY Q403, Qaos, Qa06, Q409, Qaio_| Qaoa
FF/REW Qaos Q4031 Q4051 Qa06 Qao9» Qaio
PAUSE Qaos; Qaos, Qaoss Qsi0 Qsoa, Qso9
Capstan Motor
Solenoid
use Solencid
Sle : Pir
RY¢o1: Play Relay
59.3 510-2 cal t
Fig. 2
44

@ Time Lag In Switching Functions (Fig. 2)
When the transport is switched from rewind (or
fast forward) directly to play mode, it is necessary
in the interest of tape protection to bring the tape
to a standstill for a certain length of time.
Switchover from fast forward or rewind to play
1. In F.F. (or rewind) mode, Q4o, base current
flows via the route formed by Rao9 > Qaoa >
R4o7 > play button Syo-2, and Quaog is in ON
state.
2. Therefore (and because the Qao3 base is con-
nected to the Qyoq collector via R4os), reverse
bias is applied and Qgo3 is OFF.
8. +B voltage causes a current flow through R4o3
> Caos > Raos > Daoa, whereby Caos (timing
capacitor) is charged.
4. When the Play button is pushed, the F.F.
switch S53 is turned off, and C4, begins to
discharge via D4o3 > Raoo > Qaoa > Raoo- AS
Qsoa base current gradually decreases, its
internal resistance goes up and Q4oq attains
OFF state.
5. When Qaoa becomes OFF, Qyos, Qao6, Qaog and
Qsio become ON (as explained under PLAY
FUNCTION, above).
6. Therefore, the brake solenoid SL, , pinch sole-
noid SL,, play relay RY¢o; and Q4i9, operate
and the unit enters play mode.
7. The required stop time between pushing of the
play button and start of play is determined by
the discharge time of Cao¢; it is approximately
2 seconds.
@ Pause Function (Fig. 2)
1. When the pause button S,. is pushed while
the transport is in play or rec mode, potential
at the base of Qyoo becomes OV, meaning
that Qao9 becomes OFF.
2. Thereby the loads on Q4o9, i.e. brake solenoid
SL, and pinch solenoid SL, are released; sup-
ply and take-up motor brakes are applied and
the pinch roller retracted from the capstan.
3. Play relay RY¢o; also opens, and AC7OV cur-
rent flow to the take-up and supply motors is
interrupted. The motors stop, the transport is
new in pause mode.
4. The pause indicator LED also lights.
5. When pause switch S,, is released, current again
flows through the base of Qyoo, the transistor
becomes ON, brake solenoid SL, , pinch sole-
noid SL,, play relay RY,o; and pause solenoid
12
SL; operate, and play or rec mode is resumed.
Refer to PLAY FUNCTION, below.
NOTE:
With the pause switch S,, on, Q,,. remains on, and +B
voltage is still applied to pause solenoid SL,. The pinch
roller is therefore retracted only about 2mm from the
capstan.
@ Record Function (Fig. 3)
1. The unit is put into recording mode when the
play (Sio-2) and rec (S,,-3) buttons are oper-
ated at the same time.
2. +B current flow is as follows; rec button S,,-;
> play button Syo-; > F.F. button Sy. >
REW button S,., ~ recording switch S,(S;) >
D2 (D703) > speed switch S,., > bias switch
S, > OSC assembly. Current is also supplied to
the rec indicator LED, Dgo,-
3.
Output
from
the
bias
oscillator
is
supplied
to
the
recording
and
erase
heads.
4.
At
the
same
time,
recording
signal
current
(which
is
grounded
through
rec
relays
RY30o:
and
RY%3o2
in
other
modes)
is
supplied
to
the
recording
head
to
be
recorded
on
tape.
Relay
correspondences:
R3o;
left
channel,
R302
right
channel.
NOTES:
@
Functions
of
the
control
circuit
in
rec
mode
are
the
same
as
in
play
mode.
@
The
above
explanations
of
rec
functions
refer
to
stereo
recordings.

REW OFF PLAY = REC.
ofr S82 See 9 Stor St
t
RT-707
= REC Relay L Se: REC Left
: REC Relay R $7: REC Right
Spee Laos, Looe : Dummy Coil
Bias Den: REC IND. Lamp
ON
6.3 DIRECTION SWITCH CIRCUIT
Fig. 4 shows the direction switch circuit diagram.
@
Forward
Play
1.
When the power switch S, is turned on, current
caused by +B flows along the route formed by
reversing relay RYoo, (and forward indicator
lamp PL;) > direction change relay RY¢o1-2 >
ground.
Relay RYoo, thus operates, causing the capstan
motor to rotate in forward direction, and
lighting the forward indicator lamp in the FWD
direction button.
. If now the play button is pushed, forward
play will begin.
@
Reverse
Play
1.
When the direction change switch S,, is de-
pressed, +B will flow along the following path:
rec button S,;-3 > Reo: + direction change
relay RY¢o2 > direction change switch S,4 >
ground.
The direction change relay RY¢o2 operates,
changing its contact points for reverse direc-
tion.
This interrupts the current through the revers-
ing relay RY, (and FWD indicator lamp).
Due to the contact points in relay RYo1,
polarity in the main motor coil is reversed, and
the capstan motor begins to rotate in the
reverse direction. The REV indicator lamp
lights.
Fig. 3
@ Auto Reverse Function
1;
Automatic
reversing
of
the
tape
travel
direc-
tion
can
be
effected
by
attaching
a length
of
conductive
sensing
tape
near
the
tape
end.
As
the
sensing
switch
is
short-circuited
by
the
sensing
tape,
a current
path
is formed
for
+B:
rec
button
S,;-3
>
Reo;
>
direction
change
relay
RY¢o2
>
play
button
Sjo-.
>
sensing
switch
>
ground.
Thereby,
tape
travel direc-
tion
is
reversed,
because
the
direction
change
relay
RY
602
operates.
@ Repeat Function
i.
When
the
repeat
button
S,,
is
engaged
and
the
tape
counter
reset
to
0000,
the
unit
is
ready
for
automatic
repeat
function.
First
play
the
tape
in normal
forward
direction.
.
Sensing
tape
will
cause
automatic
reverse
in
travel direction (as explained above).
.
As
the
tape
reverses
past
the
0000
position
of
the counter and the counter returns to 9999,
the tape counter switch is activated.
.
Action
of
the
tape
counter
switch
short-circuits
the direction change relay RY¢o2, the relay’s
contact points are opened, and forward play
resumes.
The unit will thus repeat playing the section
between 0000 and sensing tape indefinitely.
NOTE:
Automatic
resumption
of
forward
play
at
counter
reading
9999
will
also
take
place
if
the
unit
has
been
switched
to
reverse
play
manually,
i.e.
without
sensing
tape.
13

RY602 : Direction Relay
RYs0! : REV Relay
PL3 : FWD IND. Lamp
PLa
=
REV
IND.
Lamp
6.4 SWITCHING CIRCUIT, MUTING CIRCUIT
Fig. 5 shows the switching circuit for forward play/
reverse play switchover, as well as the muting cir-
cuits operative during switchover and when the
power to the unit is first turned on.
© Forward Play/Reverse Play Switching Circuit
1. +B flows along the route REV indicator lamp
PL4 > Ruiz > Rior * Qior > Rios > Ground.
Qio: is in ON state, and the output from
IC, 19, enters the subsequent amplifier stage.
2. The base of Qio3 is grounded through Rio >
Rin > direction change relay RY¢o2-2 >
ground, so Qio3 is off and the output from
IC;192 cannot enter the subsequent amplifier.
The signals from the playback heads are thus con-
stantly amplified in head amps IC,;o; and ICj102,
respectively, but the signals paths are switched by
Q101+ Qio2 in accordance with tape travel direction.
© Muting at Time of Tape Travel Direction Change
A muting circuit interrupts amplifier output during
the time that the tape reversing its direction of
travel, is not moving at the rated speed of 19 or
9.5cm/s.
1. During forward play, C,.; remains discharged
through route R,,, > direction change relay
RYoo2-1 > Risa > Dios > ground.
2. When the travel direction is changed from
forward to reverse play, +B causes a charging
current to flow to C,,; through forward indi-
cator lamp PL3 > Ry > Ci2s + Dio2 > Riss >
Qiiz- Quiz is ON, while Qi15 is OFF.
3. Consequently, the voltage drop across Ri6
(which is the load on Q;,s) becomes small.
The positive potential at the Qio; base (from
14
a. SENSING SW
a
”.
NOTE:
The reversing relay RYo, is located
inside the capstan motor assembly. Fig. 4
R,;;) is cancelled out, the base obtains positive
potential, and Qo; becomes ON. By reducing
the impedance between collector and emitter,
the output from the IC’s is muted.
4. When C,.; has been fully charged, Q,,7 base
current stops flowing. Voltage drop across
Riso, the load on Q;;5, becomes large, the base
of Qios obtains negative potential from Rj\5.
This increases the collector-emitter impedance
of Qios, and no muting of the IC outputs
takes place.
© Muting at Time of Power Switch-on
1.
When
the
power
is
switched
on,
current
flows
along
the route
+B (25V)
+ Dios > Quis >
Ries - A voltage
appears
across
Rj65 .
2. This voltage across Ris; is applied to Qii3
through R35, whereby Q,,3’s collector-emitter
impedance drops and muting of the line out
signal is effected.
3.
Through
+B
(25V)
>
Ciro
>
Riso
>
Quis,
a
charging
current
flows
to C,,9,
resulting
in a
drop
in Qj;
collector-emitter
impedance.
This means
that muting
by Q,,; is dependent
upon the C,;9 and C,,; charging
currents.
Cy19
serves
for brief muting
while the power
is being
switched
on, whereas
C,,,; causes
approx.
3
seconds
of muting
after switch-on.
4. When C,,5, C2; have been charged, a negative
potential builds up through Riaz > Riso >
Qii3, resulting in an impedance drop between
Qii3 collector and emitter and thus ending the
period of muting.

tenor
MONITOR,
Tape Qer, Qios
RT-707
——— Lo out
—{— AMP. Ass'y (+8)
6.5 PLAYBACK AMPLIFIER (Fig. 6)
1. The playback signal from the playback head
enters IC, ,o; through C,y93.
The amplified output from IC,,9, undergoes
playback equalization in the equalizer formed
by VRio1, Riso9, Riso7, Cris.
. The difference in equalization between 19cm
and 9.5cm/s tape speeds is obtained by varying
the voltage applied to the gate of FET Qiio
(0.4V for 19cm/s, -8.5V for 9.5cm/s) and
utilizing the resultant change in the FET’s
internal impedance.
. Downstream from ICj1o1, the signal path is
switched by Qo, whose function has been
2.
CONTROL
Assy
(+8)
(-B) POWER
Fig, 5
explained
under
7.4,
Switching
Circuit,
Muting
Circuit,
above.
The
signal
is
then
amplified
in
the
direct
coupled
NPN-PNP
amplifier
(Qio7,
Qio9)
and
becomes
available
at the line output
terminals.
.
A
portion
of
the
output
signal
undergoes
im-
pedance
conversion
in
Q,,,
and
matching
trans-
former
T,o;
and becomes
available
at the
phones
output
jack.
.
For
driving
the
level
meters,
output
from
Q,1;
is
amplified
in
Qjo9,
and
rectified
in
Djoo.,
Dyoos-
TAPE
ee
=
Fig. 6
15

6.6 BIAS OSCILLATOR (Fig. 7)
1.
16
Se-2
‘30s
L906
Sr2
REC.
HEAD
L
When +B (approx. 30V) is applied to Qs3o;,
Q30s, & positive feedback loop is established
through the oscillator transformer T3.:, and
oscillation begins.
. From the secondary side of TR3o,, the oscilla-
tion signal is supplied to the erase and record-
ing heads.
. The oscillation frequency is stabilized against
temperature fluctuations by means of thermis-
tor TH39, which regulates the base current of
Q30s , Qs06 g
. In monaural recording, the REC (L) switch
S.-2 or REC (R) switch S,_,, respectively, is
switched to a dummy coil which maintains
uniform load on the oscillator, for stable opera-
tion.
( aeeaat
: 2 ”
1
1)
i
6
6.7 RECORDING AMPLIFIER (Fig. 8)
.
Input
from
the
microphone
jacks
passes
through
Co, and is amplified
in the 2-stage
direct
coupled
amplifier
formed
by Qzo1,
Qro3 -
. Output from this mic head amp, after level
adjustment by VR2,, enters Qro5 -
Line input is level adjusted in VR203 and then
enters Q2o;. Mic and line inputs can thus be
mixed, with independent level adjustments
for each.
.
The
signal,
amplified
in
Q29s,
Q207
passes
through
VRjo2
and enters
the base of Q3;.
- Q301 and Q3o3 serve to obtain the current
required for driving the recording head.
A feedback loop (Q303 collector > R313, C307
> Rsis > Qso1 emitter has been provided to
obtain
+4dB
at
20Hz
of
bass
equalization.
.
To
achieve
the
different
amounts
of
treble
equalization
required
for the two tape speeds,
a transistorized
switching
circuit
has been
included.
Assuming, for instance, that low noise high
output tape is being used at 19cm/s: a positive
voltage is applied to the base of Q3o7, its
internal impedance drops, and the series
resonant circuit constituted by L3o,:, Csi3,
functions.
-
From
Q3o3,
the
signal
enters
the
recording
head via L393, C325.
L393 and C325 are tuned
to
the recording
bias
frequency,
reverse
bias flow in the circuit.
preventing
19cm/s 9. 5em/s
Fig. 8

6.8 FREQUENCY GENERATOR
The frequency servo generator block diagram is
given in Fig. 9. For the circuit schematic, please
refer to page 95.
One-shot Multivibrator _
Integration Circuit
—
ary
aes
| as sd
Limiter Amp
Differentiation Circuit
The construction of the frequency generator
(abbreviated FG) is shown in Fig. 11.-The rotor
is mounted to the flywheel and the stator, magnet
and generation coil are installed to the motor
bracket.
The magnetic flux from the magnet flows through
the loop stator teeth ~ rotor teeth ~ magnet. When
the motor rotates 1 revolution, the rotor and
stator teeth alignment changes as illustrated by a
and b of Fig. 10. Therefore, the amount of magnet-
ic flux (magnetic flux density) flowing through the
loop changes. An AC voltage of a frequency pro-
portional to the number of times the magnetic
flux density changes is generated in the genera-
tion
coil.
The
output
signal
of
this
FG
is
appro-
ximately 1360Hz, 150mV at a tape speed of
19cm/s.
Rotor teeth
Stator teeth
Rotor teeth
Stator teeth Fig. 10
Brake Circuit
RT-707
'
| Q
91
: 1
i
Stator Generation coil
Magnet Stator
Fig. 11
17

@ Limiter Amplifier and Differentiator Circuit
The limiter amplifier and differentiator circuit are
shown in Fig. 12. The AC signal generated by the
FG circuit is shaped to the square wave shown in
Fig. 17-2 (Fig. 12-a) by an IC limiter amplifier.
The output of this amplifier is shaped into a pulse
by
a
CR
differentiator
circuit
and
the
positive
pulse of Fig. 17-4 (Fig. 12-b) is extracted by means
of a diode D,
(a)
t 7 (b)
C OUtPUt 05)
C Do
bf pig
eT
@ One-shot Multivibrator Circuit and Integrating
Circuit (Fig. 13)
The positive pulse obtained above is used to trigger
a one-shot multivibrator. When there is no input
signal, Qoo, is OFF and Qoos is ON and point
becomes
nearly
stable
due
to
the
voltage
drop
across Ry,. However, when a positive pulse is ap-
plied to the input of the multivibrator, Qoos is
turned ON, Qoos is turned OFF (Q, collector cur-
rent
doesn’t
flow)
and
the
voltage
of
point
@
rises to near the power supply voltage. The multi-
vibrator remains in this state during time T, deter-
mined
by
the
time
constant
of
C
and
R
and
then
returns to its original stable state.
In short, positive square waves equal to the number
of input trigger pulses are produced. When the
frequency
of
the
signal
generated
by
the
FG
circuit
changes
(motor
speed
changes),
the
spacing
T;
of
the
trigger
pulses
also
changes.
Looking
at
this
at
point
@),
the
output
is
different
for
the
time
interval
of
T,,
output
OV
as
shown
in
Fig.
17-5.
If the output of a one-shot multivibrator is passed
through an integrating circuit consisting of Rx and
Cx, when the closing time of T, is long as illus-
trated in Fig. 17-6, the output of point B at which
the DC has changed can be made low and the
change of T, (change in speed) can be extracted as
a DC voltage change. Moreover, the speed (tape
speed) may also be changed even when T, is
changed in a like manner. In this machine, the tape
speed is adjusted by changing R.
Fig. 12
18
Trigger pulse input
"Fig, 13
© Differential Amplifier
The DC voltage ADC obtained at the low-pass filter
circuit is applied to the differential amplifier of
Fig. 14 and compared with the reference voltage.
The difference between this voltage and the DC
voltage obtained at the correct speed, that is, the
voltage component produced by the speed error,
is operated differentially.
For instance, when the motor speed is too fast,
since ADC increases, Ig, increases, the voltage of
point A rises, Ig, decreases, and AEo also de-
creases. This AEo is sent to the drive circuit.
Reference voltage
Fig. 14
©
Drive
Circuit
The drive circuit is shown in Fig. 15.
Eo of the differential amplifier is the input of
Qoog. When AEo is reduced (that is, when the speed
of the motor is fast), the collector current of Qoos,
Qoog and Qojo is reduced until, finally, the internal
resistance of Qoo; increases.
When point @) has become positive, the current
path from the AC input is through the route A >
motor
winding
>
Dooi-2
+
Qs01
>
Door-3
>
®B)
and
when point (B has become positive it is through
the route (B) > Dooi1 + Qo01 > Doora > motor
winding > @). The increase in the internal resist-
ance of Qo; causes the motor current winding cur-
rent to decrease and the motor speed decreases and
is returned to an accurate speed.

+B
© Brake Circuit
The brake circuit is shown in Fig. 16. Input EA of
Qo is the collector output of the differential am-
plifier Qoo7 (Fig. 14). Voltage Ep of point a is set
by RA, RB so that it is higher than Eg at the rated
speed. Consequently, Qoi1, Qoi2 and the SCR are
turned OFF and the brake is not operated.
If it is assumed that the tape speed has been
switched from 19cm/s to 9.5cm/s, for example,
the servo circuit detects the change in speed. The
internal resistance of Qoo; of Fig. 15 increases, the
motor winding current decreases and the motor
speed decreases. Since the motor is unloaded if the
function switch on the tape deck is set to a posi-
tion other than PLAY (REC) at this time, it is
rotated by the inertial energy of the flywheel and
the rated speed is not reached immediately (this
machine requires about 10 seconds to reach the
@
AC input / \
©
Fig. 15
rated
speed).
The
increase
of
EA
when
the
speed
has
deviated
to
the
high
side
as
described
in
the
“Differential
amplifier’
section
is
utilized
to
im-
prove
on
this.
When
EA
>
Ep,
Qon,
Qo12
and
SCR
are turned
ON, DC (pulsating)
flows
in the motor
winding
and
the
magnetic
brake
is
applied
to
the
motor
and
the
time
required
for
the
motor
to
drop
to the rated speed
is shortened.
The
brake
current
flows
through
the
following
route:
When
point
@
of
the
AC
input
has
become
posi-
tive:
@
>
motor
main
coil
>
motor
auxiliary
coil
> Re > SCR > Doo-s
>B
When point (®) has become positive, the SCR acts
as
a
diode
and
reverse
current
doesn’t
flow
and
brake current doesn’t flow.
AC input
19

Frequency too low
(Rotation too slow)
Fig. 17-1 FG Output
Fig.
17-2
Limiter
Output
Fig. 17-3 Differentiator Output
Fig.
17-4
Trigger
Input
T3
——4
Fig. 17-5 One-shot Multivibrator Output
T T
1 Te 1
Fig.
17-6
Integrator
Output
Too low
Frequency too high
(Rotation too fast)
T3 —4
jo
Te’
4
T
Te!
Too high
RT-707
Fig. 17
20

7. DISASSEMBLY
7.1 BONNET
Remove the screws 1 ~ 8 on the each side
of the bonnet, then remove the screws 9 ~
10 as shown in Fig. 18.
Fig. 18
7.2 REAR PANEL
Remove the screws 1 ~ 9 to detach the rear
panel, then remove the screw 10 for ground as
shown in Fig. 19.
Fig. 19
21