Pioneer RT-707 - 6. Circuit Descriptions; Power Supply Circuit; Control Circuit Operation

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