Marantz SD9000 - Page 11

. The PLAY signal level in the output of the micro-
computer rises to ‘’H” (this signal turns on 0529 and
Q527 through a circuit via a separate route). (Fig. 3-1)
. The PLAY = signal is differentiated, then passes
through Q569 and turns ON Q534 momentarily.
Ras 0533 is OFF when 0534 is ON.
So c. When 0533 is OFF, a bias voltage of about 22V is
- applied to the base of Q532 through Zener diode
Q562. At this time, the output of the emitter of
0432 is about 20V.
Since Q529 and 0527 are ON, a voltage of 20V is
applied to the PLAY solenoid L001 and the BRAKE
solenoid LOQ2 and hence they are driven by a large
current.
d. When 0534 is OFF, 0533 is ON so the base of 0532
is biased by Q561. As a result, the bias voltage is
reduced to about 12V, causing the voltage at the
emitter of 0432 to be reduced to about 10V and thus
the solenoid is held closed at about 10V during the
PLAY mode.
3.4 Tape end detect circuit
+12v +10V
Fig. 3-3 Tape end detect circuit
Qoo1
Photocoupler
Right reel disk
Light shield drum
Fig. 3-4 Tapedrive detect mechanism
Fig. 3.3 shows the counter pulse generator circuit which
also serves as the tape end detection circuit. Detection
of tape end is accomplished by the mechanism shown in
Fig. 3.4 When the right reel disk is rotating, the light
shield drum attached to the reel disk also rotates.
The light shield drum has two slits; photocoupler Q001
contains a light emission diode and a photo transistor.
The light from the light emission diode arrives at the
photo transistor only when the slits in the light shield
drum pass through the photocoupler, energizing the
photo transistor.
When the light is blocked, the photo transistor is OFF.
In other words, the photo transistor turns on twice
for each rotation of the right reel disk. Since the photo
10
Tape slack
removal signal
transistor’s ON time is not stabilized and since it is de-
energized between ON and OFF according to the posi-
tion of the light shield drum, the waveform of the signal
must be shaped by the Schmitt circuit consisting of
Q545 and O546.
As shown in Fig. 3.5, Q545 turns ON when the voltage
is below 1.3V. Operation of 0546 is the reverse of
Q545.
The shaped output waveform is applied to Pin 6 of
Q701.
When the output pulse from 0546 stops in the PLAY,
FF or REW mode, the microcomputer detects the end of
the tape and the tape stops 1.5-2 seconds later.
Fig. 3-5 Schmitt operation
OFF
Q545
ON
13V 2.0V
Q545 Base Voltage
3.5 Reel motor drive circuit
(1) Reel motor driver
Fig. 3-6 Reel motor driver
REEL MOTOR
MOO2
REEL MOTOR DRIVE
"Servo
, amplifier
15V
QMO8
Eset et ed
p-----|-------
Q701:27 —~ FF
(CUE)
701-28 — . REW
(REVIEW) SR7IOSR7II
R569 0578
Under normal circumstances, QMO9 is OFF and the base
of QM10 is biased via RM12. The voltage at the emitter
of QM10 is about 14V (load). When a high level FF
signal is output from the microcomputer via Q701,
QMO6 turns ON via R570 and RMO9Y. This reduces the
signal level at the collector and thus QMOQ2 turns ON.
As a result, a current flows into the base of QM0O5 which
will turn ON.
In the reel motor M002, a current flows along the route
QMO02 — M002 — OQMO5 — OMO8 so that motor runs in
the counterclockwise direction (as viewed from the
pulley side) to drive the right reel disk.
The transistor OMO8 in the servo amplifier functions
as a variable resistor, controlling the reel motor current
to provide a constant tape speed (refer to Item 3-8
“ery,
In the REW mode, QM07, OMO3 and OM04 turn ON.
In this case, a current flows into M002 along the route
QMO03 — M002 — OM04 — OMO8, so the motor runs in
the reverse direction of this FF mode.