Marantz SD9000 - Page 12

(2) Servo circuit
QMio
Refer
to
Fig.
3.7
6
R570
FF (CUE) ANY —
R569 Q578
REW(REVIEW) ——-W-
ea
36
RM37 ome
RM2 vain
CMI3
RMOI
{| MOTOR
ttcmoe | DRIVER
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ds I
RM4I
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|
Moo2
8\, | REEL MOTOR
se !
RMI5
=
RMI3
M21
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=
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RM39
CF
nae
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omos
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ape
le
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OMI
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RMO2
(See
Fig.
3-6)
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ICM22
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2006 =
PHOTO COUPLER Qml2
coe.
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2m
Sec
=
a. Photocoupler Q001 is located on the right reel disk
and Q006 on the left reel disk.
b. In the FF mode, a high level signal from the micro-
computer passes through R507, RM26 and RM21 to
turn QM11 on.
The signal from Q001 is not applied to other circuits
as long as the tape is in the FF mode.
In the REW mode, QM12 is ON and the signa! to
QO006 stops. (The FF mode operation is explained in
the following.)
c. In the STOP mode, CM14 and CM19 are uncharged,
so the base of QM19 is at the GND level. QM19 is
OFF and the collector voltage of QM19 is about
8.2V. When the FF signal of H level is output from
the microcomputer, CM19 is charged through RM26,
QM15 and CM14. The FF signal also biases QM19 for
about 150 msec via RM38. Therefore, QM19 is turn-
ed ON and CM15 is quickly discharged through
RM37 and QM18.
When the voltage (QM20 gate voitage) charged in
CM15 drops, the resistance across the drain and
source of OM20 is increased. With this resistance in-
creased, the DC output voltage from Pin 6 of QMO1
drops and the QMO8 collector current (reel motor
current) is decreased. Therefore, the reel motor starts
running at a slower speed just after entering the FF
mode. When CM14 is charged with the FAST signal,
QM19’s base voitage drops and the collector voltage
is increased. CM15 is charged through RM36 and
RM39 with a long time constant so CM20’s gate volt-
age is increased slowly. As the gate voltage is in-
creased, the drain-source resistance is decreased grad-
ally, while QMO1’s output voltage is slowly increased.
Thus, QMO8’s collector current is increased, thereby
QM23
11
RM46
CMI7 QMO2
rye QMO2 RMa7
Fig. 3-7 Servo circuit
increasing the speed of the reel motor gradually.
Since the reel motor starts running at a slow speed,
the tape will not become slack.
d. In the FF (REW) mode, the tape drive detecting
signal is fed from QM14 (QM13) to Pin 4 of QM21.
QM21 (uPD4528C) is a unistable multivibrator which
outputs low level pulses with a width of about 2
msec, from Pin 7 at the rise of the trigger pulses given
to Pin 4. The pulse-width is determined by the power
voltage, CM16 and RM44. Refer to Fig. 3.8 for the
connection of uPD4528C and its block diagram.
Fig. 3-8-1 Reel motor rising characteristic
H
FF signal
L
H
cCM14©
L
QmM19 H
Collector
bk
H
QM20 Gate
L
H
QM01-6
L
HIGH es
Reel motor
speed
MOo02 STOP