Sony DTC-A8 / PCM-2600 / PCM-2800 Service Manual ▷ View online
— 70 —
Table 6-2. Pin Functions on Sensor Amplifier (CX20115A)
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Pin Name
DRUM COM
DRUM FG IN
DRUM FG OUT
DRUM PG IN
NC
PEAK HOLD
DRUM PG OUT
GND
CAP FG OUT2
CAP FG OUT1
CAP LIM IN
CAP AMP OUT
Vcc
CAP FG IN1
NC
CAP FG IN2
Function
Reference voltage
Drum FG input
Drum FG output
Drum PG input
Drum PG capacitor terminal
Drum PG output
GND terminal
Capstan FG 2multiplicative output
Capstan FG standard output
Capstan limiter input
Capstan preamplifier output
Power supply terminal
Capstan FG inverted input
Capstan FG non-inverted input
I/O
I
O
I
–
O
O
O
I
O
I
–
I
— 71 —
6-3. Drum Servo Circuit
Fig. 6-4. Drum Servo Block Diagram
Fig. 6-5. Drum Servo Waveform Timing Diagram
13
14
1/2
1/2 DIVIDER
SN74HC74
IC519
11
9
DAT DSP
CXD2605Q
IC503
IC1,51 CXA1364R SWP IN
IC803 CXD2605Q SWP
IC803 CXD2605Q SWP
47
39
MECHA MICON
(SERVO PROCESS)
IC502
39
21
SWP
DREF
79
72
9.4MHz
MST-CLK
77
SPEED
PHASE
PHASE
ERROR
DET
PWM
CREATION
71
70
83
DPG
DFG
5
3
DPWM (36.7kHz)
LPF
IC522
1
DEER
PWM
BUFFER
DRON (H:DRUM ON)
DRUM MOTOR
DRIVE
IC1, Q1, 2
M
M904
DRUM MOTOR
19
20
5
6
XROM
CK
XROM
DT
EEP ROM
IC517
(128x8bit)
3
7
SENSOR AMP
IC3 CX20115A
IC3 CX20115A
2
4
FG
PG
PG/FG
VS
XT1I
XT1O
X502
18.8MHz
3
4
1
2
SWP
CREATION
5
6
— 72 —
Circuit Operations
The PG signal and FG signal (24 waves) from the drum motor are first waveform-shaped (IC3) by the sensor amplifier,
after which PG is input to Pin &¡ (DPG) while FG is input to Pin &º (DFG) of the mechanism microprocessor (servo
process, IC502). Inside the mechanism microprocessor (servo process), the SWP (switching pulse) is generated from
these two signals.
DREF (Drum Reference), the reference signal for the drum servo generated inside DAT DSP CXD2605Q (IC503) is
input to Pin &™ (DREF).
Inside the mechanism microprocessor, the speed error is detected from the FG cycle while the phase error is detected by
comparing PG and DREF. After this, they are converted to a basic 36.7 kHz PWM wave in the PWM generator in the
next stage, and output from Pin *£ (DPWM).
These signals are next converted to analog signals in the LPF (IC522), passed through the motor drive (IC1, Q1, Q2) in
the next stage, and used to rotate the drum motor (M904).
after which PG is input to Pin &¡ (DPG) while FG is input to Pin &º (DFG) of the mechanism microprocessor (servo
process, IC502). Inside the mechanism microprocessor (servo process), the SWP (switching pulse) is generated from
these two signals.
DREF (Drum Reference), the reference signal for the drum servo generated inside DAT DSP CXD2605Q (IC503) is
input to Pin &™ (DREF).
Inside the mechanism microprocessor, the speed error is detected from the FG cycle while the phase error is detected by
comparing PG and DREF. After this, they are converted to a basic 36.7 kHz PWM wave in the PWM generator in the
next stage, and output from Pin *£ (DPWM).
These signals are next converted to analog signals in the LPF (IC522), passed through the motor drive (IC1, Q1, Q2) in
the next stage, and used to rotate the drum motor (M904).
Fig. 6-5
shows the drum servo waveform timing. In the drum
servo lock state, the SWP and DREF signals have the same phase-relation as shown in the above mentioned figure. The
drum motor sets into the rotation mode when Pin 5 (DRON) is set to “H” by the ON/OFF control output of the drum
motor. The EEPROM (IC517) connected to the mechanism microprocessor memorizes the data of the DPG adjustment
(adjustment of writing position of recorded data), and each time the power is turned ON, the data is taken into the
microprocessor, added to the above error signals to correct the errors. (Details of the DPG adjustment are provided in
the Electrical Adjustments section of the Service Manual.)
drum motor sets into the rotation mode when Pin 5 (DRON) is set to “H” by the ON/OFF control output of the drum
motor. The EEPROM (IC517) connected to the mechanism microprocessor memorizes the data of the DPG adjustment
(adjustment of writing position of recorded data), and each time the power is turned ON, the data is taken into the
microprocessor, added to the above error signals to correct the errors. (Details of the DPG adjustment are provided in
the Electrical Adjustments section of the Service Manual.)
Table 6-3. Main Frequencies of Drum Servo (Servo Lock)
Recording
Playback
Recording
Playback
SP
LP
MODE
DREF (Hz)
100/3
100/3
50/3
50/3
SWP (Hz)
100/3
100/3
50/3
100/3
DFG (Hz)
800
800
400
800
SP :
Standard Play Mode
LP :
Long Play Mode
DREF : Drum servo reference signal
SWP : Switching Pulse
DFG : Drum Frequency Generator
SWP : Switching Pulse
DFG : Drum Frequency Generator
Table 6-3
shows the main frequencies in the drum servo lock state.
As shown in
Table 6-1
, the drum rotation is 2000 rpm during both recording and playback in the SP mode. During
recording in the LP mode, it is 1000 rpm and during playback, it is 2000 rpm.
Table 6-3
shows the frequencies of
DREF, SWP, and DFG in each mode. At the signal timings in the SP mode shown in
Fig. 6-6
, DREF and SWP have the
same phase during recording and playback. The recording data (REDT) during recording and RF signal during playback
are each output at the timings synchronized with SWP and DREF as shown in the figure.
As for the signal timings in the LP mode, as shown in
are each output at the timings synchronized with SWP and DREF as shown in the figure.
As for the signal timings in the LP mode, as shown in
Fig. 6-7
, as the drum rotation during recording is 1/2 that in the
SP mode, the period of the signals is twice that in the SP mode.
During playback, as the drum rotation is set to the same rotation as the SP mode, which is 2000 rpm, the period of the
SWP and RF waveform is the same as the SP mode. The envelope of the RF signals is not the same, because the trace
angle differs according to the difference in the drum rotation between recording and playback. Consequently, A and A’
and B and B’ mean the RF waveform of the same track.
During playback, as the drum rotation is set to the same rotation as the SP mode, which is 2000 rpm, the period of the
SWP and RF waveform is the same as the SP mode. The envelope of the RF signals is not the same, because the trace
angle differs according to the difference in the drum rotation between recording and playback. Consequently, A and A’
and B and B’ mean the RF waveform of the same track.
— 73 —
Fig. 6-7. Signal Timing (LP Mode)
Fig. 6-6. Signal Timing (SP Mode)
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