Yamaha GX-900 Service Manual page 76

A B C
GX-900
SCHEMATIC DIAGRAM (INPUT)
1
INPUT SELECTOR
0
0
0
0
0
2
0
0 -9.1
0 0
0
0
0
0
0
0
3
0
0
0
4
SAME
MOTOR
PAGE
D-8
DRIVE
12.5
5
SAME
PAGE
0
M-8
HEAD EQ AMP
DOLBY B-TYPE
PROCESSOR
CASS IN CASS
SAME
PAGE
M-9
6 ~
~
0
TAPE SPEED ADJ.
0
11.7
0.7
0 0
12.4
0
12.4
0
MECHANISM
7
CONTROL
BIAS ADJ.
SAME
PAGE
N-8
BIAS ADJ.
(Lch)
REC/PB
8
SW
P90
I-5
TUNER
MD
CD
P86
L-2
9
SAME
P85 P85
IC1 : LB1641
H-5 PAGE
B-1
Motor Driver K-6
3 2 8 10 9 7
µ
IC2 : PC1330HA
2 ch Head Selector Switch
10 4 VZ
INVERTER
COMPARATOR
1 2 3 4 5 6 7 8 9
INPUT LOGIC
IN 1 5 6 IN 2
GND 1
87
D E F
The voltages are measured by Type II/High tape at PLAY mode (no-signal condition)
Only the voitages ( ) are at REC (CD) mode.
DOLBY NR OFF
8.9
8.9
0 0
8.9
0
0
8.9
0 0
4.7
0
0
0
-9.1
0
0
0
-9.1
8.9
7
8.9 -9.1
14
0 0
0
-9.1 0 0
0 8.9
0 0
0
4.7
8.9
0 0
0
0
0
4.7 8.9
8.9
0
8.9 8.9
0 0
8.9 8.9
0 0
4.7
4.7
0 0
TAPE
PB
(4.7) (0) 0
PB LEVEL ADJ.
(Lch)
0
(0) REC LEVEL ADJ.(Lch)
0
0
(0)
(0) 0 (0)
(4.3)
4.3
(2.6) 2.6
(2.6)
2.6 (4.2) 4.0
(1.3) (1.6) 0
1.3
(1.2) 1.2 (0)
0 (0)
(0) 0
0
(1.3) (4.2) 4.2
1.3
(4.3) 4.2
(0) 0
(2.4)
(2.6)
(7.4) 7.4 2.4 (2.4)
2.6 2.4
0
(0)
4.2
(4.2)
4.3
(8.5)
(4.3)
8.5
REC LEVEL ADJ.
(Rch)
2.5 (2.5)
PB LEVEL ADJ.
0 (0)
(Rch) 0 (0)
0
(0)
0
(0) 0 (0)
0 0 (0)
(0)
0
(0)
BIAS OSC
(Lch)
CASS
23.1
(3.5) 0 (20.7)
3.4
(15.8)
0
(0)
(15.7) (0) 0
0
(16.4)
(5.5)
0 0 (16.4)
0
(0) (0) 0
0 0
4.7 (0)
(0.2)
4.9
(4.9)
0 0
(0) (0)
SAME PAGE A-5 P85 B-8 P86 L-3
3.6
0
0
0 0
0 2.4
0 3.9
0 0
4.7
0
0 4.7
0
3.1
INPUT (2)
IC3, 4 : TC4052BF µ
IC5 : PD4066BG
Dual 4 Channel Analog Multiplexers/Demultiplexers
Quad Analog Switch/Multiplexer
INHIBIT VDD
6 16
IN/OUT 1 14 V DD
A LEVEL BINARY TO 1-OF-4
10 SW
B 9 CONVERTER DECODER WITH INHIBIT SIG/A 13 CONT A
A
VSS 8
OUT/IN
VEE 7 2
X0 12 SW SW
OUT/IN 3 12 CONT D
D
X1 14 SW SIG/B
X
13 IN/OUT 4 11 IN/OUT
X2 15 SW
SIG/D
SW
X3 11 SW CONT B 5 10 OUT/IN
B
INHIBIT B A
Y0 1 SW
0 0 0 0x, 0y 9 OUT/IN
Y1 5 SW
0 0 1 1x, 1y
3 Y SW
CONT C 6 SIG/C
Y2 2 SW 0 1 0 2x, 2y C
0 1 1 3x, 3y
Y3
4 SW V SS 7 8 IN/OUT
1 X X NONE
G H
P88
F-1
ELECTRONIC
VOLUME
CONTROL
4.4 4.4
4.4
8.9 4.4
4.4
4.4
0
0
2.3
4.7
0
0
4.4 4.4
4.4 4.2
4.4
4.3
4.4
4.4
12.3
0
0
0
TONE
AMP
0
0
0
-12.0
(0)
(4.5) (4.5)
0
0 0
0 (0)
~ (~)
(4.9)
4.9
4.6 (4.6)
(4.9)
4.9
0 (0)
4.9 (4.9)
r 0 (0)
4.8 (4.9)
~
0 (0)
~
0 (0)
1.7
4.8 (4.9)
1.7
4.8 (4.9)
e
4.7 (4.7) 0
4.1 (4.1) 2.3 (2.3)
1.9 (1.9)
0 (0)
(2.3)
2.3
0 (0) MAIN CPU
2.2 (2.1)
4.1 (4.1)
4.6 (4.6)
~ (~)
(4.6)
4.6
(0) 0 (4.9)
RESET 4.9
(0) 0
4.8 5.2
(4.9) (5.2)
4.8
(4.8)
4.6
(4.6) 0
(0)
(0)
5.5 0 0
(5.5)
2.1
(2.1)
0
(0)
t
5.5
P88 P88
E-6 H-5
IC401 : TC74VHC153F
Dual 4 to 1 Data Selectors
Point e (Pin37 of IC8)
H : 20 µsec/div
STROBE A DATA INPUTS OUTPUT V : 2V/div
VCC 2G SELECT 2Y
DC range 1 : 1 probe
16 15 14 13 12 11 10 9
2C3 2C2 2C1 2C0 2Y
2G
B B A A
INPUTS OUTPUT
0V
SELECT STROBE
Y
B A G
B B A A
X X H L
1G
1C3 1C2 1C1 1C0 1Y L L L C0
L H
L C1
H L L C2
1 2 3 4 5 6 7 8
H H L C3
STROBE B OUTPUT GND
DATA INPUTS
1G SELECT 1Y
I J K
BUFFER
MUTING
12.3
0
0
0 0
5.5
-12.0
0 -11.9
4.7
-11.9
0
0
0
8.9 12.4
9.6
9.6
0
REGULATOR
3.7 3.7
12.4
4.9
5.5
5.5
4.7
1.9
-6.0
5.6 0
0
MUTING
12.3
0
0
0
0 -6.0
PRE
0
AMP
0
-6.0
0
0
0 0
-12.0
9.0 12.4
9.7
9.7
0
P89
A-3
REGULATOR
REGULATOR
5.5
SAME
9.6
PAGE
6.2
B-9
6.2
0
SPECTRUM
ANALYZER
1.0
µ
IC9, 11, 21 : PC4570G2
0.4 0.9
Dual OP-Amp
OUT 1 1 8 +V CC
–IN 1 2 7 OUT 2
+ – + –
+IN 3 6 –IN
1 2
–V 4
CC 5 +IN 2
INPUT (1)
Point t
CH1 : Collector of Q19 V : 2V/div (CH1)
CH2 : Anode of D11 V : 2V/div (CH2)
H : 0.5 sec/div DC range
(This waveform is not available by pushing the power switch ON and OFF.)
Point r (Pin39 of IC8) CH 1
V : 2V/div H : 50 nsec/div
DC range 1 : 1 probe
CH 2
0V
With the POWER ON,
disconnect the A/C power
cord. Reconnect the A/C
power cord and the above
waveforms will start.
L M N
IC6 : CXA1897Q
Dolby B-Type Noise Reduction System with Recording/Playback
Equalizer
48 47 46 45 44 43 42 41 40 39 38 37
VCC 1
36 GND
GND
RFC 2 IREF
35
AMS OUT 3 34 VG
IREF
VCC
AMS GAIN 4 33 AGC TC
10K 10K
AGC IN1 5 32 AGC IN2
AGC
AGC OUT1 6 31 AGC OUT2
D REC IN1 7 30 D REC IN2
D IREF 8 IREF MUTE 29 REC MUTE
D PB IN1 9 28 D PBIN2
REC REC
EQ EQ
NRSW 10 27 MODE
D L OUT2 11 26 D L OUT2
REC EQ REC EQ
CTL CTL
D TC1 12 D TC2
25
13 14 15 16 17 18 19 20 21 22 23 24
IC7 : LC75393E
Electronic Volume Control
RSBC2 33 16 LSBC2
RHP1 34 15 LHP1
RHP2 35 14 LHP2
RRECOUT10 36 13 LRECOUT10
RRECIN10 37 12 LRECIN10
RRECOUT1 38 11 LRECOUT1
RCOM1 39 10 LCOM1
RH 40 9 LH
RF2C1 41 8 LF2C1
P89
A-4
RF2C2
42 7 LF2C2
RF2C3
43 6 LF2C3
RF1C1 44 5 LF1C1
RF1C2 45 4 LF1C2
RF1C3 46 3 LF1C3
RTIN 47 2 LTIN
P89
RSVROUT 48 1 LSVROUT
H-7
IC26 : BA3835S
5-Band BPF and Peak Hold for Spectrum Analyzer
BIASC 1 BIAS 18 GND
VREFC 2 VREF 17 A OUT
REFFERENCE
BREF 3 16 TEST
CURRENT
105Hz PEAK
N. C. 4 15 N. C.
BPF HOLD
RES
N. C. 340Hz PEAK N. C.
5 14
BPF HOLD
RES
A – C 1kHz PEAK
DIF OUT 6 MPX 13 SEL
BPF HOLD
RES
C 3.4kHz PEAK
C IN 7 DIF 12 C
BPF HOLD
RES
A 10.5kHz PEAK
A IN 8 HOLD 11 B
BPF
RES
VCC A
9 10
DEC
+
1. Lch +
L
2. Lch — SAME
R / P HD —
3. Rch —
PAGE
R
4. Rch +
+
— A-7
5. E —
E HD
6. E +
+
PH CONNECTOR
IC10 : BA15218N
LOADING PCB
Dual OP-Amp
1. LOAD OUT (+) 1
MTR
SAME
2. LOAD IN (+) 2
PAGE 3. LOAD OUT 3
+ +
A-5
4. COM 4
– –
5. LOAD IN 5
PH TYPE (JST)
1 2 3 4 5 6 7 8
MAIN PCB
1. R ¥ REC 1
2. METAL 2
3. F ¥ REC 3 SOL
4. CASS IN 4
5. C O 5
SAME r 2
6. +SOL 6
PAGE
7. SENSOR OUT 7
A-6
8. +5V SENSOR 8
1 : 1 probe 9. PLAY SW 9
10. +MTR 10
11. —COM 11 —
+ MABUCHI
B MTR
12. MTR SPEED B 12 A
13. MTR SPEED A 13
PH TYPE (JST) MECHA CHASSIS
* All voltage are measured with a 10MΩ/V DC electric volt meter.
Disconnect the * Components having special characteristics are marked Z and
power cord from
must be replaced with parts having specifications equal to those
the AC outlet.
originally installed.
* Schematic diagram is subject to change without notice.
O