Yamaha GX-900, Service Manual

Page: 74 / 103

A B C D E F G H
1
2
3
4
5
6
I J K L
7
8
GX-900
■
SCHEMATIC DIAGRAM (MD)
* All voltage are measured with a 10M
Ω
/V DC electric volt meter.
* Components having special characteristics are marked Z and
must be replaced with parts having specifications equal to those
originally installed.
* Schematic diagram is subject to change without notice.
85
IC4 : TC74HCT04AF-T1
Hex Inverters IC3, 5 :
µ
PC4570G2
Dual OP-Amp
– +
OUT
1
–IN 1
–V CC
+V
CC
OUT 2
1
2
3
4 5
+IN 1 –IN 2
+IN 2
– +
6
7
8
1A
1Y
2Y
V
DD
6A
1
2
3
4 11
2A 6Y
5A
12
13
14
3A
3Y
5Y
4A
5
6
7 V SS 4Y 8
9
10
Point i (Pin13 of IC2)
V : 2V/div H : 50 nsec/div
DC range 1 : 1 probe
0V
LPF
MUTING
MD CPU
REGULATOR
BACKUP
BUFFER
0
0
4.8
-9.8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0
0
0
0
4.6
0 0 0
4.6
0
0
0
0
4.2
0.1 4.6 4.5
0
2.2
0
0
0
4.7
0
0
0
0
0
0
0
0
0
0
0
0
4.7
4.7
2.3
0
2.1
4.7
4.7
4.7
5.1
5.1
5.5
5.5 4.7
10.9
10.3
0
0
0
1.2
1.2
5.0
10.1
0
0
0
-9.8
0
0
0
-9.8
-9.8
0
0 0 5.0
5.5 5.0
3.1
3.4
5.5
3.8
3.8
0
5.0
0
2.0
0
0
0
0
-9.8
0
0
12.4 6.0
6.6
6.6
0
10.1
0
~ ~
~ ~
~
~
~
i
5
6
8
7
2
3 4
4
1
2
3
1
5
6
8
7
P84
K-7
P87
C-9
P87
E-8
P89
A-3
P87
B-9