4
F-20B
CIRCUIT BOARD LAYOUT
MAIN 1/2
MAIN 1/2
MAIN 1/2
MAIN 2/2
MAIN 2/2
AC Cord
Power Transformer
BLOCK DIAGRAM
+B
+12V
-12V
-B
GND
POWER
AMP
IC4
IC1
IC3
1
2
31
1
4
INPUT
FUSE
FZ1
ACTIVE TYPE
TONE CONTROL
POWER SUPPLY CIRCUIT
POWER TRANSFORMER
4Ω Speaker
PHONE
AUX IN
CN2 4P
CN1 2P
CN3 3P
CN4 5P
CN5 5P
POWER SWITCH
SW1
T2
T1
T4
T1
T2
G
U, C, S, BS
MAIN 1/2
MAIN 2/2
T3
GAIN SELECT
ACTIVE CH.
PASSIVE CH.
BASS
VR5
LOW MID
VR4
HIGH MID
VR3
TREBLE
VR2
VR1
IC3
57
VOLUME
JK3
JK2
JK1
SW2
IC1,IC2
OP AMP
OP AMP
8
4
+12V
-12V
-B
+B
5
3
+12V
-12V
8
4
Top View Side View
Front View