Casio WK-1800 Service Manual page 22

POWER AMPLIFIER (IC201: LA4663)
The power amplifier is a two-channel amplifier with standby switch.
SIGNAL
MUTE
IN1
PRE
GND
IN2
STAND BY
5
6
CH 1
+
2
–
Ri=
20k Ω
Input amplifier
3
Input amplifier
+
4
–
Ri=
20k Ω
CH 2
1
Ripple Filter/
Starting Time
V CC 1 V CC 2
7 8
Output amplifier
V cc /ground shorting
protection circuit
Load shorting protection circuit
Thermal protection circuit
Protection circuits
Output amplifier
— 21 —
+
3 OUT1
PER
13
GND1
–
12
OUT1
+
OUT2
9
PWR
10
GND2
–
11 OUT2