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FILTER BLOCK
Since the sound signal from the CPU is a stepped waveform, the filter block is added to smooth the waveform.
Amp.
IC301
POWER AMPLIFIER (IC301: LA4598)
The power amplifier is a two-channel amplifier with standby switch.
The following table shows the pin function of IC301.
Pin No.
Terminal
1
Power GND
2
Ch1 B.S.
3
Ch1 OUT
4
VCC
5
Ch1 N.F.
6
Ch1 IN
7
D.C.
8
Pre GND
9
Stand by
10
Ch2 IN
11
Ch2 N.F.
12
Ch2 OUT
13
Ch2 B.S.
14
NC
LED DRIVING
7-segment LED
LED
La ~ Lg
Latch
IC3
(Segment)
LED
Latch
IC2
Q2 ~ Q4
(Common)
Filter Block
Q305
In/Out
In
Ground (0V) source
—
Terminal for a bootstrap capacitor
Out
Channel 1 output
In
+9V source
In
Negative feedback input
In
Channel 1 input
—
Terminal for a decoupling capacitor
In
Ground (0V) source
In
Power control signal input. 0 V: Off, +9 V: On
In
Channel 2 input
In
Negative feedback input
Out
Channel 2 output
—
Terminal for a bootstrap capacitor
—
Not used
MD0 ~ MD3
MWEB
MSM6755B-13
MD4 ~ MD7
MA0
— 5 —
Function
Keyboard LEDs
LX0 ~ LX7
CPU
LSI1
LY1 ~ LY7
CPU
LSI1
LVDD
Q5 ~ Q8
Q1 ~ Q4
LG
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