Circuit Description - Kenwood KDS-100 Service Manual

KDS-100
1. Power Supply Circuit
The KDS-100 power supply circuit uses a dedicated regu-
lator IC for each circuit application so that the circuits do not
interfere with each other. (Figure 1)
IC36
SB 8V
IC30
IC35
2. LCD Backlight Intensity Adjustment Circuit
The intensity of the backlight of the KDS-100 LCD assem-
bly is adjusted by controlling the Q7 base voltage with the D/
A converter (IC17) and changing the Q8 collector voltage.
(Figure 2)
IC17
D/A converter
R171
ch1 out
2
3. Audio Amplifier Circuit
The KDS-100 audio amplifier (IC34) amplifies the beep
signal generated by the microcomputer to the level for out-
putting to a speaker.
The audio amplifier power supply is turned ON or OFF
according to the timing that sounds a beep with a shift regis-
ter (IC24) controlled by the CPU (IC6). The volume is con-
trolled according to the DC voltage of the D/A converter
(IC17) controlled by the CPU. (Figure 3)
6

CIRCUIT DESCRIPTION

IC32
5V
CPU, DIGITAL
IC33 IC26
5V 1.8V
DSP CORE
IC31 IC27
5V 3.3V DSP I/O
IC28
3.3V
ANALOG
ANALOG
5V
to CN15
5V
to CN16
Fig. 1
8V
R236
Q8
Q7
Fig. 2
Beep
Q10
5V
IC24
Shift register
12
Q6
R193
3
ch2 out
10
ch3 out
R195
IC17
D/A converter
Fig. 3
4. Key Backlight, TX/RX LED Control Circuit
The KDS-100 front operation key backlight and TX/RX sta-
tus indicator LED is turned ON or OFF with the shift register
(IC24) controlled by the CPU (IC6). (Figure 4)
5V
Q6
6
RX Q0
7
TX Q1
11
KEY Q5
8V
IC24
Shift register
Fig. 4
5. Digital Control Circuit
■ Overview
The KDS-100 control circuit consists of a CPU (IC6) and a
DSP (IC23).
The DSP functions as a MSK modem.
Figure 5 is a block diagram of a digital control circuit.
IC6 Address
CPU data bus
Fig. 5
IC34
5
INT. SP
Vp
4
Vin(1)
6
Vin(2)
EXT. SP
2
Vc1
8
Vc2
D27
Q9
IC23
DSP