Kenwood TK-863G Service Manual page 21

APC Circuit
The automatic transmission power control (APC) circuit
detects part of a power module output with a diode (D35,
D36) and applies a voltage to IC15. IC15 compares the APC
control voltage (PC) generated by the D/A converter (IC6)
and DC amplifier (IC7) with the detection output voltage to
control Q31 and Q32, generates DB voltage from B voltage,
and stabilizes transmission output.
The APC circuit is configured to protect over current of
the power module due to fluctuations of the load at the an-
tenna end and to stabilize transmission output at voltage
and temperature variations.
Q22,25 Q27
RF RF POWER
D16
AMP AMP
DB
DRIVER
Q33 Q31
TEMP
PROTECT DRIVER
IC7 IC15
PC
DC
IC6
AMP CONTROL
23pin
Fig. 9 APC circuit
Control Circuit
The CPU carries out the following tasks:
1) Controls the shift register (IC9, IC510) AF MUTE, WIDE/
NARROW, T/R KEY outputs.
2) Adjusts the AF signal level of the audio processor (IC508)
and turns the filter select compounder on or off.
3) Controls the DTMF decoder (IC511).
4) Controls the LCD assembly display data.
5) Controls the PLL (IC3).
6) Controls the D/A converter (IC6) and adjusts the volume,
modulation and transmission power.
LCD ASSY
IC510
Shift
register
IC508
Audio
processor
AFCLR
AFMSKE
AFSTB
DTMDAT
IC511
DTMF
DTMCLK
DECO.
DTMSTD
Fig. 10 Control circuit
CIRCUIT DESCRIPTION
ANT
IC400 D30
ANT
LPF
AMP SW
Q32
D35,36
APC POWER
+B
DET
PRI
APC
TX-RX UNIT (A/2)
IC9
Shift
register
IC6
D/A
DAST
converter
IC502
CPU
PLST
PLDT
IC3
PLL
PLCK
Memory Circuit
The transceiver has a 2M-bit (256k x 8) flash ROM
(IC501) and an 8k-bit EEPROM (IC505). The flash ROM con-
tains firmware programs, data and user data which is pro-
grammed with the FPU. The EEPROM contains adjustment
data. The CPU (IC502) controls the flash ROM through an
external address bus and an external data bus. The CPU
controls the EEPROM through two serial data lines.
ADDRESS BUS
IC501
FLASH
ROM
DATA BUS
Fig. 11 Memory circuit
Display Circuit
The CPU (IC502) controls the shift register (IC510) and
display LEDs. When the LED1 line goes high when the
transceiver is busy, Q508 turns on and the green LED on
D521 lights. In transmit mode, the LED0 line goes high,
Q504 turns on and the red light lights. Backlighting LEDs for
the key operation unit (D509~D514) and LCD are provided.
When the MBL line goes high, Q506 turns on, then Q505
turns on, and the key illumination LED lights. A voltage is
applied to the MBL line to turn on the LCD backlight.
MBL
Q506
SW
IC510
LED1
Q508
Shift
SW
register
LED0
Q504
SW
Fig. 12 Display circuit
Key Matrix Circuit
The TK-8603G front panel has function keys. Each of
them is connected to a cross point of a matrix of the KIN0 to
KOUT2 ports of the microprocessor. The KOUT0 to KOUT2
ports are always high, while the KIN0 to KIN2 ports are al-
ways low.
The microprocessor monitors the status of the KIN0 to
KOUT2 ports. If the state of one of the ports changes, the
microprocessor assumes that the key at the matrix point
corresponding to that port has been pressed.
KIN0
KIN1
KIN2
IC502
KOUT0
CPU
KOUT1
KOUT2
Fig. 13 Key matrix circuit
TK-863G
SCL
IC502
IC505
SDA
CPU
EEPROM
MBL
MBL
Q505
SW
D509~514
D521
GRN
RED
VOL VOL
DN UP
D/A GRP A
DN
SYS SYS GRP
UP
DN UP
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