17
TK-785
■
APC Circuit
The automatic transmission power control (APC) circuit
detects part of a power module output with a diode (D27,
D30) and applies a voltage to Q21. Q21 compares the APC
control voltage (PC) generated by the D/A converter (IC5)
and DC amplifier (IC6) with the detection output voltage to
control Q19 and Q20, generates DB voltage from B voltage,
and stabilizes transmission output.
Q17 turns the PC signal on or off using 8T so that the
circuit works only during transmission. With stability at low
power in mind, Q29 turns off to optimize the detection volt-
age.
The APC circuit is configured to protect overcurrent 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.
Control Circuit
The CPU carries out the following tasks:
1) Controls the shift register (IC7, IC8, IC508) AF MUTE, T/R
KEY outputs.
2) Adjusts the AF signal level of the audio processor (IC504)
and turns the filter select compounder on or off.
3) Controls the DTMF decoder (IC507).
4) Controls the LCD assembly display data.
5) Controls the PLL (IC300).
6) Controls the D/A converter (IC5) and adjusts the volume,
modulation and transmission power.
CIRCUIT DESCRIPTION
IC5
D/A
converter
IC300
PLL
IC7
Shift
register
IC8
Shift
register
IC508
Shift
register
DT
RFCLK
ES2
EN
OE
CS
CK
DT
ACK
SD
CP
EP
AFCLR
AFMSKE
AFDAT
AFRDT
AFTRD
AFRTM
AFSTB
IC504
Audio
processor
IC507
DTMF
DECO.
IC511
CPU
TX-RX UNIT
LCD ASSY
Fig. 8
Control circuit
RF
AMP
Q203
RF
AMP
Q204
POWER
AMP
IC400
APC
DRIVER
Q19
DB
+B
VR1
Q20
PRI
DRIVER
DC
AMP
IC6
PC
SW
Q17
ANT
SW
D211
LPF
ANT
Q29
POWER
DET
D27,30
Q21
APC
CONTROL
H/L
SW
H/L
IC7 5pin
15W : E (High power)
10W : K (High power)
: "H"
8T
(TX : 8V)
TX :
PC SW ON
D15
PC
IC5
23pin
Fig. 7
APC circuit (K,E type)
RF
AMP
Q202,204
RF
AMP
Q205
POWER
AMP
IC400
APC
DRIVER
Q19
DB
+B
VR1
Q20
PRI
DRIVER
DC
AMP
IC6
PC
SW
Q17
ANT
SW
D209
LPF
ANT
Q29
POWER
DET
D27,30
Q21
APC
CONTROL
H/L
SW
H/L
IC7 5pin
25W (High power)
: "H"
8T
(TX : 8V)
TX :
PC SW ON
D15
PC
IC5
23pin
Fig. 7
APC circuit (M type)
■
Memory Circuit
Memory circuit consists of the CPU (IC511) and a flash
memory (IC510). A flash memory has a capacity of 2M bits
(256k x 8) and contains the transceiver control program for
the CPU and the data for operating features.
This program can be easily downloaded from an external
device. The CPU (IC511) controls the flash memory through
an external address bus and an external data bus. The CPU
controls the EEPROM (IC512) through two serial data lines.
• Flash Memory
Note: The flash memory stores the data containing the
FPU (KPG-62D) program, Security Number (MPT Serial
Number), and firmware program (User mode, Test mode,
Tuning mode, etc.).
This data must be reinstalled when replacing the flash
memory.
• EEPROM
Note: The EEPROM stores tuning data (Deviation,
Squelch, etc.).
Realign the transceiver after replacing the EEPROM.
SCL
SDA
IC511
CPU
ADDRESS BUS
DATA BUS
IC510
FLASH
MEMORY
IC512
EEPROM
Fig. 9
Memory circuit
Содержание TK-785
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