RTS DV 2400 Series, Service Manual

Page: 6 / 40

DV-2400
5
CIRCUIT DESCRIPTION
RF AM P
Q208 and Q219
DRIVE STAGE
Q212
DRIVE AMP
Q2 14
FINAL AM P
Q215
ANT
ANT SW LPF
POWER
DET
D2 28 ,D229
APC
CONTROL
VR2 00
U2 02
14pin
U5 05
PC
D214 ,D21 5
D202
at the antenna end and to stabilize transmission output at voltage and temperature variations. (See Fig.
9.)
Fig. 9 APC Circuit
Control Circuit
The CPU carries out the following tasks (See Fig. 10.):
1) Controls the WIDE, NARROW, TX/RX outputs.
2) Controls the display unit.
3) Controls the PLL (U205).
4) Controls the D/A converter (U505) and adjusts the volume, modulation and transmission power.
CK
D/A
DT
LD
LE
U505
converter
U205
PLL
U2
CPU
Fig. 10 Control circuit
„
Memory Circuit
The transceiver has an 128k-bit EEPROM (U6). The EEPROM contains adjustment data. The CPU (U2)
controls the EEPROM through two serial data lines. (See Fig. 11.)
U6
EEPROM
U2
CPU
Fig. 11 APC Circuit
„
Display Circuit
The CPU (U2) controls the display LCD and LEDs. When power is on, the CPU will use the P07 line to
control the LCD illumination and key backlight LEDs.
The brightness function is controlled by the switch Q6 and Q7.
The LCD driver (DS1) and CPU (U2) communicate through the P14, P15, P16, P17, P85, P86 lines.
(See Fig. 12.)