Kenwood TK-7180 Service Manual page 22

TK-7180/7189
6. Power Supply Circuit
The block diagram of the power supply
circuit is shown in Figure 6.
Power is always supplied from +B to
the circuit (5M, +B) that is always started
and the circuits (SB, 8C, 5E, 8T, 8R, 5C, 5R)
controlled by the CPU (IC404). When +B is
supplied to the transceiver, Q801, D805
and IC805, regulate the voltage (5M) which
is supplied to the circuit around the CPU.
The CPU starts.
When the CPU detects that the +B volt-
age is higher than the voltage prescribed
by IC802, the transceiver power (SB) is
turned ON by controlling the SBC signal
(Low: transceiver power OFF, High: trans-
ceiver power ON).
The CPU controls the TXC signal (Low:
Transmission system power OFF, High:
Transmission system power ON) during
transmission to supply power (8T) to the
transmission circuit. The CPU controls the
RXC signal (Low: Reception system power
OFF, High: Reception system power ON)
during reception to supply power (8R, 5R)
to the reception circuit.
When the CPU detects the PSW (Power
Switch) signal, IGN (Ignition Sense) signal
or INT signal, it controls the SBC signal and
turns the transceiver power (SB) OFF.
If +B is not provided to the transceiver,
power is supplied to only the RTC IC
(IC402) through the secondary battery con-
nected with CN401 to back up the clock.
7. Display Circuit
The display unit consists of the Panel CPU (IC902), the
LCD driver (IC903), the TX/BUSY LED, the KEY detection, the
Backlight and the Microphone jack circuits.
The Panel CPU is a 16-bit microcomputer that contains a
64k-byte Mask ROM and a 2k-byte RAM.
The Panel CPU performs serial communication with the
Main CPU (IC404) on the TX-RX unit (B/3) and the Panel CPU
detects keys and sends data communication contents
through the MIC Jack to the Main CPU. The Panel CPU re-
ceives commands from the Main CPU and controls the dis-
play system.
The LCD operates with 1/9 duty under the LCD driver
(IC903) control. The LCD and KEY Backlights are controlled
by Q909. The display brightness of the LCD Backlight can be
changed.
22
CIRCUIT DESCRIPTION
Power supply : 10.8~15.6V
F801
5A
D804 Q802
DET SW
Q811
SW
Q801,D805 IC805
REG AVR
IC801
DET
IC802
DET
PSENS
Q810
SW
IC803
AVR
Q807
IC807
SW
AVR
SBC
Q803
SW
Q806
SW
CPU
5M
Flash memory
Q804
EEPROM
SW
Ext-I/O
CPU #17
Q808
: RST1
SW
RTC IC
IC804
AVR
CN401
Q805
SW
CPU #24 Q809
: INT SW
Fig. 6 Power supply circuit
Q910
IC901
8C
AVR
Mask
ROM
PSW
POWER
SW
IC902
RED
CPU
TX/Busy
LED
GRN
SB
RST2
SHIFT
RXD, TXD
MIC, ME
SPO
GND
Fig. 7 Display circuit
+B
Final amp.
SB
Audio amp, PA connector
Panel block, D-sub block
8C
Internal option
Panel block
5E
Internal option
TX-drive
8T
APC block
ANT SW
TXC
8R
IF block
RXC
VCXO, VCO, PLL IC
IF detection IC
5C
DC/DC converter
D/A converter
MIC amp, AQUA
AF block
5R
IF block
RXC
IC903
LCD LCD
driver
Q909
BLCI
LCD KEY
back back
DIMM
light light
Function
FKEY [1~10]
KEY
12 KEY
12KEY [1~12] (TK-7189
model only)
SB
MIC
HK, PTT, DM, BLC2
jack
SP
TK-7180
model only