Power Supply Circuit; Display Circuit - Kenwood TK-7180 Service Manual

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 voltage 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: transceiver power ON).
The CPU controls the TXC signal (Low: Transmission sys-
tem power OFF, High: Transmission system power ON) dur-
ing transmission to supply power (8T) to the transmission cir-
cuit. The CPU controls the RXC signal (Low: Reception sys-
tem 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.
Power supply : 10.8~15.7V
CIRCUIT DESCRIPTION
F801
Q810
SW
5A
Q807
SW
D804 Q802
SBC
DET SW
Q811
SW
CPU
5M
Q801,D805 IC805
Flash memory
REG AVR
EEPROM
Ext-I/O
IC801 CPU #17
DET : RST1
RTC IC
IC802
DET
CN401
CPU #24
: INT
Fig. 6 Power supply circuit
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.
Q910
IC901
8C
AVR
PSW
POWER
SW
TX/Busy
LED
SB
RST2
SHIFT
PSENS
RXD, TXD
SPO
GND
Fig. 7 Display circuit
+B
Final amp.
SB
Audio amp, PA connector
Panel block, D-sub block
8C
IC803
Internal option
AVR
Panel block
5E
IC807
Internal option
AVR
TX-drive
8T
Q803
APC block
SW
ANT SW
Q806
TXC
SW
8R
Q804
IF block
SW
Q808
RXC
SW
VCXO, VCO, PLL IC
IF detection IC
5C
IC804
DC/DC converter
AVR
D/A converter
MIC amp, AQUA
AF block
5R
Q805
IF block
SW
Q809
RXC
SW
TK-7180
IC903
LCD
driver
Mask Q909
ROM
BLCI
LCD
back
RED DIMM
light
IC902
GRN
CPU
FKEY [1~10]
SB
HK, PTT, DM, BLC2
MIC, ME
LCD
KEY
back
light
Function
KEY
MIC
jack
SP
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