Power Supply - Kenwood TK-361SA Service Manual

TK-361SA
IC101 (2/2) compares the output voltage of IC101 (1/2)
with the reference voltage from MCU (IC405). The output of
IC101 (2/2) controls the VG of the RF power amplifi er, Drive
amplifi er and Pre-Drive amplifi er to make both voltages the
same.
The change of power high/low is carried out by the
change of the reference voltage.
■ Encode Signaling
• QT/DQT
QT,DQT data of the QTTCXO Line is output from pin 28
of the MCU (IC405). The signal passes through a low-pass
CR fi lter and goes to the TCXO (X1).
The QT,DQT data of the QTVCO Line is output from pin
24 of the MCU. The signal passes through a low pass CR fi l-
ter, mixes with the audio signal, and goes to the VCO modu-
lation input. TX deviation is adjusted by the MCU.

5. Power Supply

There are four 5V power supplies 5M, 5C, 5R, and 5T.
5M for MCU (IC405) is always output while the power is on.
5M is always output, but turns off when the power is
turned off to prevent malfunction of the MCU.
5C is a common 5V and is output when SAVE is not set
to OFF.
5R is 5V for reception and output during reception.
5T is 5V for transmission and output during transmission.
6. Control Circuit
The control circuit consists of a MCU (IC405) and its
peripheral circuits. It controls the TX-RX unit. IC405 mainly
performs the following:
(1) Switching between transmission and reception by the
PTT signal input.
(2) Reading system, group, frequency, and program data
from the memory circuit.
(3) Sending frequency program data to the PLL.
(4) Controlling squelch on/off by the DC voltage from the
squelch circuit.
(5) Controlling the audio mute circuit by the decode data in-
put.
(6) Transmitting tone and encode data.
■ Frequency Shift Circuit
The MCU (IC405) operates at a clock of 7.3728MHz. This
oscillator has a circuit that shifts the frequency by BEAT
SHIFT SW (Q407, Q408).
A beat sound may be able to be evaded from generation
if "Beat Shift" is set to ON when it is generated in the inter-
nal spurious transmission modulated sound of a transceiver.
IC405
XIN
MCU
XOUT
BSHIFT
Fig. 7 Frequency shift circuit
10
CIRCUIT DESCRIPTION
X2
Q408
H: OFF
L: ON
Q407
H: OFF
L: ON
■ Memory Circuit
Memory circuit consists of the MCU (IC405) and an EE-
PROM (IC406). An EEPROM has a capacity of 64k bits that
contains the transceiver control program for the MCU and
data such as transceiver channels and operating features.
IC405
MCU
Fig. 8 Memory circuit
■ Low Battery Warning
The battery voltage is checked by the MCU (IC405).
The transceiver generates a warning tone when it falls
below the warning voltage shown in the table.
(1) The red LED blinks when the battery voltage falls below
the voltage (1) shown in the table during transmission.
Note:
The transceiver checks the battery voltage during recep-
tion even when, in the FPU, the Battery Warning status
function is set to "On TX" (default setting).
However, the LED does not blink during reception. Dur-
ing transmission, the LED blinks to generate the warning
tone of a low battery voltage.
(2) The transceiver immediately stops transmission when
the battery voltage falls below the voltage (2) shown in
the table. A message tone beeps while the PTT switch is
released.
(1)
(2)
R404
88
SB
Fig. 9 Low battery warning
7. Control System
Keys and channel selector circuit.
The signal from keys and channel selector input to MCU
(IC405) directly as shown in fi g. 10.
Channel selector
IC405
MCU
50
EN1
49
EN2
48
EN3
47
EN4
46
EN5
Fig. 10 Control system
IC406
EEPROM
Ni-Cd Battery
6.2V
5.9V
IC405
BATT
MCU
27
PTT
PTT SW
74
PF1
SW1
75
PF2
SW2