Kenwood TM-D700A Service Manual

TM-D700A/E
CIRCUIT DESCRIPTION
4.PLL circuit
4-1.Reference oscillator circuit
The 12.8MHz signal is generated by the crystal oscillator
circuit (IC1 and 1C301) and internally divided to generate 5kHz
or 6.25kHz reference frequency. The 12.8MHz signal on IC1
side is tripled by Q102 to obtain the second local oscillator for
the A band. The reference oscillation circuit is also modulated
to improve the modulation characteristics of the DCS and
9600bps packet signal when it is transmitted.
VHF VCO
CV IC2
KCH38
CHARGE PUMP PLL
Q1 28A1774(S) iC1
Q2 28C4617(R) MB1511PFV-GBND
- i LD
Co] 12.8MHz
Qi102
28C4649] x3
{N,P)
38.4MHz
UHF VCO
CV | icso2 HT
KCH28
CHARGE PUMP PLL
Q304
28C5108
(¥)
Q300 2SA1774(S) 1C304
Q301 2SC4617(R) M8151 1PFV-GBND
L U_________» ip
CJ 12.8MHz
7
Fig.12 PLL curcuit
4-2.Phase comparator
Part of the VHF VCO output is amplified by Q3 and goes to
VHF PLLIC. Also, a part of the UHF VCO output is amplified by
Q302 and goes to the UHF PLL IC. The pulse-swallow type
PLL IC divides the input VCO oscillator frequency using the
data from the CPU (IC604). It compares its phase with that of
the reference frequency to make the PLL synthesizer to
generate the desired step.
4-3.Lock voltage (VCO control voltage)
The phase differencial comparator, output from the PLL IC,
results in a phase difference pulse. This pulse is amplified by a
charge pump (Q1, Q2 or Q300, Q301), the ripples are removed
by a low-pass filter .Then the signal is supplied as the oscillator
frequency control voltage for each VCO.
4-4.Unlock detection circuit
When the PLL is unlocked, a low state voltage is outputed
from pin 8 of the PLL IC.
This signal is monitored by the CPU (IC604) to control
transmission/reception ‘switching timing.
5. Power supply circuit
5-1.Microcomputers and peripheral circuits
Reset and backup circuits
The
CPU
reset
signal
is
generated
by
detecting
a
rising
edge
of
the
M5C
line
voltage
with
the
reset
IC (IC601).
The
TNC
reset
pulse
is
generated
by
Q3
at
a
rising
edge
of
VDD.
When
the
voltage
supplied
to
the
transceiver
decleases
and
the
B
line
voltage
falls
below
the
detection
voltage
of
the
voltage
detection
circuit
(Q604,
D604),
the
CPU
(IC604)
detects
it
through
the
interrupt
pin,
stores
data
in
the
EEPROM
(IC602),
and
shuts
the
power
off.
5-2.Voltage detection processing
The
CPU
(iC604)
monitors
and
process
various
voltage
status
at
iC604
A/D
ports.
The
squelch
voltage
is
input
from
the
IF
IC
and
a
change
in
the
noise
voltage
is
detected
to
control
squelch.
The
S
meter
voltage
is
input
from
the
IF
IC
to
control
the
S
meter
display.
The
thermistor
voltage
(temperature)
and
the
remote
control
microphone
key
operation
are
also
detected
throuyh
the
A/D
port.
11

Kenwood TM-D700A Specifications

General

Brand	Kenwood
Model	TM-D700A
Category	Transceiver
Language	English