Kenwood KT-7020 Service Manual

KT-7020
CIRCUIT DESCRIPTION
Function of components
Tuner unit (X05-342X-XX)
Components
Use/Function
Operation/Condition/Interchangeability
Q1 FM RF amplifier
Q2 Mixer
a3 FM OSC (TUNED) buffer
Q4,5 | FM OSC
Q6
OSC
buffer
For
PS.
Qs
Regulator
(control)
12V
power
supply
for
FM
circuitry.
ag Regulator (error amplifier)
Q10
7
AM
power
switch
|
Power
switch
for
AM
circuitry.
Q11
FM/AM
power
controi
When
the
base
is
“H"
(set
by
5V
from
the
microprocessor),
Q10
is turned ON setting the AM mode.
Q12~14
PLL loop filter
Q17,18
Q22
Q34
DIS/DIR switching
Goes ON when the input is “H”. Turns Q17 and Q18 ON.
DIS/DIR switching
WIDE/NARROW switching
STOP control
STOP SENS switching
REC CAL control
AM switching
REC CAL switching
Forced Mono control
Auto quieting control
Driver. Q17 is ON for DiS and Q18 is ON for DIR.
When
the
input
to
Q19
is
“H",
Q20
is
turned
ON
(Wide).
When
the
output
from
IC8
(2/2)
is
“L".
Q22
is
turned
ON
and
the
STOP
signal
goes
"L”.
SENS is High when the input is “H”.
REC CAL is set when the input to 024 is “H”.
Switches the AM signal.
Switches REC CAL.
Forced Mono mode is set when the input is “H™.
Automatically
controls
the
SUB
demodulation
level
during
the
small
antenna
input
operation.
Q35
38kHz
sine
wave
generator
amplifier
Using
the
tuning
circuit
(38kHz)
of
LC
as
the
load,
turns
the
rectangular
wave
into
a
sine
wave.
Q36
38kHz
buffer
amplifier
I
Sends
the
38kHz
signal
from
the
tank
circuit
to
the
SUB
demodulator at a low impedance.
Q37
circuit
Current
mirror
constant-current
|
Used
as
the
load
resistance
to
IC
18.
Performs
current
regulating
operation
together
with
Q37.
Used
as
the
load
resistance
to
IC18.
i
Performs
current
regulating
operation
together
with
Q39.
|
Constant-current
load
(GND
side).
Gain switching
|
Goes
ON
in
Narrow
mode
to
control
the
separation
(Narrow).
Q44
_[
sus
signal
demodulation
switching
|
OFF
in
Stereo
mode,
ON
is
Mono
mode.
Q51,52
|
OUTPUT
muting
Used
for
muting
the
output
signal.
053.54
Muting
control
Muting
is
activated
when
the
base
of
Q54
is
“L”.
Qs5
=f
Regulator
[
Main
15¥V
output.
Regulator
—13V output.
Q60
Q56,.57
Q58,59 Regulator
Q61
Regulator For +5V PLL. prescaler IC.
Regulator
PANT
On
For +28V Vt.

Kenwood KT-7020 Specifications

FM Tuner Section

tuning frequency range	87.5 MHz - 108 MHz
usable sensitivity (MONO)	0.95 µV/10.8 dB
total harmonic distortion (MONO)	0.007%
signal to noise ratio (MONO)	92 dB
stereo separation (1 kHz)	65 dB
capture ratio	1.0 dB (WIDE)
alternate channel selectivity (+400 kHz)	60 dB (WIDE)
image rejection ratio (at 98 MHz)	82 dB
IF rejection ratio (at 98 MHz)	110 dB
spurious rejection ratio (at 98 MHz)	105 dB
AM suppression ratio	76 dB
frequency response	20 Hz - 15 kHz, +0.5 dB, -0.5 dB
output level/impedance	0.6 V/3.3 kΩ

AM Tuner Section

tuning frequency range	531 kHz - 1, 602 kHz
usable sensitivity	10 µV (350 µV/m)
signal to noise ratio	55 dB
total harmonic distortion	0.25%
image rejection ratio (Loop)	40 dB
selectivity	30 dB
output level/impedance	0.18 V/3.3 kΩ

General

power consumption	20 W
dimensions (W x H x D)	440 mm x 98 mm x 318 mm
weight	4.3 kg