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Harman Kardon HK690 - Page 6

Harman Kardon HK690
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.—lcUra
GENERAL
UNIT
EXPLODED
VIEW
™
Fs
A
B
DISASSEMBLY
PROCEDURES
(REFER
TO
PAGES
5
AND
18)
1|CABINET
TOP
REMOVAL
Remove
6
screws
@
and
then
remove
the
cabinet
top.
FRONT
PANEL
ASSEMBLY
REMOVAL
.
Remove
the
cabinet
top.
(Refer
to
step
[1]
.)
.
Pull
off
Volume,
Bass,
Treble
and
Balance
knobs
(105
and
146).
Remove
6
screws
®
and
then
remove
the
front
panel
assembly.
wo
No
[3]
TUNER
P.C.
BOARD
(PCB-2)
REMOVAL
1.
Remove
the
cabinet
top.
(Refer
to
step
[1]
.)
2.
Disconnect
J302,
J303
and
J351
from
P302,
P303
and
P351
on
the
tuner
P.C.
board
(PCB-2).
3.
Open
the
lid
of
connectors
(P301,
P352
and
P353)
on
the
tuner
P.C.
board
(PCB-2)
and
then
disconnect
the
lead
wires.
4.
Remove
6
screws
@
and
then
remove
the
tuner
P.C.
board
(PCB-2)
with back
plate
(136),
shield
plate
(172)
and
brackets
(181
and
252).
[4]
PHONO
EQUALIZER
P.C.
BOARD
(PCB-3)
REMOVAL
1.
pemove
the
tuner
P.C.
board
(PCB-2).
(Refer
to
step
.)
2,
Remove
8
screws
®
and
then
remove
the
phono
equalizer
P.C.
board
(PCB-3)
with
MC
amp.
P.C.
board
(PCB-4)
and
holder
(198).
At
this
time,
open
the
lid
of
connectors
(P601,
P602,
P603, P604,
P605
and
P801)
on
the
phono
equalizer
P.C.
board
(PCB-3)
and
then
disconnect
the
lead
wires
and
unsolder
the
lead
wires
from
phono
equalizer
P.C,
board
(PCB-3).
CIRCUIT
DESCRIPTION
(1]
MUTING
CIRCUIT
The
muting
control
voltage
is
taken
out
from
(2
pin
of
1C201
and
then
fed
to
the
base
of
0205.
At
the
weak
station
or
detuned
point,
the
2
pin
becomes
high
level,
Q205
becomes
low,
0357
is
tuned
off,
NAND
IC352
is
tuned
to
low,
0360
is
tuned
to
on,
0361
(left
channel)
and
Q362
(right
channel)
are
tuned
to
on
and
muting
operation
is
completed.
[2]
SYNTHESIZER
SECTION
1)
FM
The
output
of
local
oscillator
in
the
front-end
is
fed
to
@®
pin
of
the
pre-scaler
1C701
and
then
divided
by
30
or
32
and
fed
to
@?
pin
of
the
PLL
synthesizer
IC702.
The
standard
quartz
oscillator
output
(4.5MHz)
is
divid-
ed
by
180
in
1C702
and
25kHz
standard
signal
is
got.
The
divided
local
oscillator
output
is
compared
with
the
25kHz
standard
signal
in
the
phase
comparator.
When
the
divided
local
oscillator
frequency
is
higher
than
standard
frequency,
85)
pin
of
1C702
becomes
high
level
but
when
it is
lower,
83)
pin
of
IC702
becomes
low
fevel.
When
the
both
frequencies
are
equal,
@5)
pin
be-
comes
floating.
5)
pin
output
of
1C702
is
fed
to
the
vari-cap
diode
of
the
front-end
through
L.P.F.
(Q702,
Q703,
Q712)
and
controls
the
frequency
of
VCO
(local
oscillator
fre-
quency).
2)
AM
The
local
oscillator
output
of
AM
1C251
is
fed
to
49)
pin
of
the
PLL
synthesizer
1C702
and
divided.
The
standard
quartz
oscillator
output
(4.5MHz)
is
divided
by
450
in
1C702
and
10kHz
standard
signal
is
got.
The
divided
local
oscillator
output
is
compared
with
the
10kHz
standard
signal
in
phase
comparator.
(5)
POWER
OUTPUT
P.C.
BOARD
(PCB-1)
REMOVAL
1.
Remove
the
phono
equalizer
and
MC
amp.
P.C.
boards
(PCB-3
and
PCB-4).
(Refer
to
step
4)
.)
2.
Remove
5
screws
@
and
2
shafts
(242)
and
then
remove
the
power
output
P.C.
board
(PCB-1).
At
this
time,
open
the
lid
of
connector
(P401)
on
the
power
output
P.C.
board
(PCB-1)
and
then
disconnect
the
lead
wires
and
unsolder
the
lead
wires
from
power
output
P.C.
board
(PCB-1).
(G)SPEAKER
SWITCH
AND
SPEAKER
TERMINAL
P.C.
BOARDS
(PCB-11
AND
PCB-12)
REMOVAL
1,
Remove
the
front
panel
assembly
and
power
output
P.C.
board
(PCB-1).
(Refer
to
steps
2)
and
5]
.)
2.
Remove
3
screws
@
and
then
remove
the
panel
back
assembly
(104)
and
the
panel
(140).
3.
Remove
4
screws
©
and
then
remove
the
bracket
(253).
4,
Pull
off
the
2
push
button
assemblies
(109).
5.
Remove
2
screws
@
and
then
remove
the
speaker
switch
and
speaker
terminal
P.C.
boards
(PCB-11
and
PCB-12)
with
bracket
(183).
If
necessary,
un-
solder
the
lead
wires.
TONE
CONTROL
P.C.
BOARD
(PCB-5)
REMOVAL
1.
Remove
the
speaker
switch
and
speaker
terminal
P.C.
boards
(PCB-11
and
PCB-12).
(Refer
to
step
6}
.)
2.
Remove
3
hexagon
nuts
@
and
2
screws
@
and
then
remove
the
tone
control
P.C.
board
(PCB-5).
At
this
time,
open
the
lid
of
connector
(P501)
on
the
tone
control
P.C.
board
(PCB-5)
and
then
disconnect
the
lead
wires
and
unsolder
the
lead
wires
from
tone
control
P.C,
board
(PCB-5).
[3]
PRESET
MEMORY
1)
Memorizing
When
one
of
the
preset
keys,
M1
to
M8
is
depressed,
one
of
the
(2
to
(9
pins
of
1C702
becomes
high
level.
The
displayed
frequency
is
memorized
into
the
memory
(RAM)
with
correspond
to
the
depressed
key.
2)
Recalling
When
one
of
the
preset
keys,
M1
to
M8
is
depressed,
the
contents
of
the
memory
(frequency)
is
recalled.
[4]
FM/AM
STATION
SCANNING
1)
When
tuning
mode
switch
is
set
to
AUTO
When
the
UP
key
is
depressed,
the
frequency
rises
at
saw
tooth
wave
mode
and
when
DOWN
key
is
depressed,
the
frequency
falls.
When
the
high
level
input
is
fed
to
stop
terminal
(
3)
pin
of
[C702),
the
scanning
is
stopped.
2)
When
tuning
mode
switch
is
set
to
MANUAL
Whenever
UP
or
DOWN
key
is
depressed
once,
the
fre-
quency
rises
or
falls
by
one
step
(channel
space).
[5]
OVERLOAD
PROTECTION
(LEFT
CHANNEL)
As
soon
as
the
current
over
rated
power
flows,
the
vol-
tage
between
both
emitters
of
0441
and
0443
rises,
Q9,
Q8
and
Q7
are
turned
to
on,
Q1
is
turned
to
off.
So
Q3
(schmit
trigger
circuit)
is
tuned
to
off.
The
gate
of
0401
becomes
OV
and
0401
is
turned
to
on.
The
input
to
power
amp.
is
cut
and
Q417
is
turned
to
off.
So
the
operation
of
pre-driver,
driver
and
power
stages
stops
and
the
circuit
is
protected.
oo
N

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