Nakamichi 530 User manual

Service
Manual
Nakamichi
Nakamichi
530
Receiver

CONTENTS
1. General «- ete ce cc ee ee te ee eee eee eet eee tee we eet eee eee tee tees 3
2. Principle of Operation - +--+ 0 eee eect eee tt cee ee eee ee ee eet eee rete tee eee 4
2. Fundamental! Circuits «++. 0 eee eee eet eee et ee eee e ee teens Wok gaa oti Seve Ss wae kes 4
BAAS. HONOS AG ok hs bea ated bY Gee. ain ence ag Rundeativa woken esd ante mi wpe indie ira Oe 4
(1) Features of CMOS IC -- eee eee cece ence eee dcp kua tebe ares keke seawake 4
(2) Gate Logic oes erect cece cece eee ee eee ete ee eee eee e tenes 5
(3) Gated Flip-Flop bite Neier eines & seidy yaa BeS, Risen aeres oS ate lo Lesan a Neva eoras aie Taree eta en Cred ORME a ON a ere, ele anueee 5
(4) Compatible CMOS ICs ---+-- esse cece eee eee eee te eee ete teen ees 5
2.1.2 Operational Amplifier IC... - eee eee cece eee eee eee nee teeter eee tees 6
(1) Voltage Follower Circuit --- +--+ e cece ree ec cee ee eee eee eee teen een n eee 6
(2) Amplifier Circuit -- +. eee cee ee nee ee ee cn cere ete ee teen eees 6
(3) Oscillator (Astable Multivibrator) «--- +e e sec e eee cere eee eee renee eee tence 6
(4) Peak Holding Circuit -- + eee eee eee ce eee eee ce eee eee eee rete tenes 7
2.1.3. Quadrature Detector ----- eee crete etcetera eet e eee eee ee tet ee eeee 7
2. 2. Power Mute Signal -+ ++. secre cece cece eee eee te tee ete et eee tee tenes 8
2, 3. TUMEr SECTION: -rs eterna. Speeie te Dw Reales sate eee eye toe Soe ela ele Wow enw Sl eat e 8 Calais arate te ete ysl ORNS “Sue Usa 9
2.3.1.
FM
MPX
Stereo
Broadcasting
Operation
.....---
eee
e
eee
ee
eee
ete
ee
tee
eens
9
2.3.2. Operation of Tuner Section ©... 6c cece ee ete eee teen teen teenies 10
2.3.3. Tuning System 0. ee eee e eee eteeet eee e eee ene eee een tte eee n nee 11
(1) Varicon Voltage ..-- ee ccc cere eee eee tee eet erent eee eee tenes 11
(2) Motor Drive Circuit and Frequency Sensor ...--- +e seer eee eee eee eee eee eee 11
(3) Preset Tuning «++. ee ee eee ee eee ee tee eee tee te ee eee tte 12
(4) Station Detecting Circuit ©... 6... cece cece eee eee te eens 13
(5) Auto-TUning «- eee ccc recente tee eee eee ete eee 13
(6)
Tuning
Indicator...
6.
eee
cece
cece
eee
eee
eee
eee
ene
15
(7) FM Mute and Compulsion Mono «+... +e. eee cece eee eee ete eee e eet n ene 17
9: 9A.'= .Rinplitier SROOM: att sc ¢ tices pes 8G Kee ORE MRE a tec decal ee wedi ead 18
2.4.1. Phono Eq. Amplifier ---- 2-2 ee eee cee te ete ee crete teeter eee 18
2.4.2, Subsonic Filter «6... 22 ccc cece cere c ccc tcc e eee rece nee e eset seen ease eeeeenes 19
2.4.3. Tome Control 2... - 2c ccc cc cece cece c tence eee teen rene erate eee renee enee 20
2.4.4. Power Amplifier... -- 0 eee cece eee eee te ee eer e teen ena 21
(1)
Pre-stage
(Voltage
Amplifier)
..
1.26.0.
e
cece
ce
eee
ee
beeen
teens
21
(2) Output Stage (Power Amplifier) . 2... 00. cece cece ete eee eee eee ees 21
4(3)) CLithiter: <setceatoiee aretting ve a eS Saleh de a EA ee ea Lele ee ae 23
24.5. Protector Circuit «2. 2 cen ee cece cece ee eee eae ened ee een ee eee eee ae en eee 24
3: “Removal Procedures® +«.:/..2 6s :c.c505 eo et ke eee ee eee re eee Sele ewe aa a Ete ead eel ere BUN ene dee ee 25
Ke 1. Top Cover a See eee et ee ar ee ee er a ee eer ee ee ee eR eee ee PC CR Oa Pr Tee Dar Oe Meroe Sa Ma et Dae Ta 25
3.2. Bottom: COVer: acces cc2 5 cera ade eae BN Re hele wha he Aerie a yaad eS jane se aes Bia e Ol Sie a Heese 25
3:3:
Front
Panel
Ass’y
ids
Wane
teas
ec
ek
peietiol
tes
ciao
Vaaen
wa
in
Sue
Oan
tek
Ee
ga
9
25
3. 4. Front-end Holder Ass’y .-- 2 eee cece eee ee cee eee eee eee ete 25
3. 5. Power Transformer... see cece te eee eee eet ee eee ee eee tee eee ee eens 25
3. 6. Diode Bridge --- +. eee eee eee ee eee eee ee ete ete teen teens 25
Ol. CLs Power P.C.B. Ass’y and Heat Sink... .- eee ee eee ee ee eee ete tee ee ete eens 25
3.
8.
Pulley
Holder
B
Ass’y
and
Pulley
Ass’y
«2.
-
eee
cece
eect
erence
ere
rete
eee
e
tenes
25
3. 9. Front Chassis Ass’y -- 20 -e cece cece ee eee re eee eee eee eee teeta ene 25
3. 10. Scale Holder Ass’y - eee eee er cece ee ee eee ete tee ete nee ete neee 25
3. 11. Lamp House Cover Ass’y and Lamp P.C.B. Ass’y -- sees cece eee e eee eee eee eee nee 26
3.
12.
Tuning
Lamp
P.C.B.
Ass’y
+e
eee
e
cece
cere
ene
cere
e
tee
e
eee
eee
eenees
26
3. 13. Indicator P.C.B. Ass’y - +. ee eee cere eee eee eee ete eee ee erence eee tenets 26
3. 14. Tuning Control Switch Ass’y --- 2 eee tee eee eee eee ee ee ee teen eet tee 27
3. 15. | Auto-Tuning P.C.B. Ass’y, Preset Volume P.C.B.
Ass’y and Preset Switch P.C.B. Ass’y +--+ ese etree eee ee eee tenes ee ee 27
3. 16. Power SWitch =. 6622s cee wee ee ec cc eee ee et meee eee eee eee eee eens ede e eens 27
3. 17. Main P.C.B. Ass’y and Function P.C.B. Ass’y «++. eee eee cree eee eee eee eee eens 27
3. 18. Headphone Jack «2... cece eee eee cent ee ee nee teeta teen eens 27
3. 19. Rear Panel Ass’y + eee ee eee eee te eer ee tee ee tee eee eee ete t etter tenes 27

3.
21.
BC
Outlet
ie
5
ois
hee
te
ak
es
SR
ee
Rule
een
ee
eS
wae
eS
Pee
eee
B54
BEE
Sree
are
g
eR
ee
AS
28
3.
22.
Motor
Base
Ass’y,
Front-end
Pulley
and
Front-end
«---
esse
tee
e
creer
eee
eet
eens
28
4.
Adjustments
and
Measurements
----
<0
-
eee
ret
ee
ee
ene
te
eee
tenet
ete
tenets
29
4,
1.
FM
Tuner
Section
--
0.
ee
cece
ree
nee
eee
ett
ee
eee
ee
eee
eee
eee
eee
29
4.1.1.
Electrical
Adjustments
and
Measurements
----
+--+
e
eter
terete
eee
eee
teens
29
4.1.2.
Auto-Return
Scale
Calibration
--
+--+
eee
e
ee
eee eee
eee
eens
da
Rik
tagetaneee
cybiarte
etenshecensiteteaie
8
34
4.
2.
Preamplifier
Section
-----
eee
cette
eee
tect
e
tenet
e
eee
c
eee
eens
34
4.2.1.
Signal-to-Noise
Ratio
Measurement
«+++
ese eee
reece
eee
renee
eee
t
eee
e
eee
eres
34
(1)
Phono
Input/Recording
Output
-----se
eee
reece
tee
eet
tee
eee
eens
34
(2)
Aux.
Input/Preamp.
Output
.--
+--+.
eee
eee
eee
eee
t
eee
eee
e
nents
34
4.2.2.
Distortion
Measurement
.--
eee
cree
eter
ee
ree
ete
ee
ee
eet
tee eee
nen
ete
34
(1).
Phono
Input/Recording
Output
----
+.
eee
cect
nce
eee eee
eee
eee
nee
34
42}
Aux.
Input/Preamp.
Qutput
(<6
+4s
esos
nrews
weeks
node
ease
eh
inet
IN
esos
wee
34
4.2.3.
Phono
Eq.
Amp.
DC
Offset
Adjustment
-----
seer
cere
cree
eee
eee
tenet
e
ene
35
4,
3.
Power
Amplifier
Section
-------
cette
tee
ete
te
teen
tenet
e
nent
nett
ee
eens
35
4.3.1.
Idling
Current
Adjustment
+--+
esses
ee
tee
cece
cee
ete
te
tte
tenet
eee
tents
35
5.
Dial
Threading
and
Scale
Calibration
©.
+--+
+e
ee
ctr
te
ee
eee
ett
teen
teen
eens
36
5.
1.
Dial
Threading
pach
eat
a
eS
th
ae
ny
SY
Nee
OR
ne
|
Be
oes
orca
cca
a
rerea
ie
Aue
Brave
le
Gia,
Use
D
we
letare
exah
gua
aeneay
ee
36
5.1.1.
How
to
prepare
dial
thread
-----
ee
erect
eee
ett
eee
tet
eee
36
5.1.2.
How
to
set
dial
threading
---
+--+
ester
rete
ee te
tee
ett
ee
ene
ete
teen
ete
36
5.
2.
Scale
Calibration
--
000
cece
tee
ee
ee
ee
eee
eee
ee
ete
eee
teeta
eee
36
6.
Mounting
Diagrams
and
Parts
List
-.----
02-2
s
eect
eee
eee
treet
ee
en
teen
ete
n
ea
eee
nee
37
6.
1.
Main
P.C.B.
Ass’y
ee ee
eee
ce
teeter
tee
ete
ee
eet
enter
ee
tte
37
6.
2,
Power
P.C.B.
Ass'y
selidhaa
Vou
ded
Toca
(EP
aon
acto
Boke,
vo
Tote
bh
guta
Roiestinies
eesceieston
WS
Cace
aretlss
See
Grids.
d
oM
eboney
da
eneoatare
re:
ee
39
6
3.
Lamp
P.C.B.
Ass'y
cere
cee
ete
ee
tee
ene
t
eee
ee
eee
en
ete
ee
eee
39
6.
4.
Preset
Switch
P.C.B.
Ass’y
eee
cere
cert
tee
terete
eterna
te
teen
eee
erate
41
6.
5,
Auto-Tuning
P.C.B.
Ass’y
cere
eee
ete
cette
een
n
teen
entre
renee
ete
nets
41
6.
6.
Preset
Volume
P.C.B.
ASS’y
+e
eter
ete
teeter
tee
tence
tate
teen
ene
ene
41
6.
7.
Indicator
P.C.B.
ASS’Y
+
eee
eet
tree
erect
eee
teen
eee
tte
e
seen
esate
41
6.
8
Function
P.C.B,
ASS'Y
cece
ect
rteeereree
eee
ee
ene
tennant
nent
ene
te
ene
ene
41
7.
Mechanism
Ass’y
and
Parts
List
-
+--+.
+e
terete
ee
tet
e
ee
eee
tet
teen
ene
42
7.
1.
SYNTHESIS
«eee
ee
eee
eee
eee
ene
teen
eee
eta
42.
73.
<2,
Front
Panel
Ass’y
(AQ1)
«0
-
see
cece
ete
ee
tere
teen
tenet
ee
eee
e
ene
tenn
es
43
7.
3.
Synthesis
Mechanism
530
(AOQ2)
«sss
ere
t
ttt
terete
ttre
treet
ete
eee
etree
44
7.
4.
Front
Chassis
Ass’y
(BO1)
ser
cece
cre
crc
ete
e
eet
r
ree
teen
ete
e
een
e
tee
e
nen
cnet
es
45
7.
5.
Main
Chassis
Ass’y
(BO2)
-+
++
ec
ect
t
ete
ete
terete
tere
et
eee een
e
cnet
e
eee
tenets
46
7.
6.
Rear
Panel
Ass’'y
(B03)
«sss
ttc
ctr
tt
terre
terete
ete
teen
eet
treet
een
ee
tenes
47
Te Ts
Tuning
Control
Switch
(CO1)
--
errr
errr
ttre
tt
erent
ete
tet
teen
en
cess
48
Y
ee
Scale
Holder
Ass’y
(CO2)
-
secre
reece
etter
te
ttt
ee
ee
eee
ete
49
7.
9.
Power
Block
Ass’y
(DOT)
++
secrete
ttt
etree
teeter
te
ete
e
eee
ete
eaten
een
tees
50
7.
10.
Front-end
Holder
Ass’'y
(DO02)
«s+
eset
etre
tert
teeter
ee
ttre
eee
ens
51
7.11.
Lamp
Case
Ass’'y
(EOI)
sect
cece
rte
teeter
ener
t
teen
enter
eee
nets
51
7.
12.
Lamp
House
Cover
Ass’y
(EO2)
--
+s
sec
c
rrr
etter
rere
r
terete
teeter
tenes
52
7.
13.
Lamp
Base
Ass’y
(EO3)
«s+
reer
rer
cre
ttt
tt
tet
tee
tnt
ete
teeta
e
eee
ene
ees
52
7.
14.
Motor
Base
Ass’y
(FO)
<cre
tere
terete
tee
teen
tet
eee
n
een
n
eee
n
een
entre
52
8.
Block
Diagrams
Sih
Redciimias
ei
eta!
Soe
secie.
Gem
rlonh,
dowrats
seca
fevtocaan
hema
tetas
Brak;
SMA
Oh
Beat
ees
Whe.
Wiens
weld!
eceteniay
ai
teh
tellettay
gal
Tercera:
ietgee
nat
See
53
8.
1.
Tuning
Section
«secre
crete
rete
r
ee
eeeeet
tet
e
en
teeter
eee
e
ects
53
8.
2.
Amplifier
Section
-:
++
+c
scree
eee
tee
eee
eter
t
etn
n
seen
eee
ene
54
9.
Performance
Data
«+--+
-
sce
t
eee
cette
teen
ee
ener
te
teen
ee
eet
ee
55
9.
4.
Tuner
Section
«sere
ere
ee
tt
tee
ete
eee
nee
ene
eee
eet
e
eater
eae
ee
see?
55
9.
2.
Amplifier
Sections:
+e
treet
errr
teen
tenet
entree
etn
e
tenant
este
en
nent
55
10.
Schematic
Diagram
Basin
bs
etd
he
Teco?
6
Resse
bP
aa
es
pre
BSN
cee!
ain
See
w
eie
a
cote
Let
pe
Gace
Sy
a
ene
B.S
sree
tan
ernie
Te
Ge
te
ees
a
ae
55
V1.
Wiring
Diagram
«+++
-
0
ee
eee
eee
eee
eee
ees
bh,
Jetset
ou
cate
iuwatd
saebetacin
dy
thcevd
bch
tne
ce
eto
acer
es
57
12,
Specifications
---
++
ce
eet
eee
tet
ee
tte
een
ete
e
eee
ert
e
eae
tere
ee
ete
58
3.
20.
12P
Jack,
Speaker
Terminal
and
Antenna
Terminal
-
+--+.
sees
cere
eter
ee
eee
tren
ee
eens
27

1. GENERAL
Nakamichi 530 control functions are shown below:
Pe
Totss 150 Watts Max,
8) 64
on ) ONoOkANnNr-oo
ONAaAPWN>
Nakamichi 530
Receiver -Mopet No. $30
Voltages 120V ~
‘Unit Pewer
‘AC Outlets Total
Subsonic Filter Switch
Mono Switch
Loudness Switch
Audio Mute Switch
FM Mute Switch
Hi-Blend Switch
Threshold Selector Switch
Tuning Pointer
Tuning !ndicators
. Tuning Scale
. Stereo Indicator
FM Muting Indicator
. Power Switch
. Speaker Selector Switches
. Station Preset Controls
. Automatic Scanning Switches
. Station Memory Switches
Volume Control
@) &@ 9)
Antenne
3000tm Bai. 7EohmUnbel.
SCenenriios ys Ve ey ae
‘3bOWatte Max. ate he be
~ wey
gH
63) 62)
102 104 106
tebe tr tbs te dad
Fig. 1.1 Front View
Fig. 1.2 Rear View
Spaskars:
(tenet
@eo O16
A 4 ; A
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
© Ben anie
69) @9 Moe e4)
Balance Control
Tone Controls (Bass, Treble)
Tape Monitor Switch
Function Selector Switches
(Aux/FM/Phono)
Headphone Jack
Ground Terminal
Phono Input Jacks
Auxiliary Input Jacks
Tape Playback Input Jacks
Tape Recording Output Jacks
Preamplifier Output Jacks
Main Amplifier Input Jacks
Speaker Output Terminals (A & B)
75-ohm Unbalanced Terminals
300-ohm Balanced Terminals
AC Outlets
AC Power Cord

2.
PRINCIPLE
OF
OPERATION
2.1. Fundamental Circuits
2.1.1.
C-MOS
IC
(1) Features of C-MOS IC
The
IC’s
used
in
the
logic
circuit
of
the
N-530
are
of
the
C-MOS
{complementary
metal
oxide
semiconductor)
type,
in
which
P-channel
and
N-channel!
MOS
FET’s
complement
each
other.
(a)
Small
power
consumption
A
C-MOS
is
an
inverter,
as
shown
in
Fig.
2.1.1.
Whether
the
input
of
this
inverter
is
at
H
or
L
level,
either
the
P-channel
or
N-channel
MOS
FET
is
OFF,
and
therefore,
current
does
not
pass
from
VDD
to
VSS
under
steady
normal
state.
Consequently,
when
there
is
no
input,
power
consumption
(VDD
x
!DD)
is
nearly
zero,
except
for
surface
and
junction
leakage.
When
the
input
signal
is
switched
from
H
to
L,
or
Lto
H,
however,
both
P-
and
N-channel
FET’s
instantly
come
on,
and
a
current
flows
either
charging
or
discharging
the
stray
output
capacity,
so
that
the
power
consumption
during
dynamic
operation
cannot
be
said
to
be
zero.
(b) A large noise margin
The
input-output
transmission
characteristics
of
the
C-MOS
inverter
differ
from
those
of
bipolar
IC's
as
shown
in
Fig.
2.1.2.
The
knee
characteristic
is
sharper,
the
threshold
voltage
is
almost
half
of
VDD,
and
the
output
amplitude
is
nearly
equal
to
VDD
—
vss.
Since
the
noise
margin
of
a
digital
IC
is
defined
as
the
difference
between
the
minimum
value
of
output
amplitude
and
the
required
minimum
amplitude
of
the
input
signal,
it
is
quite
natural
that
the
C-MOS
circuit,
which
produces
an
output
amplitude
of
nearly
VDD
—
VSS
and
should
be
operated
by
a
small
input
signal,
should
have
a
large
noise
margin.
(c) High input impedance
A
C-MOS
IC
has
a
very
high
input
impedance
because
it
is
insulated
from
the
substrate
by
the
oxide
film
of
the
gate.
Although
leakage
resistance
must
be
considered
in
an
actual
C-MOS
IC
because
diodes
are
usually
used
in
the
direction
of
reverse
bias
for
protecting
input
circuit,
its
impedance
is
several
tens
of
megohms.
The
advantage
of
a
high
input
impedance
is
that
the
fan-out
of
the
IC
is
large,
which
simplifies
the
interface.
Also,
a
timer
circuit
for
a
longer
‘period
of
time
can
be
produced.
This
means
that
the
high
input
impedance
enables
the
input
to
be
connected
with
a
large
resistance,
but
does
not
mean
to
use
a
capacitor
of
large
capacity.
(d)
Wide
operating
voltage
range
Fig.
2.1.3
shows
input-output
transfer
characteristics
of
C-MOS.
The
general
purpose
C-MOS
family
has
a
wide
operating
voltage
range
extending
from
3
to
18V,
which
is
much
wider
than
that
of
TTL
and
DTL
(5+
0.25
V),
and
HTL
(15
+
1.5
V).
The
reason
for
the
C-MOS
IC’s
wide
operating
voltage
range
is
that
the
P-MOS
and
N-MOS
are
made
symmetrical,
and
if
VDD
is
varied,
the
threshold
voltage
for
the
circuit
is
always
about
half
of
VDD.
Ina
bipolar
IC,
the
threshold
voltage
is
decided
by
the
forward
voltage
from
the
base
to
the
emitter
of
the
transistor
(VBE),
and
is
little
affected
by
the
source
voltage.
Therefore,
if
the
source
voltage
exceeds
a
certain
limit,
the
output
voltage
and
the
threshold
voltage
will
not
balance,
as
a
result
of
which
operation
will
become
impossible.
With
a
C-MOS,
the
threshold
voltage
varies
according
to
changes
in
the
source
voltage,
and
stable
operation
throughout
a
wide
range
can
be
expected.
As
indicated
above,
the
performance
of
a
C-MOS
IC
as
a
digital
IC
is
excellent.
VoD
P-channel
MOS FET
Output
N-channel
MOS FET
o
Fig.
2.1.1
C-MOS
Inverter
a -#
a oO
Ny
OUTPUT VOLTAGE (V)
4
2
3
4
5
6
INPUT VOLTAGE(V)
°
Fig.
2.1.2
Input-Output
Transmission
Characteristics
< =
Oo oO
OUTPUT VOLTAGE (V)
oO
ie)
5
10
415
INPUT
VOLTAGE
(V)
Fig.
2.1.3
Input-Output
Transfer
Characteristics
of
C-MOS
(The
threshold
voltage
is
approxi-
mately
half
of
VDD.)

(2) Gate Logic
2-input NAND gate is used.
Following show each of logic symbol, truth table, pin
assignment, and internal schematic diagram.
The output will be L only if inputs IN1 and IN2 are H’s,
and the output will be H if IN1 is L or IN2 is L.
Out
IN2
Out = INT-IN2-
IN 1
IN 2 ia
Out = INT + IND ng _
Out = INT-IN2 = INT + IN2
Fig. 2.1.4
Truth Table 1
The construction of the foregoing 2 Logic Symbols is
identical and intended to show the use of either AND or
OR.
(3) Gated Filp-Flop
The two NAND gates can be used to form flip-flop.
The inputs operate as follows:
When both S and R are H’s, the flip-flop will remain in its
present state, i.e., will not change the state.
If however, the R input goes to L, the NAND gate
connected to R will have H output regardless of the other
feedback input to the NAND gate, and this will force the
flip-flop to the L state {provided the S input is kept H).
Similar reasoning shows that making the S input an L will
cause the NAND gate at the S input to have an H output,
forcing the flip-flop to the H state (again provided the R
input is kept H).
If both inputs R and S are made L’s, the next state will
depend on which input is returned to H first, and if both
are returned to H simultaneously, the resulting state of
the filp-flop will be indeterminate. As a result, this is a
“forbidden” or “restricted” input combination.
(4) Compatible C-MOS ICs
1C306: ywPD4011C, CD4011A, MC14011A,
F34011A, TP4011A, TC4011P
Vop A4 B4 Y4 Y3 A3 B3
Ai B1
Set (s)
Reset (Rr)
Yi Y2 Az B2 GND
(TOP VIEW)
Fig. 2.1.5
VoD
GND
Fig. 2.1.6
Q
Q
Fig. 2.1.7
Truth Table 2
*: Maintains the previous state.

2.1.2.
Operational
Amplifier
IC
Most
operational
amplifier
IC‘s
consist
of
a
differential
amplifier
with
a
voltage
amplification
of
70
to
100
dB.
High-gain
amplifier
circuits,
oscillators
or
comparators
use
operational
amplifier
IC.
(Vin — Vin (—)) x Av = Vout
Vin
Vout
Vin(-)
Gain=Av
Fig.
2.1.8
Operational
Amplifier
(1) Voltage follower circuit
This
circuit
is
a
special-purpose
non-inverting
amplifier.
It
is
used
for
converting
impedance
when
the
impedance
of
the
input
signal
source
is
too
high
and
the
input
impedance
of
the
following
step
is
too
low
for
direct
connection.
The
special
feature
of
the
voltage
follower
is
high
input
impedance
and low
output
impedance.
Its
voltage
gain
is
1.
(Vin — Vout) x Av = Vout
Vout
_
a,
Au
+
Vout
=
Vout
(1
+)
=
Vout
Vin
Vin =
Vout
Fig. 2.1.9 Voltage Follower Circuit
(2) Amplifier circuit
Two
types
of
amplifier
circuits
are
the
inverting
amplifier
and
the
non-inverting
amplifer.
The
amplification
factor
R, + Ro
Ra :
Inverting
circuits
output
signals
of
phases
opposite
to
those of the input signals.
of these circuits is
: R2 =
(Vin — Vout Ri + R,) x Av = Vout
:
Vout
R,
=———— + —_—
Vin Ay Vout R, +R,
1 R,
=
V
—._
++
+
ue tA R; + R2
Es Re by ab os
= Vout Ry Re Ge Ay = 0)
Vout = Vin Ri + Ro
Ro
Vout
Fig.
2.1.10
Non-inverting
Fig.
2.1.11
Inverting
(3)
Oscillator
(Astable
Multivibrator)
The
operational
amplifier amplifies
the
difference
be-
tween
non-inverting
input
and
inverting
input,
and
gen-
erally
its
output
is
amplified
up
to
the
source
voltage
because
of
the
high
voltage
amplification.
in
the
circuit
shown
in
Fig.
2.1.12.,
Vout
equals
the
positive
source
voltage
when
the
non-inverting
input
is
larger
than
the
inverting
input.
The
voltage
of
the
non-inverting
input
is
R
of
the
positive
source
2
2
+ R3
voltage.
On
the
other
hand,
because
C1
is
charged
by
the
Vout
voltage
through
R1,
the
inverting
input
rises
to
the
positive
source
voltage.
However,
when
it
exceeds
the
voltage
of
the
non-inverting
input,
Vout
is
inverted
to
the
negative
source
voltage.
The
voltage
of
the
non-inverting
sal
ae
of
the
negative
source
voltage.
When
C,
is
discharged
through
R;
and
the
voltage
of
the
inverting
input
becomes
lower
than
that
of
the
non-
inverting
input,
Vout
is
again
inverted
to
the
positive
source
voltage.
By
repeating
these
operations,
the
circuit
acts
as
an
astable
multivibrator.
See
Fig.
2.1.13
timing
chart.
input then is
2R2
T = 2C; Ri 2n(1 + ) [sec.]
R3
Fig. 2.1.12 Oscillator
R2
Inverting
R2+R3
Input
R
2
—VRZ+RS
R2
+Va55RF
Non
-Inverting
R2+R3
Input
R2
—VR2+R3
+V
V out
—V
Fig. 2.1.13 Timing Chart

(4) Peak holding circuit ;
Figs.
2.1.14.
and
2.1.15.
show
the
peak
holding
circuit
for
Input
Output
positive
input
voltage
and
its
timing
chart.
This
circuit
holds
the
peak
value
of
the
input
voltage.
R]c
When
the
input
signals
are
pulses,
the
capacitor
C
ng
repeatedly
charges
and
dischages
to
hold
the
peak
value.
:
:
When
no
pulse
is
supplied,
C
is
discharged
through
R
and
Fig.
2.1.14
Peak
Holding
Circuit
the output becomes O with a certain time constant. It is
used in the N-530 in combination with an oscillator for
frequency-voltage
conversion.
A
J
Tc
{Input
t
E-e CR
Output E
Fig. 2.1.15 Timing Chart
2.1.3.
Quadrature
Detector
is
supplied
to
another.
The
pulse
width
of
output
iL
varies
Figs.
2.1.16.-2.1.18.
show
the
structure
and
operation
according
to
the
phase
difference
between
the
direct
input
principle
of
the
quadrature
detector.
It
is
a
phase
detector
e,
and
the
input
through
the
phase
shifter
e2
and
phase
in
which
a
direct
signal
is
supplied
to
an
input
terminal
of
detection
is
made
by
the
increase
and
decrease
of
the
the
multiplier,
and
a
signal
through
a
90°
phase
shifter
mean
value
iav.
90°t AD Multiplier P
Phase
(chadearere)
me
eal
©
Output
Shifter
Detector
Go
Audio
Preamp,
Input Limiting
Amp,
Cin
Fig. 2.1.16 Quadrature Detector System Diagram
I
Shifter
.
90°t
40
it
{
i2
€2 0
i average
Fig. 2.1.17 Quadrature Detector Circuit i |
Fig. 2.1.18 Timing Chart

2.2. Power Mute Signal -
Refer to the timing chart in Fig. 2.2.1. and circuit
diagram in Fig. 2.2.2.
(1) Power ON
When the Power Switch is pressed to power ON, +12V,
+40V and +18V Power Source will be supplied.
In the meantime, when Q306 is turned OFF, C309
(33 uF 25 V) will be charged via R314 (1 MQ), then
0307 will be turned ON approx. 2 seconds later to
release the Power Mute Signal. In other words the said
Power Mute Signal will bring the N-530 in Mute condition
approx. 2 seconds after the Power Switch is pressed ON.
Power Mute = L will enter the Preout Mute Circuit (0107
and 0207) and Auto Tuning flip-flops of the Main P.C.B.,
and mutes each output terminal and resets each flip-flop.
It is also supplied to the Relay RL301 to turn OFF and
opens the supply to Speaker System.
When Power Mute Signal is released, the Relay RL301
becomes turned ON and Speaker System will be con-
nected,
(2) Power OFF
When the Power Switch is released to power OFF, +12V,
+40V and +18V will no longer be supplied, Q306 is
turned ON during discharge of C308 (47 uF 25 V) via
0304 and R313 (2.2 MQ). When O306 is turned ON,
C309 will immediately be discharged via Q306. This way
Q307 and Q308 will be turned OFF, Power Mute = L
will be supplied to the Main P.C.B.
1C304
pA7B42M
D302
Q304
2SA733
R306 3.3K
R308 400K
fe)
C307 2200 25v
R307 40K
R309 400K
DC Voltage Detector Abnormal Temperature Detector
Power
Switch
+42V
t4ov
48V
Q304
Q306
C309
Q307
Q308
Power Mute
Q306
280945
ON
OFF
ON
OFF
ON
OFF
ON
OFF
OV
ON
OFF
H
L
Fig.
R314 4M
C309 33y 25V(LN)
2.2.1 Power Mute Timing Chart
Q307
28$€1400
2SA750 (4)
© Power Mute
R347 40K
—18V
Fig. 2.2.2 Power Mute Generating Circuit

2.3. Tuner Section
2.3.1. FM MPX Stereo Broadcasting Operation
As is generally known, the amplitude of the carrier wave is
modulated in AM broadcasting whereas the carrier fre-
quency is modulated in FM broadcasting. Fig. 2.3.1.
illustrates these conditions.
FM transmitters and receivers, although considerably
more complicated than those for AM broadcasting, permit
radio reception with very high fidelity and any difference
in technical skill will be noticeably manifested in the
performance of the equipment. Compared to AM broad-
casting, FM broadcasting has many advantages, such as
better frequency response, higher S/N ratio, less inter-
ference, less distortion, etc. However, its greatest advan-
tage is the capability for compatible stereo broadcasting.
This is achieved by employing a composite signal, as
shown in “4” of Fig. 2.3.2. instead of the audio signal
shown in Fig. 2.3.1.
Since the composite signals transmitted in ordinary
broadcasting have an extremely complex waveform, it is
hard to recognize them, even when observed with an
oscilloscope. Figure 2.3.2. illustrates an L channel signal
of 1900 Hz with no R channel signal.
As shown in “1” of Fig. 2.3.2., this is a stereo signal
modulated so as to swing at 38 kHz between the L
channel signal and R channel signal.
Therefore, this signal can be separated into L ch/R ch, by
a synchronizing signal with the 38 kHz of the stereo signal
and a circuit which is conducting at the positive peak and
negative peak of this synchronizing signals; the L ch/R ch
signals will come out separately.
But, as is shown by the signal waveform “1” in Fig. 2.3.2.,
since the phase at 38 kHz is reversed between the positive
and negative half-cycles of the L ch signal, even with the
separation described above, it is not possible to distinguish
L ch from R ch.
Audio
Signal
Carrier
Noise mixes
Under these conditions, it is possible that the L ch/R ch is
reversed each time the power switch is turned ON/OFF,
Here lies the importance of the pilot signal. That is, when
making the 38 kHz signal (’’3” in Fig. 2.3.2) by doubling
the 19 kHz pilot signal, if the positive and negative peaks
of the 19 kHz wave are synchronized with a negative peak
at the 38 kHz, L channel can be taken out at the positive
peak of the 38 kHz signal and the R channel! at the
L-Signal Envelope
R~Signal Envelope
Stereo Signal
Modulated
at 38 kHz
L-Signal 1900Hz
R-Signal O
Ole rial | CRU OU h Ua CAC VAC AUAY
19 kHz
@ 38 kHz
® Composite
Signal
Fig. 2.3.2 MPX Stereo Signal
Signal
demodulated
Limiter
unusable
>
Cut by limiter
aa ave
rac ae
Fig. 2.3.1 AM and FM

negative
peak.
Thus,
MPX
stereo
signals
are
broadcast
ina
waveform
such
as
composite
signal
‘“4,
obtained
by
combining
the
pilot
signal
2’
with
the
stereo
signal
‘1’
in
Fig.
2.3.2.
In
order
to
divide
the
FM
signal
into
the
left
and
right
channels,
the
MPX
stage
of
an
FM
tuner
must
synch-
ronize
the
multiplex
signal
with
the
19
kHz
pilot
signal.
lf
this
synchronization
is
not
properly
performed,
stereo
separation
will
be
poor.
2.3.2. Operation of Tuner Section
Fig.
2.3.3.
shows
a
block
diagram
of
the
N-530
tuner
section.
The
input
from
an
antenna
which
first
enters
the
radio
frequency
unit
(front-end),
is
amplified
in
a
tuning
circuit,
and
mixed
with
a
local
oscillator
frequency,
and
an
intermediate
frequency
(IF
10.7
MHz)
is
produced.
Since
the
radio
Frequency
is
high
and
it
is
impossible
to
obtain
stable
amplification
and
sufficient
separation,
it
is
converted
to
an
easy-to-handle
10.7
MHz.
Conversion
of
IF
is
made
to
improve
these
characteristics.
Frequency
conversion
makes
use
of
the
fact
that
when
two
different
frequencies
are
mixed
and
detected,
a
frequency
component
equal
to
the
difference
between
the
two
frequencies
is
generated.
Since
radio
frequencies
vary
according
to
the
choice
of
the
station,
the
tuning
circuit
must
be
adjustable.
However,
the
use
of
an
intermediate
frequency
fixed
at
10.7
MHz
makes
it
possible
to
achieve
optimum
tuning
characteristics
with
a
multi-stage
tuning
circuit
(3-stages
in
the
N-530)
and
sharp
separation
with
two
ceramic
filters.
Also,
the
function
of
a
limiter
to
remove
extraneous
noise,
as
usual
in
an
intermediate
frequency
unit,
requires
a
sufficiently
high-degree
of
amplification
(130dB
or
more
in
the
N-530)
to
improve
limiter
characteristics.
For
this
purpose
and
to
prevent
instability
due
to
output
feedback
to
the
input
side,
an
adequate
shield
must
be
provided
and
the
component
parts
must
be
carefully
arranged.
The
time
required
for
a
signal
applied
to
the
input
of
an
intermediate
frequency
unit
to
emerge
from
the
output
generally
varies
according
to
frequency.
in
an
ordinary
broadcasting,
since
the
frequency
varies
in
a
range
of
10.7
MHz
+
75
kHz,
a
frequency
with
a
shorter
transit
time
catches
up
with
the
preceding
signal
before
emerging
as
output.
This
will
result
in
a
high
frequency.
Also,
an
interval
will
be
opened
between
a
slow
signal
and
the
preceding
signal
which
produces
a
lower
frequency.
This
kind
of
variation
in
the
transit
time
occurs
mainly
in
the
tuning
circuit,
resulting
in
increased
distortion.
This
is
called
group
delay
characteristic
and
one
of
the
important
features
of
an
intermediate
frequen-
cy
unit,
In
the
N-530,
superior
selectivity
and
group
delay
characteristics
have
been
realized
by
employing
a
4-
element
and
a
2-element
Ceramic
Filters,
1F
Amp.
using
an
1C302
pPC1167C
and
Quadrature
Detector
(refer
to
item
2.1.3).
The
composite
signal
is
taken
out
by
demodulating
the
10
FM
signal
with
a
Quadrature
Detector,
1C302
uPC1167C,
in
the
intermediate
frequency
unit.
Linearity
of
the
discriminator
is
very
important,
and
must
be
regulated
with
adequate
care
since
poor
linearity
will
result
in
increasing
distortion
and
poor
channel
separa-
tion.
Good
Quadrature
Detector
characteristics
are
shown
in
Fig.
2.3.4.
by
the
solid
line,
where
the
output
voltage
varies
in
a
straight
line
over
the
+100
kHz
range
and
voltage
is
5
V
DC
at
the
center
frequency.
If,
as
shown
by
the
dotted
line,
there
is
asymmetry
above
and
below,
the
voltage
is
not
5
V
DC
at
the
center
frequency,
and
the
degree
of
distortion
will
increase.
The
discriminator
of
the
N-530
has
a
broad
linear
zone
(£200
kHz
or
more).
As
the
Self-Locked
Tuning
of
the
N-530
will
operate
approximately
7
seconds
after
the
tuning,
FM
broadcast-receiving
can
be
performed
under
the
distortion
free
condition
at
all
times.
The
discriminator
output
is
applied
to
the
PLL
(phase
er ee
D310 R394
44—_Ww
locked
loop)
IC,
uPC1161C
in
the
MPX
unit.
The
38
kHz
signal
which
is
synchronous
with
the
19
kHz
involved
in
the
composite
signa!
is
produced
in
MPX
unit.
This
leads
to
separate
the
L
channel
and
R
channel
signals
(reler
to
Fig.
2.3.2).
Therefore,
in
order
to
achieve
good
channel
separation,
the
high
end
and
low end
of
the
38kHz
waveform
must
be
symmetrical
and
the
phase
must
be
precisely
aligned.
In
the
N-530,
good
channel
separation
has
been
realized
by
means
of
a
stabilized
synchronizing
signal
obtained
by
a
PLL
IC.
With
this,
even
if
an
SCA
(Subsidiary
Communication
Authorization)
signal
is
present,
no
beat
interference
can
occur.
Tojobtain
a
good
S/N
ratio,
pre-emphasis
is
made
on
the
transmitter
side
and
de-emphasis
is
made
on
the
receiver
side.
The
time
constant
of
75
us
is
mainly
employed
by
the
U.S.A.
and.
Canada,
and
50
us
in
Europe
and
other
countries
including
Japan.
Although
the
19
kHz
pilot
signal
is
especially
difficult
to
LPF,
1F Amp, , Limiter
‘ond Oiscri,
(SkH2)
tO
/ FM Mute
HPF,
{
remove
because
of
its
proximity
to
the
audio
signal,
the
N-530
uses
a
specially-designed
low-pass
filter
to
achieve
an
attenuation
characteristic
of
40
dB
or
more
for
the
19
kHz
signal,
while
keeping
flat
frequency
response
up
to
15 kHz.
Good Characteristics j
Output Voltage
: | “Poor Characteristics
7 anil
10.6 10.7 10.8
Frequency (MHz)
Fig.
2.3.4
Discriminator
Characteristics
(S-Curve)
FM Ourput
(30H2)
O Reh
FM Mute
4
Auto
Tuning
R363 Stereo
—ANv
0328
~
|
@® Rewrn Signot
“itt {ft 0
LL | mute our fs3> ” = {o313)
0323
C339
R353
343
Preset Trigger
Reset
Compulsion Mono
+412V
—o Power Mute
i
Se
ES
LS
ES
Fig.
2.3.3
FM
Tuner
System
Diagram
i

2.3.3. Tuning System
(1) Varicon Voltage
Refer to Figs. 2.3.5. and 2.3.6., circuit diagram and timing
chart. Generates the DC voltage (Varicon Voltage) corres-
ponding to the capacity of varicon by means of AM
varicon of the Front-end. The DC voltage is in an inverse
proportion to the varicon capacity, wherein when
capacity is increased, voltage will become decreased. As
the varicon capacity corresponds to the tuning frequency,
the said Varicon Voltage will become to correspond to the
tuning frequency. The variable voltage range of preset
tuning, and minimum and maximum range in which the
auto-return is activated is also established within this
Varicon Voltage range.
1C304-(1/2) of the Main P.C.B. forms an astable multi-
vibrator and oscillates square wave of approx. 2.38 kHz.
This oscillation output will enter variable integral circuit
(becomes variable according to variation of varicon
capacity). The integrated signals will enter the plus Peak
Hold circuit consisting of IC304-(2/2) and will be convert-
ed to DC voltage in inverse proportion to the varicon
capacity.
+412V +42v +42v |
Oo oO Oo
R326 220K !
R325 220K
x
O°
as
a)
m
a
OK
R328 401 AM
Varicon
C336 420P{J}
R324 220K
C334
39C0P{U)
“R330 2.2K
Varicon
I
Voltage |
|
R332 820K
R333 1M
(Main P.C.B)
Fig. 2.3.5 Varicon Voltage Generating Circuit
Approx,
1C304-4
Q302 4 a / | f |
Collector
Varicon Pas a gor
Voltage — been eye als BE sere f IES
Fig. 2.3.6 Timing Chart
(2) Motor Drive Circuit and Frequency Sensor
Refer to Fig. 2.3.7, circuit diagram.
Tuning Motor of the N-530 drives Front-end. Tuning
Motor Drive Circuit consists of 1C307(2/2), 0303, 0304,
Q305, Q308, 0309, etc. 1C307(2/2) forms a comparison
circuit, and by switching Auto/Preset Switch, comparison
of AFC Voltage and REF Voltage in auto-tuning mode; or
Varicon Voltage and Preset Voltage in preset mode will
be performed. Auto/Preset Switch is one of the 5-Way
Switch incorporated in the Preset Switch P.C.B. Ass’y and
this switch is interlocked with Automatic Scanning
Switches and Station Memory Switches A — D. Tuning
Motor will be driven by O309 and 0305, or 0304 and
Q308. Q303 is an inverter to invert the polarity of
1C307-7(2/2) output.
When the difference between both IC307(2/2) inputs
becomes nil, i.e, both input levels are equal, Tuning
Motor will stop.
Frequency Sensor Circuit consists of D304, D305, 0306
and Q307, and D304 will be turned ON when 0309 and
Q305 are turned ON and D305 will be turned ON when
Q304 and 0308 are turned ON.
D304 and D305 from a wired-OR circuit, and while
Tuning Motor is driven, either one diode will be turned
ON, thus the output of wired-OR become H. Namely, this
circuit detects while motor is driven. When the output
voltage of the wired-OR exceeds REF Voltage, 0306 will
be turned ON and Q307 will be turned ON. When Tuning
Motor is in stop mode, D304 and D305 will be turned
OFF, as a result the base voltage of Q306 will become the
same voltage as emitter (REF Voltage), accordingly 0306
will be turned OFF and Q307 will also be turned OFF.
The collector voltage of Q307 will become approx. +12 V
when Frequency Sensor is activated, but will become
GND level when it does not function.
(a) Preset Tuning
By pressing Station Memory Switch A, B, C, or D, the said
Auto/Preset Switch is released and preset tuning mode is
selected. As a result, Preset Voltage is given to
1C©307-5(2/2) and Varicon Voltage is fed to |C307-6(2/2).
Tuning Motor will be driven until the difference between
the above inputs to 1C307(2/2) becomes nil. When the
difference becomes zero, i.e., when Varicon Voltage
becomes equal to Preset Voltage, Tuning Motor will stop
its rotation and stay at that station.
From this condition, when you turn Station Preset
Control manually, a difference of the input levels will
occur as the voltage at 1C307-5(2/2) changes. As a result,
Tuning Motor starts rotation and then stops at the station
where the difference of the input levels becomes zero.
(b) Auto-tuning
Auto/Preset Switch is changed to auto-tuning side by
pressing Automatic Scanning Switch Left or Right,
therefore, REF Voltage is given to 1C307-5(2/2) and AFC
Voltage is fed to 1C307-6(2/2).
Meanwhile, when Automatic Scanning Switch Left is
pressed, Auto LT Flip-Flop of the Main P.C.B. Ass’y is
set, as a result D309 is turned ON and 1C307-5(2/2) is
grounded through R390, therefore, both input voltages of
1C307(2/2) will become imbalanced. As a result, 0308
will be turned ON and 0303 will be turned OFF, and
Q304 will be turned ON. Accordingly Tuning Motor will
be driven to the direction that the receiving frequency is
decreased. When a station is detected, Reset Pulse is
generated and Auto LT Flip-Flop is reset and D309 is
turned OFF. As a result, REF Voltage and AFC Voltage
are applied to 1C307(2/2), and when these voltages
become equal, Tuning Motor will stop. If no station is
found in the left hand frequency band, Tuning Motor will
continue driving until it reaches Minus Return Point.
At 1C305(1/2), Minus Return Signal and Varicon Voltage
are compared, and when Varicon Voltage exceeds Minus
Return Signal, Auto LT Flip-Flop is reset and Auto RT
Flip-Flop is set. Therefore, Tuning Motor will change its
direction and moves to the right hand frequency band,
and then stops if a new station is detected.
On the other hand, when Automatic Scanning Switch
Right is pressed, Auto RT Flip-Flop of the Main P.C.B.
Ass’'y is set, as a result D310 is turned ON and
1C307-6(2/2) is grounded through R391, therefore, both
input voltages of 1C307(2/2) will become imbalanced.
Thus, 0309 will be turned ON and 0303 will be turned
ON, and Q305 will be turned ON. Accordingly Tuning
Motor will be driven to the direction that the receiving
frequency is increased.
When a station is detected, Reset Pulse is generated and
Auto RT Flip-Flop is reset and D310 is turned OFF. Asa
result, REF Voltage and AFC Voltage are applied to
1C307(2/2), and when these voltages become equal,
Tuning Motor will stop. If no station is found in the right
hand frequency band, Tuning Motor will continue driving
R337 2.2M
Auto/ Preset
Switch
Auto
until it reaches Plus Return Point. At 1C305(2/2), Plus
Return Signal and Varicon Voltage are compared, and
when Varicon Voltage exceeds Plus Return Signal, Auto
RT Flip-Flop is reset and Auto LT Flip-Flop is set. Thus,
Tuning Motor will change its direction and moves to the
left hand frequency band, and when a new station is
detected, Tuning Motor will stop.
(c)
Frequency
Sensor
(Detector
while
Motor
Drive)
and
AFC
Control
While
Tuning
Motor
is
driving,
Frequency
Sensor
Output
(cathode
of
D304
and
D305)
will
become
H.
Since
this
H
level
is
higher
than
REF
Voltage,
Q306
and
0307
will
be
turned
ON.
On
the
other
hand,
when
Tuning
Motor
is
in
stop
mode,
D304
and
D305
are
turned
OFF,
as
a
result
the
base
voltage
of
Q306
becomes
the
same
voltage
as
emitter
(REF
Voltage),
therefore
0306
and
0307
will
be
turned
OFF.
Collector
output
of
Q307
is
given
to
IF
section
as AFC
Control
Signal
and
controls
ON/OFF
of
AFC
function.
When
0307
is
turned
ON,
D302
is
turned
ON
and
+12
V
is
applied
to
AFC
Control
Circuit.
As
a
result,
D301
is
turned
OFF
and
Q301
is
turned
ON,
therefore
AFC
function
is
not
activated
as
AFC
Voltage
and
REF
Voltage
become
equal.
On
the
other
hand,
when
Q307
is
turned
OFF,
D302
is
turned
OFF,
and
then
D301
is
turned
ON
when
C320
finished
discharge.
As
a
result,
Q301
is
turned
OFF
and
the
shorting
between
AFC
Voltage
and
REF
Voltage
through
0301
is
released,
thus
AFC
is
activated.
Further,
when
Q307
is
turned
ON,
0318
is
turned
ON,
and
Q319
and
0317
are
turned
ON.
As
a
result,
Q319
will
illuminate
FM
Mute
Lamp
and
0317
will
turn
ON
Q103
and
Q203
resulting
in
muting
FM
Outputs.
When
Q307
is
turned
OFF,
0318
is
turned
OFF,
and
after
discharge
of
C340
is
finished,
Q319
and
0317
will
be
turned
OFF.
Accordingly,
in
this
condition,
FM
Mute
Lamp
will
go
out
and
mute
of
FM
Outputs
will
be
released.
o
w to)
S
3 AW. )
R344 680
R323 42K
REF © R335 6.8K Tuning Motor
Preset Voltage Os—=7O | R336 6.8K 1@) 4
:
Q303
arc
Q-Aule
Q305
Varicon Voltage Oscar O ae
R338 2.2M
R396 100K C348 0.04p
Preset Trigger Q—»——
AWW
R347 40K
R344
400K
Q306
© AFC Control
© REF
R340 330K
© Mute Generator
Fig. 2.3.7. Motor Drive Circuit and Frequency Sensor Circuit
11

(3)
Preset
Tuning
Fig.
2.3.8
shows
the
range
of
preset
variable
voltage
while
preset
tuning,
and
the
voltage
of
Plus
Return
Signal
and
Minus
Return
Signal
for
the
auto-return
while
auto-
tuning.
Fig.
2.3.9
shows
its
circuit
diagram.
Press-command
either
A,
B,
C,
or
D
of
the
Station
Memory
Sensors
will
automatically
select
the
preset
station.
The
N-530
incorporates
Auto/Preset
Switch.
This
switch
is
interlocked
with
Automatic
Scanning
Switches
and
Station
Memory
Switches
A
—
D,
and
it
will
select
auto-tuning
mode
if
Automatic
Scanning
Switch
is
pressed,
and
preset
tuning
mode
if
Station
Memory
Switch
is
pressed.
This
switch
will
not
change
its
state
unless
other
tuning
mode
is
commanded.
When
Station
Memory
Switch
A
is
pressed,
while
in
auto-tuning
mode,
Auto/Preset
Switch
will
be
released
and
preset
tuning
mode
will
be
selected,
and
at
the
same
time
Station
A
will
be
selected.
Through
Station
Memory
Switch
A,
Preset
Voltage
set
by
Station
Preset
Contro!
A
and
Preset=L
Signal
are
output.
Through
Auto/Preset
Switch,
both
Preset
Voltage and
Varicon
Voltage
are
applied
to
the
Tuning
Motor
Drive
Circuit,
and
these
voltages
will
be
compared
by
1307
(2/2).
1C307(2/2)
will
detect
the
difference
of
levels
between
the
above
inputs,
Varicon
Voltage
and
Preset
Voltage,
and
if
any
difference
is
found,
Tuning
Motor
will
be
driven,
and
stops
when
the
difference
becomes
nil.
Above
state
will
remain
until
the
other
Station
Memory
Switches
(B,
C,
and
D)
or
Automatic
Scanning
Switches
are
pressed.
Preset=L
Signal
indicates
while
in
preset
tuning
mode.
This
signal
will
be
fed
to
Threshold
Control
Circuit
and
will
turn
ON
D318,
accordingly
threshold
level
will
be
fixed
to
20
dBf.
While
in
auto-tuning
mode,
Oe
Se
VROO1 2K
Preset Switch
Preset Voltage
as
Preset
Signal
is
H,
D318
will
be
turned
OFF,
therefore,
either
20
dBf
or
40
dBf
threshold
level
can
be
selected
with
Threshold
Switch.
Preset
Signal
is
converted
to
Preset
Trigger
Signal
through
C343,
and
while
Preset
Trigger
Signal
is
H,
FM
Mute
will
be
activated.
As
referred
to
in
Fig.
2.3.15,
Preset
Trigger
Signal
is
usually
at
ground
level,
but
at
the
moment
when
Station
Memory
Switch
is
pressed,
minus
differential
pulse
is
generated
first,
then
the
level
is
kept
H
but
it
will
return
to
the
ground
level
again
when
Tuning
Motor
stops.
This
Preset
Trigger
Signal
is
given
to
0311
through
R362,
and
while
Preset
Trigger
Signal
is
H,
Tuning
Indicators
will
go
out.
After
Preset
Tuning
is
made,
if
Station
Preset
Control
A
is
manually
turned,
the
balance
between
the
1C307(2/2)
inputs
will
become
unequal
as
the
1C307-5(2/2)
input
level
is
changed.
The
Motor
will,
therefore,
drive
along
the
rotation
of
the
Station
Preset
Control
A
so
that
the
difference
between
the
said
inputs
will
become
nil.
Manual
operation
with
Station
Memory
Control
will
be
thus
performed.
—* Varicon Voltage
Poo so
GND
ABC
D
+412V
Return Return
Signal(—) Signal (+)
—» Preset Voltage
Fig.
2.3.8
Preset
Voltage
Range
Auto/ Preset
Switch
Rute R335 6.8K
is
rf
_|
VROO4
20K
o—+
=
vROO2
20K
‘aa
Tuning Motor
Drive Circuit
Presa© {
Auto i]
R336 6.8K
Voricon Voltage O—--—s-
Preset
R353
4M
Reset Pulse
R354 40K
R360 100K
WW
ee No Cy
VROO3
20K
Noise Sensor O-»>—
Oo Oo
\: ee
| vRoo4 ;
20K iF Signal ©
Threshold Switch O
VROO2 2K
© Return Signal
|_______© @ Return Signal
D318
Preset
R363 40K
€339_0.033y(W)
Q310
Mono
R355 3.3K
R364 400K
Q341 Base
VR344 20K
R362 400K
R377 4M
ANN
«2
Mute
Out
0306
Preset
Trigger
O
FM
Mute
4
€343 4.5 46V (BP)
R343 330K
Fig.
2.3.9
Preset
Tuning
Circuit
12

(4) Station Detecting Circuit
Refer to Fig. 2.3.10, circuit diagram.
Tuning Signal will become H while a station is detected
by tuning. 1C307-1, the output of 1!C307(1/2), will
become H when IF Signal voltage exceeded the pre-
determined threshold level. IF Signal is the output of FM
demodulator and it corresponds to the strength of radio
field from FM broadcasting stations.
This threshold level is set to either 20 dBf or 40 dBf by
means of the Threshold Switch ON/OFF operation while
auto-tuning, and while preset tuning it is fixed to 20 dBf
as D318 is turned ON.
On the other hand, while a station is already selected, i.e.,
frequency is tuned within a range of center frequency
(fo) +70 kHz, Mute Out Signal from the FM demodulator
is L, and also Noise Sensor Signal is L as the Noise Sensor
Circuit composed of R316, C323, D326, D327 and C324
R356 2.2M
R357
IF Signal ©
R363 10K
20K
0348
» vR344
Preset O
Threshold Switch ©
R359 42K
Noise Sensor
R377 4M
Mute Out ©
C323
{OOP
Composit Signal O--—\W\—-
R316
45K
will not detect inter-station noise.
The said signals are given to Q316. When station is
detected, Q316 will be turned OFF, since both Mute Out
Signal and Noise Sensor Signal are L. Q316 will be turned
ON if Mute Out Signal or Noise Sensor Signal is H. The
output of Q316 and the output of 1C307(1/2) are given as
a condition to control Q310.
When station is detected, 0316 will be turned OFF and
the output of 1C307(1/2) will become H, as a result 0310
will be turned OFF.
At the moment when station is detected, i.e., when 0310
is turned OFF, a differential Reset Pulse=L pulse is
generated through C339, therefore, Auto-tuning Flip-
Flops LT and RT will be reset. Station will be detected
under
the
condition
that
Mute
Out=L
and
Noise
Sensor
Signal=L and IF Signal exceeded the threshold level.
R353 41M
Reset Pulse
© Compulsion Mono
R355 3.3K
© Tuning
R362 400K
Preset Trigger O
Fig. 2.3.10 Station Detecting Circuit
(5) Auto-Tuning
Refer to Fig. 2.3.11, circuit diagram.
(a) Auto-Tuning
General flow will be as follows:
— Automatic Scanning Switch Left/Right is pressed
momentarily
~Auto LT/RT_ Flip-Flop
1C306-8,9,10,11,12,13) is set
— Tuning Motor starts driving until a station is detected
— Station detected (Tuning Signal becomes H and Reset
Pulse is generated)
— Auto LT/RT Flip-Flop is reset
— Tuning Motor kept driving (until tuning is completed,
i.e., AFC Voltage becomes equal to REF Voltage)
— Auto-tuning completed (Tuning Motor stops)
If the Automatic Scanning Switch LT/RT is kept being
pressed, auto-tuning will continue even a station is
detected, i.e., Tuning Motor will not stop as Auto LT/RT
(1C306-1,2,3,4,5,6/
13
Flip-Flop is not reset.
Details along with the general flow would be as follows:
1) Automatic Scanning Switch is pressed momentarily
When Automatic Scanning Switch Left/Right is pressed,
Auto/Preset Switch is activated and auto-tuning mode is
selected, at the same time Auto LT/RT Flip-Flop is set.
Auto
RT
Flip-Flop
will
be
reset
when
Automatic
Scan-
ning
Switch
Left
is
pressed,
and
Auto
LT
Flip-Flop
will
be
reset when Automatic Scanning Switch Right is pressed.
When Auto LT Flip-Flop or Auto RT Flip-Flop is set,
D309 or D310 will be turned ON respectively, as a result
AFC Voltage or REF Voltage is grounded through R390
or R391 respectively, therefore, the balance between the
both inputs (AFC and REF) of the Tuning Motor Drive
Circuit will be lost.
When AFC Voltage is grounded through R390, the output
of 1C307(2/2) in the Tuning Motor Drive Circuit becomes
plus voltage, as a result Q309 is turned ON, Q303 is

turned
ON
and
Q305
is
turned
ON.
Accordingly,
electric
current
passes
Tuning
Motor
via
Q309
and
Q305,
as
a
result
Tuning
Motor
starts
driving
so
that
the
Tuning
Pointer
will
move
to
the
left-hand
side
on
the
Dial
Scale.
On
the
other
hand,
when
REF
Voltage
is
grounded
through
R391,
the
output
of
1C307(2/2)
becomes
0
V,
as
a
result
0308
is
turned
ON,
0303
is
turned
OFF
and
0304
is
turned
ON.
Accordingly,
current
passes
Tuning
Motor
via
0304
and
0308,
as
a
result
Tuning
Motor
will
rotate
to
move
the
Tuning
Pointer
to
the
right-hand
side.
2) Station detected
While
the
Tuning
Motor
is
driving
as
referred
to
in
above
1),
when
a
station
is
detected
as
per
(4)
“Station
Detecting
Circuit”,
the
base
voltage
of
Q310
turns
from
L
to
H,
as
a
result
Q310
is
turned
OFF.
When
Q310
is
turned
OFF,
a
differential
L
pulse
is
generated
at
Reset
Pulse
Signal
through
C339,
as
a
result
Auto
LT
and
RT
Flip-Flops
are
reset
through
D316
and
D315.
Therefore,
D309
and
D310
are
turned
OFF,
accordingly,
only
AFC
and
REF
voltages
are
connected
to
the
inputs
of
1C307(2/2)
in
the
Tuning
Motor
Drive
Circuit.
In
case
the
difference
of
input
levels
to
1C307(2/2)
becomes
nil,
i.e.,
AFC
Voltage
becomes
equal
to
REF
Voltage,
Tuning
Motor
will
stop
its
rotation,
thus
auto-
tuning
is
now
completed.
3)
Automatic
Scanning
Switch
pressed
continuously
When
Automatic
Scanning
Switch
Left
or
Right
is
kept
being
pressed,
its
activation
would
be
as
follows:
When
a
station
is
detected
while
auto-tuning,
the
base
voltage
of
Q310
becomes
L
from
H.
At
this
time
Reset
Pulse=L
is
pulse-likely
output
to
the
reset
input
of
Auto
LT/RT
Flip-Flop.
As
a
result,
Auto
LT/RT
Flip-Flop
is
reset
momentarily,
but
it is
set
again
since
Automatic
Scanning
Switch
is
kept
being
pressed,
thus
auto-tuning
is
continued.
(b) Auto-Return
Auto-return
to
left
end
(Minus
Return
Signal)
or
right
end
(Plus
Return
Signal)
will
be
conducted
respectively
by
VRO002
or
VROO1
in
the
Preset
Switch
P.C.B.
Ass’y.
In
an
ordinary
case,
the
stations
to
be
selected
exist
between
these
ends.
If
Automatic
Scanning
Switch
is
further
pressed
to
the
direction
where
there
should
be
no
station,
Tuning
Pointer
will
reach
either
left
or
right
end
of
the
Dial
Scale.
When
it
reached
either
right
or
left
end,
Tuning
Motor
will
change
its
direction,
therefore
the
direction
of
auto-tuning
will
be
automatically
reversed
and
auto-tuning
will
be
continued
until
a
station
is
detected.
When
detected,
Tuning
Motor
stops
there.
1C305-2
and
1C305-5
are
provided
with
Minus
Return
Signal
and
Plus
Return
Signal,
each
determining
left
end
or
right
end
respectively.
When
the
Varicon
Voltage
exceeds
Minus
Return
Signal
or
Plus
Return
Signal
level,
1C305-1
or
1C305-7
will
become
L
respectively.
Accordingly,
if
Auto
LT
Flip-Flop
is
set,
1C305-1
will
become
L
when
Varicon
Voltage
exceeds
Minus
Return
Signal,
as
a
result,
Auto
LT
Flip-Flop
is
reset
and
Auto
RT
Flip-Flop
is
set
simultaneously
via
D313,
thus
the
auto-tuning
direction
will
be
reversed.
On
the
other
hand,
if
Auto
RT
Flip-Flop
is
set,
1C305-7
becomes
L
when
Varicon
Voltage
exceeds
Plus
Return
Signal,
as
aresult
Auto
RT
Flip-Flop
is
reset
and
Auto
LT
Flip-Flop
is
set
simultaneously
via
D314,
thus
the
auto-tuning
direction
will
be
reversed,
dO
Bus
R390
68K
R380
330K
uning
AN\
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AFC
> O+-—
R391 68K R381 330K
aa REF
a5
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Reset
Pulse
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Auto/Preset
Switch
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Varicon Voltage O
iS) Return Signal O
Tuning Motor
Drive Circuit
Preset Voltage O-—
a.
Preset |
Auto t
=o —o
—o
Preset
Fig.
2.3.11
Auto-Tuning
Circuit
14

(6) Tuning Indicator
Refer to Figs. 2.3.12 — 2.3.16.
While auto-tuning process, both Tuning Lamps will be lit
if tuning has met the radio station. While preset tuning by
means of the Station Preset Control, however, either
Right or Left Lamp will be lit if a station is detected. This
way you can further proceed with tuning to locate a
tuning point of approx. +70 kHz of the center frequency
(fo), when both Lamps will be lit up. Further, in either
case of auto-tuning or preset tuning, both Lamps will not
iNuminate if a station is not detected.
Tuning Pointer Lamp is lit up separately by power ON of
the N-530. Mute Out Signal is output from Demodulator
IC uPC1167C in the IF section, and its characteristic in a
range of +70 kHz of the center frequency (fo) is shown in
Fig. 2.3.13.
In each auto-tuning or preset tuning mode, Mute Out
Signal will become L when tuning frequency is tuned ina
range of +70 kHz of the center frequency (fo) of the
station.
This Mute Out Signal is given to the base of 0314, and
0314 is turned ON, as a result plus voltage is applied to
the base of Q312 and 0313, accordingly 0312 and Q313
are turned ON and both Tuning Lamps will be lit (in this
case 0311 is turned OFF).
Conditions for lightening up both Tuning Lamps are made
by AFC Voltage, Tuning Signal, and Mute Out Signal.
Tuning Lamps will be lit by 0312 and 0313.
AFC Voltage is directly proportional to the S-Curve, and
this voltage becomes 5 V DC when tuning is made at the
center frequency of a station. When tuning frequency
becomes low with respect to the center frequency, AFC
Voltage will become low, and when becomes high, AFC
Voltage will become high. From this AFC Voltage,
direction sensing of tuning becomes possible.
R382 56K
AFC
R376 400K
Mute Out
R362 100K
Preset Trigger ©
R361 100K
Compulsion Mono ©
R374 390
Q315 will be turned ON when AFC Voltage becomes
lower than 5 V DC, i.e., when frequency becomes low
with respect to the center frequency (fo).
(a)
Mlumination
of
Lamp
at
Tuning
by
Station
Preset
Control
Refer
to
Fig.
2.3.14,
timing
chart.
1) No Station is detected
When no station is detected, output of IC307(1/2)
becomes
L
as
the
voltage
of
IF
Signal
is
smaller
than
the
Threshold
Level.
Accordingly,
0310
and
Q311
are
turned
ON,
as
a
result
D320
and
D321
will
be
turned
ON
and
0312
and
Q313
will
be
turned
OFF,
thus
the
Tuning
Lamps will not be lit.
2) Station is detected but out of Tuning
Where a station is detected but tuned to the location
other than the range of +70 kHz of the center frequency
of
a
station,
Mute
Out
Signal
from
1C302
will
become
H,
as a result Q314 will be turned OFF. Therefore, 0311 will
be turned OFF as Q310 is turned ON, i.e., compulsion
Mono=H.
Thus,
one
of
the
Tuning
Lamps
will
be
lit
depending
upon
ON/OFF
of
the
Direct
Sensor
0315.
—7OkKHz fo + 7OkKHz
Mute ON
Mute Out
Mute OFF
Fig. 2.3.13 Mute Out Signal
R365 6.8K
Fig. 2.3.12 Tuning Indicator Control Circuit

Meanwhile,
when
turned
to
the
frequency
100
KHz
lower
than
the
center
frequency,
0315
will
be
turned
ON,
as
a
result
0313
will
be
turned
ON,
thus
Tuning
Lamp
Right
will
light
up.
At
this
time
0312
will
be
turned
OFF,
therefore
the
Tuning
Lamp
Left
goes
out.
On
the
other
hand,
when
tuned
to
the
frequency
100
kHz
higher
than
the
center
frequency,
0315
and
0314
will
be
turned
OFF,
as
a
result
0313
will
be
turned
OFF.
Accordingly
0312
will
be
turned
ON
as
+12
V
is
applied
to
the
base
of
Q312
via
Tuning
Lamp
Right,
D323
and
R365,
thus
Tuning
Indicator
Left
will
be
lit
up.
For
the
Japan
Band,
Tuning
Lamps
Left
and
Right
will
be
connected
oppositely
each
other.
This
is
resulted
from
that
the
Local
Oscillator
of
the
FM
broadcasting
system
for
Japan
Band
is
located
lower
side
(upper
side
for
Overseas
Band)
and
the
polarity
of
AFC
is
reversed.
3)
Station
is
detected
and
tuned
within
+70
kHz
of
the
center
frequency
Where
a
station
is
detected
and
tuned
to
the
location
within
a
range
of
approx.
+70
kHz
of
the
center
frequency
of
a
station,
Mute
Out
Signal
changes
its
level
from
approx.
4
V
to
approx.
0.6
V.
Therefore,
0314
will
be
turned
ON,
and
0312
and
0313
will
be
turned
ON,
thus
both
Tuning
Lamps
will
be
lit.
4)
Detuned
by
further
turning
of
Station
Preset
Control
When
Station
Preset
Control
is
further
turned,
tuning
becomes
out
of
the
range
in
the
reverse
order
of
the
above
procedures.
When
Mute
Out
Signal
becomes
approx.
4
V,
i.e.,
tuning
frequency
becomes
out
of
+70
kHz
of
the
center
frequency,
one
Tuning
Lamp
will
go
out
but
the
other
still
lights
ON.
When
detection
of
the
station
becomes
impossible
by
further
turning
of
the
Station
Preset
Control,
i.e,
when
0311
is
turned
ON,
the
other
Tuning
Lamp
also
goes
out.
ON
AFC
(Q345)
OFF
Mute Out
(Q344)
Q344
Collector
<] Lamp aN
{Q312) OFF
> Lamp be
(Q343) OFF
Fig.
2.3.14
Manual
Preset
Tuning
Timing
Chart
16
(b)
Preset
Tuning
by
Station
Memory
Switch
A,
B,
C,
or
D
Refer
to
Fig.
2.3.15,
timing
chart.
By
pressing
Switch
A,
B,
C,
or
D,
preset
tuning
point
can
be
selected
automatically.
If
a
broadcasting
station
is
preset,
both
Tuning
Lamps
will
be
lit.
(c) Auto-Tuning
Refer to Fig. 2.3.16, timing chart.
Both
Tuning
Lamps
will
illuminate
when
detection
of
a
station
is
made
by
1C307(1/2)
and
when
Mute
Out
Signal
becomes
L
(tuned
within
+70
kHz
of
the
center
frequency
of
a
station)
and
when
Tuning
Motor
stops.
Tuned
Station ON
Memory
Switch OFF
Preset
ov
+
Trigger
. ON [4
Tuning
Motor OFF
ON
Q306
OFF
ON
Q307
OFF
Mute ON
Mute Out
Mute OFF
ON
ap
Lamps OFF
H
Compulsion
n
Mono L
ON
AFC
OFF
:
Fig.
2.3.15
Auto-Preset
Tuning
Timing
Chart
Tuned
Automatic ON
Scanning
|
Switch
Auto LT/RT
Flip-Flop
Tuning
Motor
Q306
Q307
H
Station
Detect L
H
Reset
Pulse
L
Mute ON
Mute Out
Mute OFF
Compulsion
Mono
<b> ON
Lomps
OFF
ON
|
AFC
H
OFF
7
Fig.
2.3.16
Auto-Tuning
Timing
Chart

(7)
FM
Mute
and
Compulsion
Mono
Refer
to
Fig.
2.3.17,
circuit
diagram.
FM
Output
will
be
muted
when
0317
is
turned
ON.
0317
will
be
turned
ON
when
Function
Switch
selects
function
other
than
FM
or
when
Mute
Generator
(0318)
is
activated,
Inputs
to
the
Mute
Generator
consists
of
Mute
Out
Signal.
through
FM
Mute
Switch,
Frequency
Sensor
output
and
Preset
Trigger
Signal.
Either
in
auto-
tuning
or
preset
tuning
mode,
the
output
of
the
Fre-
quency
Sensor
will
become
H
while
Tuning
Motor
is
driven.
As
a
result,
Q318
is
turned
ON
and
C340
is
discharged,
and
Q319
will
be
turned
ON,
thus
FM
Mute
Lamp
will
be
lit.
At
this
time
0317
is
also
turned
ON,
as
a
result
0103
and
Q203
are
turned
ON
and
FM
Outputs
will
be
muted.
A
differential
Preset
Trigger=L
pulse
through
C343
is
generated
at
the
moment
when
Station
Memory
Switch
is
pressed,
then
C343
starts
discharging
and
Preset
Trigger
Signal
becomes
H,
but
becomes
L
when
Tuning
Motor
driving
is
completed.
While
Preset
Trigger
Signal
is
H,
FM
Output
is
muted.
While
in
auto-tuning
mode,
Preset
Trigger
Signal
becomes
H
when
Automatic
Scanning
Switch
is
pressed,
and
becomes
L
when
Tuning
Motor
stops.
Through
FM
Mute
Switch,
FM
Output
will
be
muted
by
the
Mute
Out
Signal
Q349
from 1C302.
If
preset
point
is
out
of
tuning,
inter-station
noise
will
be
output
when
auto-preset
tuning
is
made.
In
this
case
you
can
mute
this
inter-station
noise
by
pressing
FM
Mute
Switch.
Mute
Out
Signal
will
be
given
to
Q318
through
EM
Mute
Switch,
as
a
result
FM
output
will
become
muted,
When
tuning
is
made,
0318
will
be
turned
OFF
but
0319
and
Q317
will
not
be
turned
OFF
unless
discharge
of
C340
is
completed,
thus
FM
Mute
will
be
kept
activated
while
this
period
of
time.
After
completion
of
C340
discharge,
0319
and
0317
will
be
turned
OFF
and
FM
Mute
will
be
released.
Compulsion
Mono
Signal
will
be
generated
and
fed
to
1C303
either
when
station
detection
is
not
made,
or
when
Mute
Out
Signal
is
H,
or
when
Mono
Switch
is
pressed.
As
a
result
Mono
mode
is
selected,
and
Stereo
Signal
of
1C303
will
become
H,
thus
the
Stereo
Lamp
will
go
out.
As
to
Stereo
Lamp,
when
function
is
set
to
FM,
D328
will
become
open,
as
a
result
Stereo
Lamp
ON/OFF
will
be
controlled
by
the
Stereo
Signal
produced
by
1C303.
On
the
other
hand,
when
function
is
set
to
other
than
FM,
D328
will
be
connected
to
Mono
Switch
through
FM
Switch,
as
a
result
Stereo
Lamp
will
be
turned
ON
or
OFF
by
Mono
Switch
operation.
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FM Out
(y
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Fig.
2.3.17
FM
Mute
and
Compulsion
Mono
Circuit
17

2.4. Amplifier Section
2.4.1. Phono Eq. Amplifier
The
Phono
gq.
amplifier
in
the
N-530
employs
a
low-noise
transistor
combined
with
a
low-noise
operation-
al
amplifier
IC
in
the
first
stage
in
order
to
obtain
a
high
S/N
ratio.
:
a
3
Fig.
2.4.1.
shows
the
circuit
configuration,
and
Fig.
2.4.2.
the
noise
equivalent
circuit.
The
thermal
noise
produced
by
the
transistor
base
input
resistor,
hie,
is
given
by
the
following
equation:
En =\/4KThieB
where,
K:
Boltzmann’s
constant
(1.38
x
107°)
T:
Absolute
temperature
B:
Frequency
Band
When
a
signal
source
is
connected
here,
its
impedance,
Rs,
is
connected
in
series
with
the
hie.
The
thermal
noise
produced
by
the
total
input
resistance,
R,
is
given
by
the
following
equation:
Vn =V4KTRB
where, R: hie + Rs
As
shown
in
Fig.
2.4.2.
(a
model
of
a
transistor
showing
the
noise
components),
the
signal
source
impedance
Rs
is
connected
in
series
with
the
transistor
base
input
resist-
ance,
hie.
Because
the
signal
source
impedance,
Rs,
is
normally
larger
than
hie,
the
thermal
noise
produced
by
hie,
En,
has,
in
many
cases,
been
ignored.
However,
if
Rs
is
very
low,
as
in
an
MC
cartridge
(of
the
order
of
several
tens
or
hundreds
of
ohms),
then
hie
will
greatly
affect
the
S/N
ratio.
Nakamichi’s
Models
N-410,
610,
630
and
730
has
been
used
to
reduce
En
with
the
triple-transistor
system
—
a
circuit
with
three
transistors
connected
in
parallel
—
to
decrease
hie
by
a
factor
of
3,
thus
En
is
reduced
to
1/3
of
the
conventional
level.
However,
N-530
employs
single
transistor,
specially
designed
to
reduce
En.
Furthermore,
the
N-530
uses
a
low-noise
operational
amplifier
IC,
which,
together
with
above
system,
reduced
the
noise
level
to
—138
dB
or
less.
The
characteristics
of
semiconductors
generally
differ
to
some
extent.
To
avoide
differences
of
offset
voltage
due
to
differences
in
semiconductor
elements,
a
semifixed
variable
resistor
is
inserted
between
the
positive
power
source
and
the
positive
voltage
terminal
of
Phono
Eq.
Amplifier
to
regulate
the
offset
voltage
and
obtain
a
low
distortion
factor.
18
Z Q4
2SC2240(BL
input O
Ytr-
Q40:
Rs:
hie:
En:
vn:
AW
+—
AW
=
Slee
+48V
RC45590D :
Be
——O Output
ww
ae
WW
——O
-18Vv
Rs
Signal
Transistor current noise
Signal source impedance
Transistor
base
input
resistance
Thermal noise by hie
Thermal! noise by Rs and hie
Fig. 2.4.2

2.4.2. Subsonic Filter
The frequency response of ordinary hi-fi phono cartridges
covers the subsonic range. The resonance point is near
10 Hz with a peak of 5 to 15dB. These factors are
determined by the mass, compliances and damping resist-
ance of the cartridge and tone arm. Further, near the
resonance frequency, the disc record is likely to be
eccentric or warped, or the turntable vibrates abnormally.
In extreme cases, the resonance frequency increases to the
level of disc record playback signals (the worst condition
occurs when the vibration caused by the speaker is fed
back to the cartridge via air or floor vibration). Usually,
the subsonic effect thus produced is not found. Because
of inter-modulation distortion, the subsonic effect causes
unclean sound from amplifier, speakers or tape decks. It
especially affects such systems whose response curves
cover lower frequencies (note that, if the woofer moves
unsteadily during playback of disc records, the above-
mentioned adverse effect can be produced).
The turntable, cartridge and tone arm must be improved to
completely eliminate subsonics, However, even improved
turntable, etc. could not completely eliminate subsonics.
One solution of this problem so far achieved is using
commercially available preamplifiers that incorporate sub-
sonic filters. But most of them shows poor attenuation
curves of 6dB/Oct. or 12 dB/Oct., and they can not
sufficiently eliminate subsonics. And they have fault to
attenuate the low frequency band (near 30 to 40 Hz). The
subsonic filter used in the N-530, based on the new active
O +Vec
Input ©
R136 68K
be
40u46V
Output
R439 100K
O -Vec
Fig. 2.4.3 Subsonic Filter Circuit
19
filteration
technology,
can
realize
an
ideal
filter
character-
istic.
Fig.
2.4.3.
shows
the
subsonic
filter
of
the
N-530.
The
portion
represented
by
Fr
is
generally
known
as
a
twin
T
filter,
[ts
characteristics
are
illustrated
in
Fig.
2.4.4.
(1).
As
shown,
the
curve
of
the
twin
T
filter
rapidly
drops
at
20
to
50
Hz,
and
attenuation
at
below
5
Hz
is
rather
small.
These
demerits
have
been
smartly
eliminated
by
the
N-530
as
follows:
Improvement
1:
Improved
Twin
T
Filter
with
Boot
Strap
As
shown
in
Fig.
2.4.3.,
the
output
from
the
twin
T
filter
is
amplified
by
Q105
and
taken
out
from
its
emitter.
This
output
provides
positive
feedback
to
the
base
of
Q105
through
C120
and
R133.
This
greatly
reduces
the
level
down
in
the
range
20
to
50
Hz.
For
greater
attenuation
in
the
range
below
5
Hz,
R135
is
added
to
lower
the
load
impedance
of
the
filter
and
to
change
the
impedance
of
each
element
so
that
the
asymmetric
curve
as
shown
by
Fig.
2.4.4.
(2)
can
be
achieved.
Improvement 2: Addition of CR Filter
The
curve
shown
in
Fig.
2.4.4.
(2)
is
satisfactory
for
the
subsonic
filter
except
insufficient
attenuation
at
below
5
Hz.
Besides
the
N-530
uses
a
CR
filter
consisting
of
C122
and
R139
to
achieve
a
more
ideal
subsonic
filter
curve
as
shown
by
Fig,
2.4.4.
(4).
(In
Fig.
2.4.4.
(3)
shows
the
CR
filter
curve
and
(4)
is
a
combination
of
curves
(2)
and
(3).)
-10
8
ATTENUATION (48)
!
$
a
2
3
5
10
20
30
50
400
FREQUENCY (Hz)
Fig. 2.4.4