Text preview for : hfe_pioneer_sx-3900_service.pdf part of Pioneer hfe pioneer sx-3900 service Pioneer Audio SX-3900 hfe_pioneer_sx-3900_service.pdf
Back to : hfe_pioneer_sx-3900_servi | Home
www.hifiengine.com
$eftice nual
FM Iuartz Locked
S T E R E OR E C E I V E R
six-3s|oo
()proNEER'
www.hifiengine.com
M O D E L S X . 3 g O O O M E SI N T W O V E R S I O N S I S T I N G U I S H E D S F O L L O W S :
C D A
Voltage Remarks
Type
KU 120Vonly U . S . A .m o d e l
5/U I 10V, 120V, 22Oand240V (Switchable) U . S .M i l i t a r y m o d e l
This servicemanual is applicableto the KU type. When repairingthe S/G type, please the
see
additional servicemanual (seepages -56l..
47
CONTENTS 1. SPECIFICATIONS
1. spECtFtcATtoNS 2 P o w e rA m p l i f i e rS e c t i o n
2 ' F R o NP A N E L C I L T T I E S
r FA a
C o n t i n u o uo w e0 u t p u0 f 1 2 0 a t t s x p c h a n -
Ps r t w er
3' BLocK IAGRAM
D 7 n e l ,m i n . a t 8 o h m sf r o m 2 0 H e r t tzo 2 0 , 0 0 0
,
4 . c l R C UD E S C R I P T I o N S
lr H e r t zw i t h n 0 m . r e t h a n0 . 0 0 5 % o l a lh a r m o -
t
4 . 1 F MT u n eS e c t i o n
r 8 n i Cd i S t O f t i O n .
4.2 AM Tuner Section 9 (20
Distortion Hertz 20,000
To,rlHarmonic to Hertz,
4.3 Audio Section 9 g ohms)
4.4 DisplayCircuits ....... 11 c o n t i n u o u s r a t e d p o w e r o u t p u tN.o m o r e t h a n 0 . 0 0 5 %
.
4.5 P r o t e c t i o nC i r c u i t 13 6 0 w a t t s p e r c h a n n e lp o w e r
current
4'6 Surge suppressor " " " ' l5 oirioriion rrrrrltrl;f ;::ltjT:"fl
,",1r',jlltr,r.ion iuo
5' DISASSEMBLY '
' 15
1 E
c o n t i n u o ur a t e dp o w e ro u t p u t . . N o m o r et h a n0 . 0 0 5 %
s
6 . P A R T SL O C A T I O N 16 6 0 w a t t sp e rc h a n n ep o w e r
l
7 . D I A L C O R DS T R I N G I N G. 18 output ' . . . ' N o m o r e h a n0 . 0 0 5 %
t
g. ADJUSTMENTS Frequency Response
*! aa
8.1 Audio
Section 1e T iorTln?,t'.2
rnpr.s.nriiiui,vli,.np.oun..t,i;ff
'l
8.2 T u n e rS e c t i o n . 20 ..... V/50kilohms
9, SCHEMATIC IAGRAM D 24 OUtPUt
' ' ' ' ' A' B' A+B
10. p . c . B o A R D Sc o N N E C T T o N T A G R A M
D 29 -speaker
D a m p i n g a c t o r( 2 0 H e r t zt o 2 0 , 0 0 0 e r t z , o h m s )
F H 8
I1.PARTSLIST. 35 ...60
12. EXpLoDED tEW
v 41 Hr..;; r t r . i r .i i H i , r r r o r t c i r c u i t eA ,n e t w o r k )
o
46 ""' 115d8
1 3 .P A C K | N G . . . .
A D D T T T O N A LE R V T CM A N U A L F O RS / GT Y P E
S E 41 Preamplifier ection S
In p u t ( S e n s i t i v i t y / l m p e d a n c e )
PHONO ,2. . . 1 2.5mV/50 ilohms
k
A U X , T A P EP L A Y 1 , 2 ,
A D A P T O R I N. . . ... 150mV/50kilohms
P h o n o v e r l o a d e v e l( T . H . D . . 0 0 5 %1 , 0 0 0H e r t z )
O L 0 ,
PHONO.2... 1 300mV
O u t P u t( L e v e l /m P e d a n c e )
l
T A P ER E C1 , 2 . A D A P T O R U T O
150mV
P R E A M P U T ( R L :5 0 k i l o h m s )
O
. . . . 1 V l 1k i l o h m sV o l u m e : a x . )
( m
T o t a l H a r m o n i c i s t o r t i o n 2 0 H e r t zt o 2 0 . 0 0 0 e r t z )
D ( H
P H O N O . 2 ( R E CO U T ) . . . . . . N o m o r et h a n0 . 0 0 5 %
1
( 1 0 Vo u t p u t )
www.hifiengine.com
sx-3900
A U X , T A P EP L A Y 1 , 2 . A D A P T O R N
I AM TunerSection
No more than 0.005% S e n s i t i v i t ( l H F , F e r r i t ea n t e n n a . . 300sV/m
y )
(10V output) (lHF, Ext. antenna)" . 1SpV
F r e q u e n cR e s p o n s e
y Selectivity 30dB
P H O N O RI A A E q u a l i z a t i o n )
(
S i g n a l - t o - N o i sR a t i o
e 50dB
. . . 2 0 H e r t zt o 2 0 , 0 0 0 e r t zt 0 . 2 d B
H lmageResponse atio R 40dB
A U X , T A P EP L A Y 1 , 2 ,A D A P T O R U T O l F R e s p o n sR a t i o . .
e 40dB
+9
' ' ' ' ' 7 H e r t zt o 8 0 0 0 0 H e r t z d B Antenna F e r r i t eo o p s t i c k
l
Ton. contror an t e n n a
B A S S. ! 4 d B / ! 7 d B( 1 0 0 H 2 )
Audio Section
f u rnoverFrequency2OOHz/
: 400H2
O u t p u t( L e v e l /m p e d a n c e )
l
TREBLE + g d B / t 7 d B1 0 k H z )
(
FM(100% od.). M 650mV/2.4 ilohms
k
Tu rnoverFrequencv2kHzI 4k{z
:
Filter A M ( 3 0 %M o d . ) . 20OmV
/2.4 kilohms
L O W .. 1 5 H z( - 6 d B / o c t . ) Semiconductors
HIGH. 8 k H z( - 6 d B / o c t . ) lCs... t5
L o u d n e sC o n t o u r( V o l u m e o n t r o ls e t a t - 4 0 d B p o s i t i o n )
s c FETs. o
. . . . + 6 d B( 1 0 0 H 2 ) , 3 d B( 1 00 0 0 H 2 )
+
T r an s i s t o r s 89
H u m a n dN o i s e l HF , s h o r t - c i r c u i t e dn e t w o r k )
( A ,
Diodes 62
PHONO . .. . .. 86dB
A U X , T A P E L A Y1 , 2 ,
P M iscellaneous
ADAPTORIN... 10 5 d B Power equirements
R AC 120V.60H2
Attenuator. -20d8 Power onsumption
C 3 5 0 W( U L )
FM Tuner Section Dimensions 5 2 6 ( Wx 1 7 6 ( H )
) x
4 5 2 ( D )m m
U s a b l S e n s i t i v i t yHF)
e (l 9 . 8 d B f( 1 . 7 p V )
2 0 - 1 1 / 1 6 ( w l 6 - 15 / 1 6
x
5 0 d BO u i e t i n g e n s i t i v i t y
S
( H ) x 1 7 - 1 4 / 1 6 ( Dn il
MONO 14.2dBf(2.8pV)
Weight(without package) 2Okg(441b 2ozl
STEREO 3 6 d B f( 3 4 . 7 p V )
S i g n a l - t o - N o iR e t i o
sa Furnished
Parts
MONO 8 3 d B( a t 6 5 d B f ) O p e r a t i n gi n s t r u c t i o n s 1
S T ERE O 7 8 d B( a t 8 0 d B f ) FM T-type antenna 1
Distortionat65dBf ( )
MONO 100H2. 0.1o/o * Measured pursuant to
the Federal Trade Commission's Trade
lkHz . o.o7% Regulation rule on Power Output Claims for Amplifiers.
6kHz ' oJ%
NOTE:
S T E R E O1 0 0 H 2 . O.27o
Specifications and the design subject to possible modifications
ikHz . o.15% without notice due to improvements.
6kHz O.2To
C a p t u r eR a t i o . . 1.0d8
A l t e r n a t e C h a n n e lS e l e c t i v i t y
400kHz ......80dB
S t e r e oS e p a r a t i o n
1 k H z . . . . . . . 5 0 d 8
3OHzto15kllz. ...... 35dB
F r e q u e n c yR e s p o n s e
....2OHzto15kHz1!jaa
Spurious
Response . . . . . . . 100dB
Ratio
lmageResponseRatio ... 90dB
lFResponseRatio.. .... 100d8
AMSuppressionRatio ... 60dB
SubcarrierProduct atio . . . . . . .
R 64dB
SCARejectionRatio .... 64dB
M u t i n gT h r e s h o l d 1 9 . 2 d B f( S g V )
Antenna Input . 300 ohms balanced,
75 ohms unbalanced.
www.hifiengine.com
2 . F R O N T P A N E LF A C I L I T I E S
SWITCH
SWITCH O TREBLE URNOVER
T
O POWER Use this switch to change over
the frequency in which
SetthisswitchtooNtosupp|ypowertothereceiver. treble control is starting
is setto ON' because the sound adjustment with the
Therewill be a shortdelaywhen it to take effect' Select 2k{z
or 4kHz in accordance
to suppressthe
the muting circuit has been actuated withthecharacteristicsofyourIisteningroomandof
generated when the
unpleasant noisethat is sometimes preference'
y o u r s p e a k e r sa n d w i t h y o u r g e n e r a l
,
Poweris switched on andoff '
@ noRProRswlrcH
@ BASSTURNOVERSWITCH
frequency in which SetthisswitchtooNwhenreproducingsoundfroman
Use this switch to change over the optional componentwhich is connected
to the ADAP-
bass control is starting p o s i t i o nf y o u a r e
the sound adlustment with the T O R i a c k s A l w a y s e ti t t o t h e u p p e r
. s i
or 400H2 in accordance
to take effect. Select 200H2 n o t u s i n g c o m p o n e nw i t h t h e s e e r m i n a l s '
a t t
withthecharacterlstics'ofyourIisteningroomandof
preference'
y o u r s p e a k e r sa n d w i t h y o u r g e n e r a l
, @ T A P ED U P L I C A T E W I T C H
S
you want to duplicate or
Set this switch to ON when
@ EASS ND TREBLE ONTROLS
A C
edit a pre-recorded tape using
two tape decks'
bass and the treble'
Use these controls to adiust the
ON and turn the bass
lf you set the tone switch to @ T A P EM O N I T O R W I T C H
S
a r e c o r d i n gi n
controItotherightfromitscenterposition,youwi||be E m p l o y f o r t a p e p l a y b a c ko r t o m o n i t o r
ab|etoemphasizethesoundinafrequencyrangewhich progress.
bassturnover switch'
is lower than that selectedby the 1: P l a y b a c ko r m o n i t o r i n g o f a t a p e d e c k c o n -
position
C o n v e r s e l y t, u r n i n g t h i s control from the center nected to the TAPE 1 jacks'
to the left will attenuate the sound' position when not
SOURCE: Be sure to set to this
adjust the sound in a
You can use the treble control to usingthe tape deck for playbackand moni-
by the treble turn-
frequency higher than that selected tori ng'
con-
over switch. 2: P l a y b a c ko r m o n i t o r i n g o f a t a p e d e c k
nected to the TAPE 2 jacks'
@ T O N ES W I T C H
bassand treble
Set this switch to ON when adjustingthe NOTE:
be sure to set this
tone control When listeningto records broadcasts'
or
c o n t r o l s .W h e n s e t t o t h e O F F p o s i t i o n 't h e Soundwitt not be obtainedfrom speakers
switch to SOURCE'
circuitsaredisengagedandfrequencyresponseisf|at. if it is setto 1 or 2.
Thisfunctionisconvenientforcheckingphonocartridge
room acoustics'
a n d s p e a k e rt o n e q u a l i t y a n d l i s t e n i n g
www.hifiengine.com
six-39cl(f
) BALANCECONTROL @ L O WF I L T E R W I T C H1 5 H 2 )
S (
U s e t h i s c o n t r o l t o b a l a n c et h e v o l u m e o f t h e l e f t a n d D e p r e s st h i s s w i t c h i n t h e e v e n t t h a t t u r n t a b l e r u m b l e ,
r i g h t c h a n n e l s .F i r s t , h o w e v e r , s e t t h e m o d e s w i t c h t o recordingcutting noise or other low frequency noise
M O N O . l f t h e s o u n d a p p e a r s o b e l o u d e ro n t h e r i g h t , i t
t b e c o m e s o b j e c t i o n a b l e .A t t e n u a t i o n i n t h e f r e q u e n c y
means that the volume of the right channel is higher. bandbelow 15Hz is6dB/octave.
Turn the balancecontrol to the left and adjust.Con-
v e r s e l y ,i f t h e s o u n d a p p e a r st o b e l o u d e r o n t h e l e f t , i t G ) H I G H F I L T E R W I T C H8 k H z )
S (
meansthat the volume of the left channel is higher. D e p r e s s h i s s w i t c h i f r e c o r d s c r a t c hn o i s e o r o t h e r h i g h
t
T h e r e f o r e . t u r n t h e b a l a n c ec o n t r o l t o t h e r i g h t a n d f r e q u e n c y n o i s e b e c o m e so b j e c t i o n a b l e A t t e n u a t i o n i n
.
a dj u s t . A f t e r a d j u s t i n g , r e t u r n t h e m o d e s w i t c h t o t h e f r e q u e n c yb a n d a b o v eS k H z i s 6 d B / o c t a v e .
STEREO.
) POWER ETER
M
@ M O D ES W T T C H This meter allows you to read out the rated power level
U s e t h i s s w i t c h f o r s e l e c t i n gm o n o o r s t e r e o p e r f o r m - o n t h e f l u o r e s c e n td i s p l a y t u b e w h e n s p e a k e r s i t h a
w
a nces . nominal impedanceof 8 ohms are connected to the
STEREO: Set to this position for normal operations. speakererminals.
t
MONO: W h e n s e t t o t h i s p o s i t i o n ,t h e l e f t a n d r i g h t
c h a n n e l s i g n a l sw i l l b e m i x e d a n d r e p r o -
@ DrALPOTNTER
This pointer indicateshe broadcastingtations.
t s
duced monophonically from both speaker
systems. @ rnnSTEREo
rNDrcAToR
o voLUME ONTROL
C T h i s i n d i c a t o rl i g h t s u p w h e n r e c e i v i n g n F M s t e r e o
a
p r o g r a mf t h e F M m u t i n go f f s w i t c hi s r e l e a s e d .
i
Use this control to adjust the output level to the
s p e a k e r s n d h e a d p h o n e sT u r n i t c l o c k w l s et o i n c r e a s e
a . @ oUARTZLOCKEDND|CATOR
|
t h e o u t p u t l e v e l .N o s o u n d w i l l b e h e a r d i f y o u s e t i t t o This indicatorlightsup after the optimum tuning point
-. The scale is graduated in dB which indicate the
h a s b e e n o b t a i n e da n d d i s p l a y s h a t t h e r e c e i v i n g t a t ei s
t s
a t t e n u a t i o nw h e n t h e m a x i m u m o u t p u t l e v e li s 0 d B .
stabilized y the built-inquartz lock circuit.
b
) M U T I N GS W I T C H D SIGNAL INDICATOR
Set this switch to the *20d8 position to attenuate the
T h i s i n d i c a t o r l i g h t s i n s e q u e n c er o m l e f t t h r o u g h r i g h t
f
a u d i o o u t p u t i n d i c a t e db y t h e v o l u m e c o n t r o l b y 2 0 d B .
d u r i n g t h e t u n i n g o f a n A M o r F M b r o a d c a s ti n a c c o r d -
T h e r e i s n o n e e d t o a d j u s tt h e v o l u m e c o n t r o l i f y o u u s e
a n c e w i t h t h e s t r e n g t h o f t h e s i g n a l sb e i n g r e c e i v e d .
this switch when turning down the audio output tem-
The optimum tuning point is where the maximum
p o r a r i l y a n d w h e n c h a n g i n g v e r r e c o r d so r t a p e s .
o
n u m b e r o f i n d i c a t o r sl i g h t .
G ) H E A D P H O NJ A C K
E rNDrcAToR
@ rururNG
P l u g t h e h e a d p h o n e si n t o t h i s j a c k w h e n y o u w a n t t o W h e n t u n i n g i n a n F M s t a t i o n ,t h e o p t i m u m r e c e p t i o n
l i s t e nt h r o u g h y o u r s t e r e oh e a d p h o n e s . p o i n t i s i n d i c a t e dw h e n t h e c e n t e r i n d i c a t o r l i g h t s u p .
Releaseboth speaker switches if you want to listen to W h e n t h e l e f t i n d i c a t o rh a s c o m e o n , r o t a t e t h e t u n i n g
t h e s o u n dt h r o u g h y o u r h e a d p h o n e s n l y .
o k n o b s l i g h t l y c l o c k w i s e .W h e n t h e r i g h t i n d i c a t o rc o m e s
(E SPEAKER WITCHES
S o n , r o t a t e t h e k n o b s l i g h t l yc o u n t e r - c l o c k w i s e .
D e p r e s st h e s w i t c h c o r r e s p o n d i n g o t h e s p e a k e r s o n -
t c @ F R E O U E N CD I S P L A Y
Y
n e c t e d t o t h e S P E A K E R St e r m i n a l s( A o r B ) o n t h e r e a r T h i s i n d i c a t e s h e f r e q u e n c yw h i c h i s t u n e d .
t
panel.
W i t h F M r e c e p t i o n ,t h e l e t t e r s " F M " a p p e a ro n t h e l e f t
You can depress both of these buttons to listen to the
of the displayand "MHz" on the right. With AM recep-
sound from two pairs of speaker systems at the same t i o n , " A M " a p p e a r so n t h e l e f t a n d " k H z " o n t h e r i g h t .
time. These change when the function selectorposition is
c h an g e d .
@ TUNING NOB
K
U s et h i s k n o b t o t u n e i n t o b r o a d c a s t i n g t a t i o n s .
s
5
www.hifiengine.com
@ FUNCTION ELECTOR
S
@ F M M U T I N GO F F S W I T C H to the
tuned Deoress the function switch which corresponds
When this switch is released nd an FM broadcas a down first
i n s i d et o s u p p r e s s h e
t program source.Turn the volume control
in, the muting circuit is activated while the
between the broadcasting b e f o r e s e l e c t i n ga d i f f e r e n t f u n c t i o n s w i t c h
annoying interstation noise
the broadcast- s o u n d f r o m o n e p r o g r a ms o u r c ei s b e i n g r e p r o d u c e d '
f r e q u e n c i e so r n o i s e - f r e e e c e p t i o n W h e n
f r '
FM: Depress switchfor FM broadcasts'
this
ing station is far away or when receiving stationin a a
AM: Deoress switchfor AM broadcasts
this
f r i n g e a r e a ,s e t t n e s w i t c h t o t h e O F F p o s i t i o na n d t h e n an
with a strong AUX: D e p r e s st h i s s w i t c h w h e n l i s t e n i n g t o
tune in. lf there is a broadcastingstation to the AUX
audio component connected
signal level on the air next to a station whose program
to tune in iacks.
you want to receive, you may not be able p l a y i n ga r e c o r d o n
P H O N O 2 : D e p r e s sh i s s w i t c h w h e n
t
s a t i s f a c t o r i l yb e c a u s ethe sound will be drowned out
set the FM the turntable connectedto the PHONO 2
b y t h e s t r o n g e r s i g n a l s ' I n c a s e sl i k e t h i s ' j a ck s .
MUTING OFF switch to OFF (depressedosition)and p
p l a y i n ga r e c o r d o n
work when the P H O N O 1 : D e p r e s sh i s s w i t c h w h e n
t
tune in. The muting circuit does not the turntable connected to the PHONO
1
tuner is receiving A M b r o a d c a s t s 'l f t u n i n g h a s b e e n
h a sb e e n iacks.
p e r f o r m e da f t e r t h e F M M U T I N G O F F s w i t c h
selected. the quartz locked NOTE:
depressed and a station at a ilme'
the LOCKED OnlY one function switch should be depressed
circuit is set to the OFF mode and
i n d i c a t o rd o e s n o t light.
@ L O U D N E SS W l r c H
the volume
@ FM 25PSSWITCH When listening to a performance with
and the bass
Depressthis switch when listening to
a Dolby* FM control turned down, depressthis switch
broadcast; otherwise keep this switch at the released a n d t r e b l ew i l l b e a c c e n t u a t e d '
f i t h a r d e rt o
position. Whenthe volumeis low, the human ear inds
volume is high'
h e a r t h e b a s sa n d t r e b l e t h a n w h e n t h e
for
The loudnessswitch is thus designedto compensate
@ ) B R I G H T N E SS E L E C T O R
S t h i s d e fi c i e n c y . B y d e p r e s s i n g h i s s w i t c h '
t t h e b a s sa n d
of the power and the sound
Use this switch to select the brightness treble come through much more strongly
meterand the frequencY isPlaY' d control is
takes on a puncn even when the volume
or other
B R I G H T : W h e n u s i n g t h e r e c e i v e ri n d a y l i g h t turneddown.
bright locations'
DIM: A t n i g h t o r i n d a r k l o c a t i o n sw h e n t h e e x i s t -
i n g b r i g h t n e s ss t o o h i g h '
i
*Theword,,Dolby''isatrademarkofDoIbyLaboratoriesInc.
www.hifiengine.com
sx-39clcl
3. BLOCK DIAGRAM
Tuner Section
r c ( H A l 2 0 1)
0
OUARIZ LOCKEO
AM TUNER
5-POINT SIGNAL
I N D I C A T O RO R I V E
A M O
rUN]NG INDICATOR FREOUINCY OISPLAY
FM MHz
,ODDD
, t_, t_t.t_t t_t
AM KHT
CoUNTER Oi - D5
TIME DIVISION
7- SE6MNT OECODR
ROM
s1s2 s3 s4
Audio Section
.":-
IAPE 1 _-. ^ ADAPrcR
REC PLAY OUT IN
ar lr
R CnANNE- . IHL SAME A5 IHF L CHAN\EL )
FREA!ENCY
FL TUSE
'UIER
SECTION
www.hifiengine.com
ap-
IF system IC (PA300?-A), it is amplified and
4 . C I R C U I TD E S C R I P T I O N Sptiei to a crystal detector (seeFig' 4-1) which con-
a series
sists of diodes connected in parallel in
4 . 1 F M T U N E RS E C T I O N resonance circuit equipped with a crystal resona-
i.r. irt" resonance frequency is the sameas the IF
Front End
a 4 fr"qr".r"y (10'?MHz), which meansthe impedance
The FM front end of SX-3900 includes in the out-
MOS FET- at it ls time will be minimal, resulting
ganged tuning capacitor, a dual-gate level' If the input
a modified fut being reduced to a minimum
Eo"Too"A l-slage RF amplifier' and capaci-
This oscillator is a iruq.r"rr"y increases-the reactance of the
ai;; circuit llcal oscillator' of the
a vari-cap tanie stage(C) is reduced,and the reactance
uoiiug" controled oscillator employing in AM
diode)' When the.quartz-lock ir"rar"tun"u stage (L) increased,resulting
(varia'ble capacitance positive portion
is not in Jetection by D2 which leavesthe
,yrt"..t (refer to "Quartz-lock system") decreases'
is applied to the of the IF signal.If the input frequency
operution, a constant voltage reac-
L stage reactanceis decreasedand C stage
diode. resulting in AM detection by D1
tance increased,
lF Amplifier and Detector which leaves the negativeportion of the IF signal'
ceramic it'r" t stageand C stagereactances inctease as the
Theseemploy 3 ICs and 3 dual-element is
filters. fne lC (HA1201) of the first 2 stagecon- degree oidetuning in the respectivedirections
differential amplifier current- in&eased, resulting in a subsequent increase in
stitutes a single-stage S-curve
ii-lti.rg limitet. The IC (PA300?-A)-in
the third the detector output. By thus attaining
possible'
stage, improvement on the
an former iF systemIC characteristics,FM detection becomes
devia-
liigool ai, includes an iF iimiter amplifier' Since the IF signalis an FM signalfrequency
cir- tiorl-a"" to iodulation, it will be symmetrical
quadrature detector, meter drive' and other is
cuits. Performance in terms of distortion' S/N about a central axis. And if the central frequency
and other parameters' equal to the resonancefrequency, the detector out-
ratio, delay characteristics,
,ho*, a marked improvement in comparison
to o,rt OC level will be zero. If, however,there is any
the PA3001-A. displacement in the central frequency, frequency
become
deviation in respect to the detector will
Ouartz-LockSYstem aryrrr-utri"a1, resulting in the generationof a DC
The quartz-lock systemfeaturedin the
SX-3900 This DC voitage is passedthrough LPF1
stereo receiver is a frequency serl/o control system (IF filter) and LPF2 (AC filter) to form a correc-
"liiug".
displacement capaci-
employing a crystal resonator' Any iion voltage which is applied to the variable
i.r itt"-lntlrmediate frequency (IF) is detected as a tancediodeinthelocaloscillator,therebycorrect-
with a constant
DC voltage by the discriminator (equipped ing the oscillator frequency to obtain a
crystal resonator)' resulting in the local oscillator tn' (i.e. a constanttuned frequency)'
detec-
ir"qt"r-r"y being corrected and subsequently Since the central frequency of the crystal
servocon- the crystal resonator' tuned
locked. This extremely stablefrequency tor is regulated by
that tuned frequencies are ob-
trol system thus ensures frequencies of exiremely high stability
remain tuned securelyfor aslong asrequired' tained.
of the
When the IF signalappearsat pin no'17
l c ( P A5 0 0 7 - A )
F M F R O N TE N D
CRYSTAL DETECTOR
| ----, I
: ( L ) 1 3 + i
CI R C U T
I
F i g .4 - 1 O u a r t zL o c kS Y s t e m
a www.hifiengine.com
sx-39clo
o Limiting the Locking Range 4 . 3 A U D I OS E C T I O N
If the quartzJock range is too wide, it will P h o n o q u a l i z e rm p l i f e r
E A i
overlap with strong adjacent broadcasting fre- Fig. 4-3 shows the basic configuration of the
quencies and result in considerable tuning diffi- circuit. An S-N ratio of 86dB (at 2.5mV input,
culties. A DC amplifier is therefore used as a IHF-A) has been achieved by using a ultra-low-
limiter (limiter action by NFB circuit zener diodes) noise PNP transistor (2SA978) at the first stage,
which restricts the voltage applied to the variable and reducing the signal source resistance and
capacitance diode, thereby limiting the quartz-lock equalizer element impedance. High voltage gain is
range. provided in the following stage by a bootstrap cir-
A DC voltage appears at pin no.13 of the IF cuit. The output stage is a complementary sym-
system IC (PA3007-A) when the antenna input metrical SEPP circuit. The high voltage utility
ievel drops below 5pV, or when the tuned fre- factor of the SEPP circuit provides a high maxi-
quency has been detuned by more than t100kHz. mum output voltage. Dynamic range of the
This DC voltage (FM muting signal) is applied to equalizer amplifier is therefore wide and overload
the gate of Q2 (FET) via a Schmitt circuit, result- input level at 0.005% distortion is 300mV (rms at
ing in the FET being turned on, and the quartz- lkHz).
Iock circuit being turned off.
Multiplex Decoder
The recently developed multiplex decoder IC
(PA4006-A) combines MPX decoding with muting
functions in a single IC, thereby handling the tNHMrl
functions of the more conventional MPX IC
(PA1001 A) and AF MUTING IC (PA1002-A).
Distortion ratings and S/N ratio have been
further improved by incorporating a chopper type
MPX decoder. The chopper type switching circuit
F i g .4 - 3 P h o n o E q u a l i z e A m p l i f i e r
r
(see Fig. 4-2) operates by switching the signal
either to ground or to the through circuit, thereby Tone Control
eliminating the generation of unwanted noise or Fig. 4-4 shows the basic configuration of the
distortion. Furthermore, since the PA4006--4 fea- circuit. This circuit is an NFB type tone control
tures DC direct-coupled switching with the detec- with IC (HA12017P).
tor, there is no deterioration in separation at the Tone control (BASS, TREBLE) is accomplished
Iow frequency end. by providing the tone amplifier NFB circuit with
Besides the decoder and muting circuits, the a frequency selective characteristic. The capaci-
PA4006-.4 also incorporates the pilot signal cancel- tance of C7-C4 are changedby the TURNOVER
ler, stereo auto selector, VCO killer circuit, MU'l switches (by adding another capacitors in parallel)
amplifier. and MUT control circuit. to provide selectionof the frequency.
Composite The NFB circuit is changedto a flat frequency
si g n a l characteristicwhen the TONE switch in the OFF
oosition.
Inprt Output
.}.
JUIIUUUIJUIJU' I
--'I
,in"r'r
switchins S/
n L
F i g . 4 - 2 C h o p p e rT y p e S w i t c h i n gC i r c u i t
4.2 AM TUNER ECTION
S
The AM tuner section consists of a 2-ganged
tuning capacitor plus an IC (HA1197) which con-
tains a 1-stage RF amplifier, converter, 2-stage IF
amplifier, detector, and AGC circuit.
The AM STEREO OUT terminal on the rear
panel is for connecting to an AM stereo broadcast
decoder adaptor. The signal appearing at this ter-
minal is the converter output passed via a buffer Tone Control
(emitter-follower) stage.
www.hifiengine.com