Pioneer SX-7 User manual

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Shot/,n tn thb photo b Model SX-7.
ORDER
NO.
ARP-047-O
COMPUTER
CONTROLLED
STEREO
RECEIVER
sx-7
sx-6
SX-s.SiX-EiL
SX-,QISX-4L
. The AM tuner of SX-4L
wave-bandtuner with MW
LW
(long
wave).
and SX-SL is a two
(medium
wave)and
Model SX-7 (and SX-6, SX-5 and SX-4) arenew
types of receivers featuring microcomputers for
easier
operation. The AM/FM tuner stagesincorpo-
rate quartz PLL synthesizers for high stability,
while the power amplifier stageis a non-switching
amplifier which achievesclassA quality with class
B efficiency (not included in the SX-4 model).
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O AUG.1981
Printed
in
lapan

BLOCKDIAGRAMS
SX.4/KU
FM FRONT ENO FM IF AMP A DETECTOR FM MPX STEREO OEMOOULATOR FREQUENCYOISPLAY
-
toon
Fx l--
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ii#n i*---- l TUNING OETECTOR
IC P06004
R6
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CIRCUITDESCRIPTIONS
Outlineof Main
Stage
Theoverall
composition
isoutlined in theblockdiagnmsonpp.2-6.
r Tuner
Stage
o AM/FM Synthesizer
Stage
*MANUAL : Frequency changed in single steps each time the TUNING UP or DOWN hey is pressed. Frequencies scanned
when pressed continuously, the scanning being stopped assoon as the hey is released.
*STATION SCAN : Frequencies scanned.when either TUNING UP or DOWN key is pressed. Scanning pauses
for 5
seconds when a broad.casting station b tuned, and stops altogether if the MEMORY/STOP key is pressed
within that 5 secondperiod. Otherwise, the scanning is resumed.,
*STATION SEARCH : Frequencies scanned when either TUNING UP or DOWN key is pressed, and stopped when a
broadcasting station is tuned.
sx-7 sx-6 sx-5 sx-4
l.D. MOS FET single-stageRF
amplifier plus twin vari-cap
tuning circuit (equivalent to
4-ganged tuning capacitor) in
FM front-end.
Sameas
SX-7
J-FET single-stage
RF amplifier
plus twin vari-captuning circuit
(equivalent to 3{anged tuning
capacitor) in FM front-end. Same
as
SX-S
PLL lC stereo decoder stage SameasSX-7 Same
as
SX-7 Sameas SX-7
Vari-cap tuning circuit (equiva-
lent to 2-gangedtuning capaci-
torl in AM tuning stage
and AM
tuner lC lLA1247l.
SameasSX-7 SameasSX-7 Sameas
SX-7
sx-7 sx-6 sx-5 sx-4
lmproved S/N ratio achieved
by
pulse-swallow system for FM
reception.
S/N ratio 80dB(Mono)
75dB (Stereol
Same
as
SX-7
S/N ratio 8od8(Monol
75dB(Stereo)
Same
as
SX-7
S/N ratio 75dB(Mono)
TOdB(Stereo)
Same
as
SX-7
S/N ratio 75dB(Monol
70dB(Stereo)
Frequency memory (presetting)
capability for up to 8 stations
in
eachband. Same
asSX-7
Frequency memory (presettingl
capability for up to 6 stations
in eachband.
In models including two AM
bands(LW and MW),any LW or
MW frequencies may be stored
in the 6 AM memories.
Same
asSX-5
3 tuning
modes:
MANUAL
STATIONSCAN
STATION
SEARCH
Sameas
SX-7 2tuningmodes:
MANUAL
STATION
SCAN
only the sTATloN scAN
tuning mode isavailable.

o Amplifier Stage
o Display
Stage
sx-7 sx-6 sx-5 sx-4
Equalizer
amplifierfeatureslow-
noisetwin FET ICL differential
amplifier in first stage,and oper-
ational amplifier (lC) in second
stage
for MC cartridges.
S/N ratio 8OdB(MM)
67dB(MC)
Equalizer
amplifier
features
low-
noise transistors differential
amplifier in first stage.and oper-
ational amplifier (lC) in second
stage.
S/N ratio 79dB
Operational amplifier (lC)
euqalizer
amplifier.
S/Nratio 70dB
Sameas
SX-S
S/N ratio
Microcomputer
controlled
elec-
tronic switching lC (PA40O8l
for function
selector. SameasSX-7 Same
asSX-7 Same as
SX-7
Microcomputer controlled VCA
lC(PA5O04) volume control
features 32-step control, pre-
settable levelsand audio rnuting
(-2sdBl.
Sameas
SX-7
Conventional volume control
with variable resistor. Same
asSX-5
Non-switching amplifierem-
ployed
in power amplifier
stage.
Output
power 60W+60W
l2OHz-20kHzl
Rateddistortion O.009%
SameasSX-7
Outputpower 45W+45W
(20H2-20kHz)
Rated
distortion 0.OO9%
Sameas
SX-7
Outputpower 30W+30W
l2OHz-20kHzl
Rateddistortion O.O2/"
Conventional class B ampli-
f
ier
Output power 20W+2OW
l2OHz-2Ok{zl
Rateddistortion O.O4%
sx-7 sx-6 sx-5 sx-4
s-digit
LED numeric
displayof
tuned
frequency. Sameas
SX-7 Same
asSX-7 16-point scale LED display of
tuned frequency.
LED numeric display of elec-
tronic volumecontrol levels. Sameas
SX-7 Not featured in SX-5 Not featured in SX-4
LED numeric display of time
(built-in
quartz
clock function). Not featured in SX-6 Not featured in SX-S Not featured in SX-4
6-point LED display of output
power. SameasSX-7 Not featured in SX-5 Not featured in SX-4
3-point
LEDSIGNALindicaror
indicating signal strength of
tunedfrequency. Same
asSX-7 TUNED indicator to show that
broadcast station has been
tuned.
SameasSX-5

TunerStage
O I.D.MOSFET
The FM front-end RF amplifier in model SX-?
(and SX-6) featuresan I.D. MOS FET (ion-implan-
tation dual gate MOS FET) - P001 manufactured
by PioneerSemiconductor Laboratory. The major
featuresof this FET - P001 include high gain,Iow
noise, Iow distortion and low IM (P.G. 25dB/
100MHz,N.F. 2dBl100MH2,
I.M. -54d8/107dBp)
as a result of an extremely accurate short channel
obtained by a "self aligning" operation involving
a "local silicon oxidation" process.Furthermore,
a O.4p narrow channel (1/3rd to 1/5th the width
in normal components) has beenachievedby the
ion-implantation double diffusion construction.
Use of this FET in the FM front-end greatly
assistsin improving sensitivity and reducing inter-
ference.
o Pulse-SwallowPLL
Synthesizer
When the VCO (Voltage Controlled Oscillator)
frequency is very high and the CMOS progmmm-
able divider operating frequency is exceeded, the
PLL will cease to function. Two methods are
presently available
to resolvethis problem. In one
of these methods (the fixed divider system), an
ECL (Emitter to Emitter Coupled Logic) prescaler
is positioned in front of the programmable
divider.
And when, for example, a 1/10 prescaleris em-
ployed to obtain 25kHz step frequencies, the
referencefrequency will be 2.5kHz. This frequency
is very low and cannot be adequatelyremoved by
the low-pass filter. As a result, signal components
are leaked into the mixer leading to deterioration
in the S/N ratio. This is one of the main dis-
advantages
of the fixed divider system.
The other method available
is the pulse-swallow
system which employs a specialfrequency divider
called a "two-modulus prescaler" instead of the
prescaler used in the fixed divider system. In this
method, a 25kHz step synthesizer will generatea
25kHz reference frequency and a 50kHz step
synthesizer will generate a 50kHz reference
frequency, resulting in a much higher S/N ratio
than in the fixed prescalersystem.
The pulse-swallow
systememployed in the SX-7
is incorporated in an IC (M54922P) controlled by
microcomputer.
Amplifier Stage
o Non-SwitchingAmplifier
(SX-7,
SX-6,SX-s)
In non-switching amplifiers, the output stage
transistor biasis controlled on the basisof class B
operating point in order to maintain the operation
within the operating region (between cutoff and
saturation) and thereby suppressthe generation of
switchingdistortion.
The basic non-switching amplifier circuitry is
outlined in Fig. 1-2. To simplify the diagram,
transistor Vgn and diode Vg, E1 and E2 are
assumedto be 0.6V and the transistorbasecurrent
is disregarded.While no input signalisapplied,the
voltage drop across R5 and R6 may also be dis-
regarded.And if the voltageacrossR1 and R2 due
to idle current is ignored, the voltages at different
positionswill beasshownin the diagram.
When an input signalis applied, a voltage will be
generated
acrossRt by NPN stage
(Q1/Q3) oper-
ation during the positiveportion of the signal.This
voltage is applied to the Q5 emitter-follower
(voltage gain of about 1) resulting in almost the
same voltage being generated across Rb. This
voltage is then added to the output stage bias
voltage. Hence, the PNP stage(Q2/Q4) maintains
the same bias conditions as when no signal was
applied, which meansthere is no cutoff. Likewise,
the NPN stagemaintains the samebias conditions
during the negative portion of the signal as when
no signalwasapplied, againeliminating any cutoff.
Fis.
1-1 Pulse
swallowsystem
I
Fig.
1-2 Basiccircuitryof Non
SwitchingAmplifier

Gontrol Stage
The incorporation of microcomputers in these
receivers has further simplified operational
procedures. The PD6007 (SX-7) and PD6004
(SX-6, SX-5 and SX-4) ICs are both basicallythe
same 4-bit microcomputer (with 2k-bit memory
capacity), the main differencelying in the software
program. Whereasthe PD6007 incorporates
a clock
function, the PD6004 featuresa 2 band (LW/MW)
AM tuner switchingfunction.
The PD6007 and PD6004 pin configurationsare
shownin Fig.1-3.
E
Xlol
Xlol
REEEi
tRo
so
sl
sczro
T'
ro
Pr
P2
Pr
Oo
Ol
Oz
U3
O5
O6
V3s
KI
K2
Kl
KO
STBY
Fia
Rr5
Rr2
Htl
Rto
Re
RE
R7
R6
d5
R4
R5
R2
Rr
RO
Fig.
1-3 Pin configurationof PD6007
(PD6004)
iSET
rRo
SF
5U
fp"
I
IP.
I
l"'
LPo
l-xo
I
l*'
l*'
LKo
TC
Rl3
Rt2
[-n,r
I
I R'o
1""
LRe
t l-nz
I
LR6
R5
R.
AF MUTE IND R3
VOL.MEMORY R2
VOL. lND. Rr
f"o
VOL.
OATA I ^-
ourPUT | "'
lo"
loo
Lo.
fo.
DArA l^-
our PUT
| "'
lo'
Loo
EXTAL
CLOCK
INPUT
KEY INPUT
CLOCKINPUT
(5OOHz)
SCANSTOP
MUTING
OtIT
P.O.DATA
/
o)4.,,
INPIJT
5-TH
DIGIT
o oR5
ol _ _ M54s22P
! |5""i'- aM/
AJ cPs RE.ET
PA4@€l
c4 Fil
C3 AM
c2 PHOilO
C{ A'XIVID€O
i]"",,
:,.':,,,"
.," FUIICTION
SELECTfi IC
10
Fig.1-4 System diagram
of controlsection
(SX-7)

o Synthesizer
Control
Fig. 1-5 outlines the tuner-related computer
operationcommand input key matrix.
Key
description
9k/10k : AM-MW band frequency step switch.
ON for 9kHz steps,andOFF for 10kHz
steps.
9k/1k (PD6004) : AM-LW band frequency step
switching. ON for 9kHz steps,andOFF
for lkHz steps.
TUNING AUTO/MANUAL : ON for auto tuning
(x1),andOFF for manualtuning.
SCAN/SEARCH : ON for short-time hold search
(x2), and OFF for operation according
to TUNING AUTO/MANUAL switch
(*6).
FM : Display of tuned frequency by single
push(*3), and pin 16 of synthesizerIC
(M54922P\ switchedto L level(x4).
AM : Display of tuned frequency by single
push (*3), and pin 16 of synthesizerIC
(M54922P) switchedto H level(x{).
LW/MW (PD6004) : LW-MWswitching with each
push.
M1 - M8 : T\rned frequency presetting keys. Cor-
responding STATION indicator lights
up (*5).
TUNING UP,DOWN : Frequencytuning keys.
MEMORY/STOP : Memory store enable key.
STATION indicators (1 to 8) and the
PRESET STEPindicator blinks on and
off for 5 secondswhen pressed
once.
A broadcasting station and volume step
may be stored in memory during this 5
second period. And when pressed
during frequency scanning,the scann-
ing operation ishalted.
EL,E2 : Switching for different regions (USA,
Europe etc.) Wired up according to
regionwithout switching.
81, B2 (PD6004) : FM IF offset adjustment.
(*1) Station search where frequencies are scanned by
pressing ?UN/NG UP or DOWN key once. Scanning
stops when broadcaststation frequency is tuned.
(*2) Station scan where frequencies are also scanned by
pressing TUNING UP or DOWN key once. Scanning
pauses for 5 seconds when broad,casting station
frequency is tuned. Scanning will be resumed after
the 5 second pause unless the MEMORY/STOP hey
ispressed.
(*3) 16-bit serial d.ata from the SO pin is sent to the
frequency display d,riuer IC (TD6301P), conuerted
to 7-segment decimal data by transfer cloch (output
from Pg and P1 pins) for driuing the LED numeric
display.
LOCKSW. NON-LOCK SW.
IlnAnjJ
Fig.
1-5 Switch
keymatrixfor synthesizer
control
(*4) The data transfened to M54922P contains 2O bits.
These are diuided into 5 groups of 4 bits each by the
4 pins Rg to R1y The transfer output clock is
obtained from R6 and R7. The first 4 data items
(16 bits) are used in programmable diuider frequency
diuision, while the Sth data item (4 bifs) is used for
operation mode designation.
(*5) BCD encoded data from pins Og - Og is applied to
the BCD to decimal decoder IC (M74LS42P). Pins I
to 9 (excluding pin 8) correspond. to Ml to M8, and
are switched to L leuel resulting in the LEDs being
lit up.
(*6) Actual circuits are wired so that the K6 line to the
SCAN/SEARCH switch is cut when the AUTO/
MANUAL switch is in the MANUAL position. The
SCAN/SEARCH switch will be operatiue only when
in the AUTO position.
NON
- LOCKSW.

r Function
Selector
Control
The computer operation command input key
matrix for function selector control is outlined in
Fig.
1-6.
Key
description
PHONO : Pin 10 of the IC (M74LS42P) refened
to above(*5) is switched to L level(*7), and
volume steps are displayed (00 - 31) in the
LED numeric display.
AUX : Pin 11 of IC (M74LS42P) switched to L
level (x8), and volume step alsodisplayedin
LED numeric display.
FM: Pin 16 of IC (M54922P)switchedto L level
asdescribed
above(x9).
AM: Pin 16 of IC (M54922P)switchedto H level
asdescribed
above(x9).
LW/MW (PD6004) : AM band switching.
CLOCK (PD6007) : Time displayed in LED
numeric display when pressed
1x19;.Display-
ed time is adjusted by TUNING UP and
DOWN keys while the CLOCK key is depress-
ed. In the SX-7, time is displayedaslong as
the POWER switch is left in the STD-BY
position.
(*7) L leuel here results in PHONO indicator being
turned on, and the PHONO channel of the elec-
tronic switch (PA4008) used by the FUNCTION
selector aleo being turned on.
(*8) L leuel here results in the AUX indicator plus the
IC (PA4008) AUX channel being turned on.
(*9) Depending on whether pin 16 of IC (M54922P) is
at L leuel or H leuel, and the leuel of pin 10 (L
leuel for PHONO) and,
pin 11 (L level for AUX) of
IC (M74LS42P), the AM-FM switching circuit is
actiuated, the AM or FM indicator tumed on, and
the IC (PA4008) AM or FM channel switched ON.
(*10) A 500H2 pulse signal obtained by diuiding the
crystal oscillator signal (source of the synthesizer
reference signal) appears at pin 17 of IC (M54922P),
and is applied to the TC pin of PD6007 to actiuate
the cloch functions.
r Volume Control (SX-7 and SX-61
Models SX-7 and SX-6 havebeenequippedwith
an electronic volume control IC (PA5004). This IC
hasthe following 4 functions.
1. The gain is changedfrom -90d8 to OdB by
changing the voltage on the VOL terminal
(pin 12)from 0 to 3.2V.
2. The balanceis changedcontinuously from right
channel only (-bV) to center (0V) and left
channel only (+5V) by changing
the voltageon
the BAL terminal (pin 9) from -bV to +5V.
3. Audio muting of approximately -25dB is
applied when the MUTE terminal (pin 11) is
switchedto L level.
Fig.
1-6 Switch
keymatrixfor function
selector
Fis.
1-7 Switch
keymatrix
for volumecontrol

4. Loudness as determined by a twin T-shaped
filter connected between pin 3 (6) and pin 5
(14) is activated when the LOUD terminal
(pin 7) isswitchedto L level.
The operation command input key matrix for
the VOLUME control isoutlinedin Fig.1-7.
Keydescription
VOLUME UP, DOWN : Increase
and decreaseof
5-bit electronic volume control data
(*11). 32 positionsare available
(00 to
31).
MUTING :Audio muting switch(*12).
VOLUME PRESET : Memory switch for the elec-
tronic volume control steps positions
(32 positions
from 00to 31).
MEMORY/STOP : Memory store enablekey. A
single push enables VOLUME position
and STATION frequency to be stored
in memory during a 5 second period.
(*11) The S-bit output data from Oa - OZ and Rgpins is
conuerted f'rom digital to analog data by ladder
resistor and applied to pin 12 of PA5004.
(*12) The Rg pin isswitched alternately to H and L leuels
each time this switch is pressed. This H/L leuel is
applied to pin 11 of PA50O4, the L leuelresulting in
actiuation of the muting circuit.
o Other Terminals
R4
Switched to L level when the electronic
volume control position (00 - 31) isdisplay-
ed. The VOLUME indicator iscontrolled by
this signal
(SX-?and SX-6).
Switched to L level when the VOLUME
PRESET key is pressed
once, and when the
MEMORY/STOP key is pressed,
L level and
H level are switched alternately for a 5
second
period. The PRESETSTEP
indicator
iscontrolled by this signal.
Switched to L and H level alternately each
time the MUTING key is pressed. The
PA5004 audio muting operation (-25dB)
and the MUTING indicator are both con-
trolled by this signal.
Switched to L level during time display by
PD6007.The colon (:) in the time display
is
controlled by this signal
(SX-7).
And with the PD6004, this pin is switched
to L and H levelsalternately during frequen-
cy scanningoperations,the signal beingused
to turn the TUNED indicator on and off
(Sx-5 andSX-4).
R5 :Switched to L level when 50kHz unit
included in the FM tuning frequency (during
tuning mode where FM frequencies are
changedin 50kHz steps).This signal
controls
the "0" and "5" in the 5th digit position
(10kHz unit) in the FM frequency display.
And with the PD6004, this pin is switched
to L level when the LW band is selected
(in
models equipped with 2-band AM tuner
section).
R6 :Synthesizer IC (M54922P) control output
(data transfer clock I). Data transfer is
commenced by the trailing edge of this
signal (i.e. the moment that the pin is
switchedto L level).
R7 : Synthesizer IC (M54922P) control output
(data transfer clock II). Data readingtiming
signal.The M54922P readsdataby synchro-
nizing with the trailing edgeof this signal.
R8, R9, R10, R11 : Data output and key inputs
applied toM54922P.
RL2 :Muting output. Switched to L level for
about 1 secondwhen PHONO, AUX, FM
and AM (LW/MW) key is pressed. Also
switched to L level (for about 0.7 seconds)
when the Ml to M8, TUNING UP or
TUNING DOWN key is pressed. These
signalscontrol the electronic switching IC
(PA4008) in order to suppressswitching
noise.
Rl-3 :Scanningoperation stopped when an H level
input signal is applied during STATION
SCAN or STATION SEARCH tuning mode.
Input of detector signal from tuner section
tuning detector circuit.
Memory Hold
Model SX-7 is equippedwith an auxiliary power
supply circuit used to supply the microcomputer
with power irrespective of the POWER switch
position. In this way, the microcomputer RWM
(read write memory) contents can be preserved
for about 2 weeks when the AC mains power is
completely switched off. The clock function is
inhibited in this case.If the AC mains power is
left off for more lhan 2 weeks,the RWM contents
will disappear, and will therefore have to be
rewritten if the memory isto beusedagain.
The RWM hold period in the SX-6, SX-5 and
SX-4 models when the POWER switch is left off
is about 3 days. When two new size "AA" dry
batteries areused,however, memory contents can
be maintained for several vears.
R1
R2
R3

The RWM hold period in the SX-7 has been
extended by inhibiting the microcomputer (con-
sumption current is lessthan 10pA). And in the
SX-6, SX-5 and SX-4, the battery life haslikewise
been extended in much the same way. This
inhibition operation is controlled by the I-EQ-and
STBY terminals. The switching sequenceinvolved
in switching to inhibit mode must follow the order
shown in Fig. 1-8. Normal memory functions are
lost once the inhibit mode Vcc drops below 2.5V.
Note that the RIESETterminal hasto be at H level
during inhibit mode. Furthermore, approximately
lmA of current is consumeduntil cessationof the
clock pulse input (Extal).
Although the switch on sequenceduring restart
has not been specified, the reset signal is applied
only after all prescribed values have beenretumed
to normal. Fig.
1-8 Power
supplysequencefor inhibit
mode