先锋PIONEER SA-8500II音响电路图
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(Dr:roruecn
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sA-a5C,Cltr
^
MODEL SA-8500IICOMES
lN FOUR VERSTONS
DTSTINGUISHED
AS FOLLOWS:
r e
A
This service manual is applicable
to the Ku-type. When reparing the KC-type, Hc'type or S-type,
please see the additional service manual.
CONTENTS
l .
2.
3.
4.
5.
6.
7.
8.
1 1
1 1
12
1 6
1 8
l 9
20
CONNECTION
DIAGRAM
SPECIFICATIONS
BLOCK DIAGRAM
5,2
Tone Controls
LEVEL DIAGRAM
5
6
7
9
13
14
1 5
21
22
23
24
FRONT PANEL FACILITIES
CIRCUIT DESCRIPTIONS
5.1
EqualizerAmplifier
a.*r:
5.3
Power Amplifier
5.4
Protection Circuit
5.5
Power Supply Circuit
PARTS LOCATION
8.1
Front Panel View
DISASSEMBLY
8.3
Top View
8.5
Rear View
ADJUSTMENT
4.2
Front View with Panel Removed
8.4
Bottom View
9.
10.
Type
Voltage
R€marks
KU
120V only
UL {U.S.A.) approved
KC
120V only
CSA (Canada) approved
H G
22OV and 24Ov (Switchable)
SEMKO (Sweden),
NEMKO {Norway}, DEMKO (Denmark)
and El {Finland} approved
s
1 1OV . 12OV . 22Ov and 24OV { Sw itch able }
General export model
t\
EXPLODED
VIEWS
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11. SCHEMATIC
DIAGRAMS.
P.C. BOARD PATTERNS
AND
PARTS LIST
11.1 Miscellanea
11,2 Schematic Diagram .
11.3 Switch Assembly (AWS-108)
11 .4
Phono Jack Assembly (AWX-I07)
1 1.5
Equalizer Amplif ier Assembly (AWF-023)
1 1.6 Control Amplif ier Assembly (AWG-044)
11.7 Power Amplif ier Assembly (AWH-05I )
12. PACKING
- l
32
33
35
41
42
46
50
53
-
)a
@
\
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I
)
1. SPECIFICATIONS
Semiconductor
T r a n s i s t o r s
. . . . . 4 7
D i o d c s . .
. . . . . . 2 9
Power Amplifier Section
Circuitry .
2-stagc
differenrial
amplifier parallcl
PP direct-coupled
OCL.
Continuous Power Output form 20 Hertz to 20,000 Hertz
(Both channels driven) . . 60 watts per channel (8 ohms)
75 watts per channel (4 ohms)
Total Harmonic Distortion at 20Hertz to 20,000Hertz
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 t
. . . .
0 . O 5 o / o
3owatts per channcl
power output,8ohms . . . . 0.01y.
I watt per channel
power output, 8ohms . . . . . . 0.01%
lntermodulation
Distortion
Continuous
rated power output
. . . 0.05%
3owatts per channel
power output,8ohms . . . . 0.01%
I watt pcr channel
power output, 8ohms . . . . . . 0.01y.
Frequency
Respon5c
.. . . . 5Hertzto 100,000Herrzl0,dB
lnput (Sen
sitivity/
lm pedance)
P O W E R A I \ 4 P l N
. . . . .
. . . 1 V / 5 O k o h m s
O u t p u t . .
. . S p e a k e r :
A . B , A + B
Preamplifier Section
Circu itry
Equalizer
amplifier: lst stage differential amplifier 3-
stage direct-coupled A class SEPP.
Control amplifier: lst stage differential amplifier 2-
stagc direct-coupled,
NFB type.
Input (Sensitivity/l
mpcdance)
PHONOl .
. . 2.5mV/50kohms
PHONO2
. . . 2.5mV/50kohms
CARTRIDGE LOAD. . . . . Both PHONO I and 2, 100,
200,300,400pF
T U N E R .
. . 1 5 0 m V / 5 0 k o h m s
A U X . . .
. . 1 5 0 m V / 5 0 k o h m s
T A P E P L A Y 1 . . . . . .
1 5 O m V / 5 O k o h m s
T A P E P L A Y 2 . . . . . . . .
l 5 0 m V / 5 o k o h m s
PHONO Overload
Level (T.H.D. :0.05%)
P H O N O
L
. . . 2 5 0 m V ( 1 k H z )
P H O N O 2
. . . . 2 5 0 m V ( 1 k H z )
Output (Level/
lm pedance)
T A P E R E C 1 . . . . . .
1 5 0 m V
T A P E R E C 2 . . . . . .
. . . . . . . . . ' l 5 0 m v
PRE OUT
lv/2kohms, 6V/2kohms (Max.)
Total Harmonic Distortion
( 2 0 H 2
t o 2 0 , 0 0 0 H 2 )
. . . . . .
. . . . . o . o 2 . A
Frequency Responsc
PHONO (RIAA Equalization)
TUNE R, AUX, TAPE PLAY
F i l t e r
L O W . . . . . . . . . .
H | G H . . . . . . . . . .
Loudness
Contou r
(Volume control set at
sA-a5ClC'II
20Hz to 20,000H2
t0.2dB
. 5Hz to 50,000H2
j ? d B
Tone Control
BASS...
... r10dBl25Hzl5l9zll01Hz)
TU RN OVER frequency
1Q0Hzl200Hzl4O0Hz
TREBLE.
...i10d8(8kHzl'l6k9zl32k1z)
TURN OVE R frequency
2kHzl4kHzlSkHz
. . . 1 5 H z ( 6 d B / o c t . )
. . 8kHz 16d B/oct.)
40dB position) : +6dB (100Hr)
+ 3 d B ( 1 o k H z )
Hum and Noise
(lH F, short-circuited,
A network)
P H O N O .
TUNER, AUX, TAPE PLAY . . .
l \ 4 u t i n g
. .
M iscellaneous
Power Rcquiremcnrs
120V 60Hz only.
Powcr Consumption
l80watts (UL)
390VA (CSA), 490watts (Max.)
Dimensions
. a20(W) x 150 (H) x 376 (D) mm
16-9116
x 5-118 x 14-13116
in
Weighl
. . Without Package:
13.9kg (301b l0oz)
With Package: 15.8kg (341b 13oz)
Furn ished Parts
O p e r a t i n g
I n s t r u c t i o n s
. . . . . . . 1
C o n n e c t i o n
C o r d
w i t h P i n P l u g s
. . . . . . . . 1
Hcx. Wrench (Used for fastening Volume Knob) . . . . . . 'l
NOTE:
Specificotions ond the design subject to possible modifica-
tion u,ithout notice due to improuements.
. . . 7 5 d 8
. . . 95dB
0 , 2 0 d 8
I
Headphone: Low impeddnc
c
r
Damping
I dclor (20Hert1
lo 20.000Hcrt./,
8oh m:) . . . 30
Hum and Noise (lHF, short-circuited,
A network) . . 110d8
!
p
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2. CONNECTION DIAGRAM
TU RNTABLE 1
T U N E R
TU RNTABLE 2
' r ' l
C A R T R I D G E
T A P E P L A Y E R
TAPE DECK 2
J
-n
Connect to
ground terminals
etc.
GROUND
LEA D
G R O U N D I N G
TO EARTH
F
@
A S P E A K E R S Y S T E M
B S P E A K E R S Y S T E M
I
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3. FRONT PANEL FACILITIES
BASS TURN OVER SWITCH
Selects
the frequency
below which the BASS controt tonc
adjustments
apply. Ser swirch to 100H2, 200H2 or 40OHz
according
to listening room and speaker
system character-
istics or personal
preference.
TONE SWITCH
ln the ON pos;tion, tone adjustments
can be performed
with the BASS and TREBLE controls. When set to the
upper (OFF) position, the tone control circuits are dis-
engaged
and frequency response
is flat. This function is
convenient
for checking
phono cartridge
and speaker
tone
quality and listening
room acoustics.
Set to ON position to energize 54-850011.
After setting to
ON, there is a brief delay before sound is obtained. This
is due to the operation of the muting circuit which
prevents noise when the PowER is switched. This func-
tion does not indicate difficulty and normal operating
condition is attained in a few seconds.
The POWER switch
also controls the rear panel SWITCHED convenience
outlets.
PHONES
JACK
When listening with stereo headphones,
connect them to
this jack.
NOTE:
Set SPEAKERS switch to OFF when listening only with
headphones.
SPEAKERS
SWITCH
Selects speaker system operation.
OFF:
Sound not obtained from speakers
(when using
headphones).
A:
Sound obtained from speakers
connected to A
speaker
terminals.
B:
Sound obtained from speakers
connected
to B
speakers
terminals.
A + B :
Sound obtained from speakers connected to
both A and B speaker
terminals.
NOTE:
When listening with headphones or to temporarily inter-
rupt the speaher sound, set switch to OFF or to an
unused speaher position.
BASS AND TREBLE CONTROLS
Controls for adlusting
low and high frequency tones. With
the TONE switch set to ON, turning the BASS control
clockwise
from center enhances
the frequency band below
the point selected by the BASS TURN OVER switch,
while counter-clockwise
rotation attenuates this band.
In a sinrilar manner, the TREBLE control adjusts the
frequency range above the point selected
by the TREBLE
TURN OVER switch.
TREBLE TURN OVER SWITCH
Selects the frequency above which the TREBLE control
tone adjustments apply. Set to 2kHz, 4kHz or SkHz
according to listening room and speaker
system character-
istics or personal preference.
t ' - " " 1
LOW FILTER SWITCH
Set to 15Hz position in the event that turntable rumble.
recording cutting noise or other low frequency noise
becomes ob jectionable. Attenuation in the frequency
band below 15Hz is 6dB/octave.
HIGH FILTER SWITCH
Set to 8kHz position if record scratch noise or other high
frequency noise becomes objectionable.
Attenudtion in
the frequency
band above 8kHz is 6dB/octave.
BALANCE CONTROL
Control for adjusting
stereo balance
between left and right
speaker systems or headphones.
Turn clockwise from
center to increase
right (R) channel volume and counter-
clockwise from center to increase
left (L) channel volume
in order to obtain a balance.
VOL
Adf us
atten u
arbitr
b inati
wider
CART
Switc
match
I
t--
I MUfl
I Switc
I contr
I volu
I the n
I contr
IILLOUDN
When li
enhan
numa
switchc
7
POWER
SWITCH
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lones.
With
SS control
)and below
5R switch,
this band.
idjusts the
E TREBLE
LE control
z or 8kHz
I character-
f'-"''r
able rumble,
uency noise
e frequency
rr other high
tenuition in
left and right
ckwise from
and counter-
lnnel volume
CARTRIDGE LOAD SWITCH
Switch for selecting phono circuit
match the load capacitance of the
input capacitance
to
employed cartridge.
VOLUME CONTROL
Adlusts speaker and headphone
volume. Scale indicates
attenuation in dB with maximum volume assigned
an
arbitrary value of 0dB. Control can also be used in com-
bination with the MUTING switch to Drovide a finer and
wider range of adjustment.
sA-A5Clcltr
FUNCTION SWITCH
Selects
desired
playback program source.
PHONO 2: To play records on a turntable connected
to
the PHONO 2 jacks.
PHONO 1 : To play records on a turntable connected
to
the PHONO 1 iacks.
TUNER:
To listen to broadcasts
with a tuner con-
nected to the TUNER iacks.
AUX:
To play a component connected
to the AUX
iacks.
TAPE MONITOR SWITCH
Employ for tape playback or to monitor a recording
in
progress.
1 :
Playback or monitoring of a tape deck
connected to the TAPE 1 jacks.
SOURCE: Be sure to set to this position when not
using the tape deck for playback.
2:
Playback or monitoring of a tape deck
connected to the TAPE 2 iacks.
NOTE:
When listening to records or broadcasts, be sure to set
this switch to SOURCE. Sound will not be obtained
from speahers if set to I or 2.
TAPE DUPLICATE
SWITCH
Employ when using two tape decks for duplication or
editing. Be sure to set to the OFFposition at other times.
1 --> 2:
Duplication of tape from TAPE 1 (playback
mode) to T APE 2 (recording mode).
O F F :
)
T ' " - ' - l
(0 rrrorueen
I E R E O
A M P L
$A-8500
[
MUTING SWITCH
Switch for reducing volume by 20dB from the VOLUME
control setting. Convenient for temporarily reducing the
volume when changing
records
of tapes, since it eliminates
the need for continually read
justing the VOLUME
control.
OUDNESS
SWITCH
When listening
at low volume settings,
set switch to ON to
enhance low and high frequencies.
The response
of the
human ear to sound differs according to loudness.
This
switch compensates
for this effect at low volumes.
Set to this position when not using the
duplication feature (this includes
simultane-
ous recording with two tape decks and tape
playback).
Duplication of tape from TAPE 2 (playback
mode) to TAPE 1 (recording
mode).
SWITCH
Reverses
left and right channel stereo signals
and reproduces
them stereophonically.
2 - 1 :
MODE
R E V :
STEREO: Set to this position for normal stereo repro-
duction.
L + R:
Mixes left and right channel signals and
reproduces
them monophonically.
L:
Left channel signal is reproduced mono-
phonically
from both speakers.
R:
Right channel signal is reproduced mono-
phonically
from both speakers.
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4. BLOCK DIAGRAM
Ssa o
S+a-d ' TAPE MONITOR
1 . T A P E I 2 O F F
3. TAPE 2
S s a - c
, X 0 D E
1 R E V
3 . L r R
. 5 R
2 STEREO
I
o n c c
I P O w
BA SS
PRE
T R E B L E
CONTROL
AMPLIFIER
l
L
PR
PO
t t
SV'JITCH
ES ,
S r a - d ' F U N C T I 0 N
t . P H 0 N 0
2
3 T U N E R
S z o , b , C
S E L E C I O R
1 . 1 0 0 p F
3. 300pF
S 3 o - d , D U P L I C A T F
l . l * 2
3 . 2 * 1
sqc
s+a
Ssa
VRza,b , BA LANCE
V R r a , u ' V 0 L U I I E
6 VRru
c ^
r b o , b
Sra,
s
Sao,
u
Sso,
o
Stoo,
u
' IlUTI NG
: T O U D N E S S
' H I G H F I T I E R
' LOW FILTER
. T O N E
' S P E A K E R
] O F F ?
3 B
4 .
OFF - -20d8
OFF
_. ON
O F F
- B k H z
OFF 15 Hz
OrF - 0N
A
A + B
S r z R E L A Y
S 1 3 . P O W E R O F
S 1 a ' B A S S T U R N 0
I 1 0 0 H 2 7 . '
a
/ ^ ^
|
J . . t L r u l . ' 1 7
S l 5 , T R E B L E
T U
1 . T k \ z
l .
3 B k H z
PHONO 1
PH(')NO
2
A U X
TU N FR
L E F T
C H A N N E L
R I G H T
CFIANNET
EQUALIZER
AI'lPLIFIER
"l -"
1 t 1v
TAPE |PLAY
L R E c
- PLAY
TAPE 2
L R E C
J
q ^ ^
Sno
5+u
"
9
o 6 b I
I vRto
I
cJ2i)
.PLAY
TAPE 1. R E C
. PL A'l
TAPE 2L R E C
2 . Pr-10N0
1
4 . A U X
2 2 0 0 p F
4 . 4 0 0 p F
2 . O F F
EQUA
LIZER
AIlPLIFIER
CONTROL
AHPLIFIER
4 L
Srra-a
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. R E L A Y
.. POIIER OFF - ON
. B A S S
T U R N O V E R
1 . l 0 0 H z 2 . 2 0 0 H 2
3 . 4 0 0 H 2
T R E B L F
T U R N O V E R
1 . L k H z 2 . 4 k l , z
3 . B k H z
PO
r -
WER AI1PLTFIER
L
PROTECTION
CIRCUIT
To pnotection clr^cuit
To pnotection
cir cuit
T o e q u a l i z e r ^
a m p
To con f r-o I amp
T o p o w e n a m p
r
To L ch powen ampl
proteclron cir cuit
e g u a l l z e n a m P
Contr0 I amP
T
To R ch powen amp L
eu 9 o
cJIo o
8a
ls
IT
J
T FIER
LEFT
CHANN EL
I
I
R I G
H T
C H A N N E L
f
rloru,s
SPEAKFR
A
? e
* "sb
I
eISeu
T
I
)-
PRE OUT
POWER
IN
To pr otection
cir-cuit
;
ce 1 3
CP
AC LTNE
S r z
Srs
au 1 4
r 0
To
To
i
I
I
,
POWER AIlPLIFIER
Srs
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A
5. CIRCUIT DESCRIPTIONS
z=50Krt
c)
c=roopr
PHONO
2
PHONO I
CARTRIDGE
LOAD SWITCH
sA-El5ClClII
-vcc
+
lr.
rl
Fig. L Schematic diagram of equalizer amplifier
, l i
5.1 EOUALIZER AMPLIFIER
The circuit diagram for the equalizer amplifier is
shown in Fig. 1. The two separate phono inputs
are selected by the FUNCTION selector on the
front panel. The input capacitance on the PHONO
terminals can be adjusted to 4 different levels
(100pF, 200pF, 300pF, and 400pF) by means of
the CARTRIDGE
LOAD
control knob which
switches in, or out, additional capacitors in parallel
with the input terminal. Hence, the load capaci-
tance of the phono cartridges can be changed,
greatly effecting the cartridge's frequency response
in the high frequency range, and thus providing
considerable variation in its characteristics.
The first stage of the equalizer amplifier (Q' & Qr)
is a differential amplifier using PNP transistors. The
next stage (Q.) is a bootstrap circuit employing C' ,
R1 to provide high voltage gain. The output stage
(Qo & Qr) is a complementary-symmetrical SEPP
circuit, whose high voltage utility factor results in
a high output voltage. This gives the equalizer
amplifier a very wide dynamic range, and an over-
Ioad input level of 250mV (RMS at lkHz) with no
more than 0.05% distortion.
The equalizer elements (Cr, C.,, R, and R.) consist
of polypropylene film capacitors (tolerance 127o),
and metal frlm resistors (tolerance t1%). Phono
equalizer RIAA deviation has been reduced to less
than 10.2dB (2OHz - 2OkHz\.
5.2 TONE CONTROLS
Incoming signals are amplified to the required level
by the 2 stage amplifier which uses a differential
amplifier at first stage. The tone control circuit is a
collector-base negative feedback circuit (NFB) and
features 3 tumover frequencies for both bass and
treble.
The basic principles of the NFB type tone control
circuit are outlined in Fis. 2.
'fl
h
rl
0d0ut
hI|lt
n, vn, n,
L.-
, , ,
-{P
c .
R l
, c . d
Fi1. 2.
t ,
v R , R ,
Basic circuitry of NFB type tone control circuit
iri
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Midrange Operation
The Cr and C, reactances are considerably smaller
than VRr at frequencies above midrange, effec-
tively shorting VRr. At frequencies below mid-
range, C. reactance becomes large and in effect,
opens the circuit. Consequently, the circuit be-
comes equivalent to that shown in Fig. 3 with
respect to the midrange. In this figure, the circuits
parameters are not changed by any change in pos!
tion of the VR, and VR. sliders. The NFB amount
is therefore fixed and the circuit gain is also fixed
without regard to VRr and VR, slider positions.
Fig. 3. Midrange
operation
of NFB type
tone control circuit
Low Frequency Operation
The reactance of C, and C, increases at low fre-
quency to form a circuit as shown in Fig. 4. This
ipactance increases in proportion to the frequency
declines. Also, the NFB amount varies grea y
according to VR1 slider position. The circuit sain
at low frequencies can therefore be varied by Vh1.
Capacitance of C1 and C, is changed by BASS
TURNOVER switch (by adding a capacitor to each
in parallel). This a.llows selection of the frequencv
at which VR, begins to take effect.
that shown in Fig. 5. C. reactance decreases in
the same de$ee that the frequency increases and
the NFB amount is now mainly controlled by the
VR, slider position. Consequently, the gain at high
frequencies can be varied by VR:.
C. capacitance is changed by TREBLE TURN-
OVER switch (by adding another capacitor in
series) to provide selection of the frequency at
which VR: begins to take effect.
Fiq. 5. High frequency operation of NFB type
tone control circuit
5.3 POWER AMPLIFIER
The circuit diagram for the power amplifier section
is shown in Fig. 6.
The input stage (Q1) constitutes a differential am-
plifier, employing a dual transistor (a 2-in-1 tran-
sistor "package" possessing the functions of 2
separate transistors). The second stage (er, e.) is
also a differential amplifier, but with the inclusion
of a current mirror (D1, Qr). Since the ea base-
emitter junction conesponds to a diode, the poten-
tial on the anode of D, and the emitter of eo will
be the same. Consequently, the potential drops
across R, and R, will a.lso be equal. So if the
resistance of these 2 resistors is the same, the same
current will flow through both sections. And if the
hpg of the transistor is sufficiently large, the base
current can be neglected. That is, the e. collector
current and the Qa collector current will be the
same. Since Q, and Q3 operate out of phase with
each other, Q: and Qo will operate as a push-pull
amplifier. The bias voltage for the power stage is
supplied by the potential difference produced
across VR1 - D3 - D, , where VR1 is the variable
resistor used to set this potential difference. D, is a
varistor which compensates for thermal differences.
The power stage (Qs- Q16) includes a 2-stage
Darlington connection, with the fina.l stage (e7-
Qto) forming two
complementary symmetrical
parallel circuits. The output mid-point is main-
tained at 0V by a balanced plus and minus power
supply and a 700% DC NFB circuit.
f
'l
vn.
Fig. 4. Low frequency
operation
of NFB type
tone control circuit
High Frequency Operation
The considerably smaller reactance of C, and C" at
high frequency in comparison with VR, effectivelv
shorts VR, to from an equivalent circuit such as
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-r
' ' r i
sA-aE'ootr
+vcc1
OUTPUT
+vcc2
INPUT
ft.'f
r\i'^
5.4 PROTECTION CIRCUIT
This circuit protects the power transistors in case
of overload, the speakers in case of power amplifier
malfunction, and also performs a muting function
when the power supply is tumed ON or OFF. The
protection circuit is composed of three sections
(Fis.7).
Por!r.r||0lili!r
Fig. 7. Block diagram of protection circuit
1. Relay Driver Circuit (Fig. 8l
The relay which connects the output circuits is
driven by this circuit. It also performs a muting
function to prevent unpleasant noise during ON-
OFF operation of the power supply as well as
opening the output circuit on command from the
detector circuits.
04
Fig. 6. Schematic diagram of power amplifier
Muting Operation
When the power supply is tumed .ON, Qu base is
reverse biased, through D6 and R26, turning Qo
OFF. Q? base potential rises as Ca charges through
R22 & Rz3, and Q? turns ON several seconds later.
The collector current of Q7 then flows through the
relay coil, operating the relay to tum on the power
amplifrer output circuit. The reverse bias of eu base
from Du & R2o disappears when the power supply
is set from ON to OFF. Qu remains ON however,
due to the residual power supply voltage. Ca very
rapidly discharges, Q, base potential drops and
Q? tums OFF. The relay releases and the power
amplifier output circuit turns OFF.
Note:
Q" is normally
OFF due to base bias and does not
participate in the muting operction.
{tr-
Fig. 8. Schematic
diagram
of relay driver circuit
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Operation by Detector Circuit Command
Command from the detector circuits pass through
one of D., Do or D, and are applied in the form of
a current flow. Q5 is normally reverse biased
through R1a, but when a large current flows
through on of these diodes, Q, base potential
declines according to the voltage drop at R,a.
Q, then becomes ON, Qu base potential rises and
Qu becomes ON. Co rapidly discharges and Q,
base potentia.l drops, tuming Q? OFF. The relay
releases and the power amplifier output circuit
becomes cut off.
2. Overload Detecto? Circuit
Shorting of the power amplifier load or a load
impedance below the specified value causes a
command to be sent to the relay drive circuit.
This is illustrated in Fig. 9.
Qa emitter is connected to Q, base through R, and
the junction point to Q, emitter. When RL is
extremely small, Iarge current flows in Qa, Q, turns
ON due to the RE, voltage drop, and current flows
in D.. C1 prevents faulty operation due to extemal
norse.
oirplifier
eq
Fig. 9. Basic circuitry of overload detector
3. Center Point Potential Detector Circuit
If a DC potential is produced at the junction point
of the power arnplifier, a command is sent to the
relay drive circuit. Fig. 10 shows this operating
principle.
Qr and Qo compose a differential amplifier. When
the same input is applied to both input terminals
(Q. and Qo bases), no output is present. However,
if there is a difference between the terminal inputs,
the difference is amplified and becomes the output
between the two collectors. During normal opera-
tion, an AC signal only is present at the junction
point. As Cr reactance is sufficiently low, the signal
is not applied to Q3, resulting in an absence of
output at the collector sides.
When a DC potential is produced at the junction
point, it becomes the input of Q. only. If the
voltage is negative, Q. collector current declines.
And at Qo the collector current increases and the
potential drops, causing current to flow through
If the DC voltage is positive, Q. collector current
increases and the potential drops, while at Qo the
collector current decreases and the potential rises.
Current therefore flows through D. .
Fig- 10. Basic circuitry of center point
potential detector
5.5 POWER SUPPLY CIRCUIT
The power stage provides voltage independently to
both left and right channels, using 2 separate
power transformers. Separate bridge rectifiers (one
for each channel) and 10,000gF (x 2) capacitors
provide the plus and minus voltages. Positive
voltage for other sections is provided by full-wave
rectification from the same winding on the power
transformer that is used for the left channel, and a
negative voltage from the corresponding winding of
the right channel transformer. Both are supplied
via voltage regulator circuits.
There is only one pair of secondary windings in each the
lcfl and righl channel powcr lrans[ormcrs.
{
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6. LEVEL DIAGRAM
siA-E'5clclil
SPEAKER
' t A
PRE OUT
PRE OUT
( 1 V )
-
-SPEAKEF
(23.7v, &) )
a m p 1 e r
f\il |
[*i
.D
1
d
J -
20
1 0
0
1 0
-20
30
50
- 6 0
27. 5dB
/Power l
\afn0lrlrer/
l
f
35.5dB
iEqual
zer \
\amplrfrer
/
r ( M u t i n g
O N )
17d B
APL. AU\
.r����������������0
5oB
/r5O,rV)
./
/Control \
\am plif re r /
(2. 5mv)
tzel
I r e r
FREOUENCY AT lKHZ
rtf
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7. DISASSEMBLY
Top Cover
Remove the four screws (A).
Front Panel
Loosen the setscrews of VOLUME knob with a
hexagonal wrench. Remove all the knobs by
pulling. Remove the four nuts (B).
Bottom Plate
Remove the ten screws (C).
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Control Amplifier Assembly
Remove the three screws (D).
Power Amplifier Block (L)
Remove the three screws (E).
CtA-E'5clC'tr
Power Amplif ier Block (Rl
Remove the three screws (F).
Equalizer Amplif ier Assembly
R€move the two screws (G).
Switch Assembly
Remove the seven screws (H).
1 7
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8.
8.1
PARTS LOCATION
FRONT PANEL VIEW
Knob (TR E B LE)
A A B . 1 1 6
Front panel
ANB.481
Knob (TONE)
A A D - 1 1 7
Knob {BASS)
A A 8 . 1 r 6
Knob (VOLU|\ilE)
A A B 1 1 4
Knob (CART R tDG E LOAD)
A A B 1 1 7
K n o b { F U N C T I O N }
AAB.1 1 5
;'ry;[
::|l
-iiq'
tr'
;l
(
o
Knob (POWE
R )
AAD-1 I7
Phone
jack (PHON
ES)
AKN-OO8
Knob (SPEAKERS)
A A B . l 1 6
. :
. . rF F
.,,,, .."., , ile5001
,l
.r"'.1
i l [
-.Frl -"F!
t n
]L.",,!
Knob (TApE)
A A D - 1 1 7
Knob (l\4ODE)
A A B . 1 1 6
Knob (MUTING)
AAD.1 1 7
Knob {LOUDNESS)
AAD.l 1 7
(
K n o b ( F I L T E R )
A A D . 1 1 7
Knob (BALANCE)
A A B . I 1 6
I
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I
8.2 FRONT V|EW WtrH PANEL REMOVED
SA-BSOOII
Rotary switch
(CARTR IDGE LOAD)
ASD,065 (ASD-055)
Rotary switch
( F U N C T T O N )
ASD,052
Lever switch (TO N E)
A S K 1 0 9
Variable
resistor
(BASS)
ACV 136
Rotary switch
( B A S S
T U R N O V E R
)
ASD 057
Rubber bracket
AEB-092
Rotary switch
( T R E B L E
T U R N O V E
R )
ASD.O56
Variable
resistor
(VO LU I\4 E)
A C V , 1 7 1
I
Variable
resistor
( T R E B L E )
ACV-136
a ) ,
)
' f ; . J r : '
a r , r , o , ,
'g)
tt E.E./.iJ
nno.(,
I T E.
n s l
Lever switch
(POWER)
ASK.1 24
Lamp with leads BV, 50mA
AE L 081
Phone
jack (PHON
ES)
AKN OOB
Rotary switch
(SPEAK
E RS)
ASD 054
Variable
resistor
(BALANCE)
ACV.l 72
Lever switch
(TAPE tVtON
tTO R)
A S K - 1
1 3
Lever switch
{TAPE DUPLICATE}
ASK,'l 13
Rotary switch ([4ODE)
ASD.053
Lever switch
it\,1uItNG
)
ASK- 1 1O
Lever switch
{ L O U D N E S S }
A S K 1 1 O
Lever switch
( L O W F I L T E R }
ASK 1 'IO
Lever switch
( H I G H F I L T E R )
A S K 1 1 O
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8.3 TOP VIEW
Equalizer
ampl ifier assembly
AWF-023
Variable
resistor
(VOLUI\4E)
ACV- r 71
Control amplifier assembly
AWG-044
Switch assembly
AWS.108
Power amplifier assembly
AWH-05'1
Power amplif ier assembly
AWH-051
Power transformer (L)
ATT.366
Power transformer (R)
ATT.367
Electrolytic
capacitor
10,000sF
50V
ACH-064
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siA-a50clu
8.4 BOTTOM VIEW
Ceramic capacitor
0.01s F 250V
ACG-001
Lever switch (POWER)
ASK-124
Switch assembly
AWS.108
Power amplifier
assembly
AWH.05I
Electrolytic capacitor
10,000l1F
50V
ACH-064
2 1
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8.5 REAR VIEW
Terminal {PHONO)
AKB-027
Terminal (SPEAKERS)
AKE,O26
Terminal (TUNER/AUX)
AKB-036
Terminal (TAPE 1)
AKB-035
Terminal (TAPE 2)
AKB-035
Terminat (PRE/POWER
AMp)
AKB.O35
Screw for ground (GND)
AKE.O30
AC Power cord
ADG-OO5
AC socket (AC OUTLETS)
AKP-OO4
2e
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-III
I
I e. ADJUSTMENT
I
I
The SA-8500 II amplifier employs the same type
I
of power amplifier assembly in both left and right
I
channels. Any adjustment will thus have to be
I
identical in both channels, and is limited to adjust-
I
ments of the idler current.
I
1'� Disconnect the jumper plugs, and terminate the
POWER IN terminats with b.1k0 resistors.
|
2. Connect 8Q resistors to the SpEAKERS A
terminals, and set the SPEAKERS switch to A.
3. Turn VRr in a fully counter-clockwise.
4. T\rm the POWER switch ON, and then readjust
VRr so that the voltage between terminals
sA-a5CtC'tr
E
o .
No. 3 (+) and No. 9 (-) reads B0mV.
Now check that the voltage between terminals
No. 6 (+) and No. 12 (-) reads 30mV 110mV
(in order to check the current distribution,
since the final stages are in parallel).
Leave the amplifier ON for about 30 minutes,
then repeat steps 4 and 5.
Finally, apply an actual signal, and check for
no crossover distortion.
7.
DC Voltmeter
@ :
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10. EXPLODED VIEWS
NOMENCLATURE
OF SCREWS.
WASHERS
AND NUTS
The following symbols stand for screws, washers and nuts as shown in exploded view.
Symbol
O€rcriplion
Shap6
RT
Erazier head tapping screw
PT
Pan head tapping screw
fF--n
\ l -
BT
Binding head tapping screw
F
CT
Counlersunk he6d tapping screw
TT
Truss head tapping screw
G-
ocT
Oval counterrunk head rapping
PM
Pan h6ad machine screw
CM
Countelsunk head h6chino
F
ocM
Ovalcountorsunk
head
F
TM
Truss head machine scrow
F
BM
Binding head machin€ screw
PSA
Psn hoad screw with spring
PS8
Pan head scr€w with spring
lock washer and tlat washer
PSF
Pan heed screw with flal washer
EXAMPLE
PM . 3x8
T T--'thinmm{,)
I
L-
diameter
in mm ( d )
,
Symbol
hr:r,
r.
n-"
Hr
(ol=
Symbol
EW
sw
N
WN
N u t
Washer faced nut
I ^
t -, q
@
$
F
tJ
fl
ITW
Interhal toothed lock washer
@
t
OTW
Outernal toothed lock washer
# l
Slotted set screw lCone pointl
E
D
Slotted set screw {Flat ooinr)
c E )
HS
Hexagon socket headless !€t
@ E )
ocw
Oval counlersunk head wood
cw
Count€rsunk head wood screw
Round head wood screw
-
Symbol
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Screw 4x8
ABA-079
@ . .
RT3xG
q
Front panel
ANB.481
Knob (TON E)
AAD.I 17
Washer faced nut M9
ABN-024
Knob (BASS)
AAB-I 16
Knob (TR EBLE)
AAB.1
16
l2n*,
\'nrY
o I
eartt
@A
Washer
taced nut Mg
-
t<.' \
-\
U,il
I
See page 22.
ABN.o24
*da\
\o
^ m" I
Knob(PowER)
\ \ )-"
^
K n o b ( P o w E R )
\
\ ) - "
AAD-1 17
\l/
9'�
\
\.r_/ o550
-
,
v
g'"' .. a,... -. ."t ..
'a*'",.-'t".,-'
rt/'
'!
A-
.."
.'t
.'/
.'/
'/
.'/
/
//
aQ)
Washer faced nut M9
Knob(SPEAKERSI
ft Y
ABN-024
4A8.116
*
ao-^
Knob (FUNCTTON)
Knob
(FrLrER)
@ u^-
*noo
r6ARllioo,
.ooor
AAD.117
-o,o^^,
,.
Kif,+;fu;.;'
Knob (BALANCE)
-
@Aa
AAB.114
AA8.116
V
Washer faced nut M9
Knob (MoDE)
ABN'024
Knob {LOUDN ESS, MUTING)
AAB-116
Knob (TAPE)
A A D . l 1 7
%
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Part 3
See page 29.
Part 2
See page 28.
siA-a5ClCltr
NOTE:
Parts indicated in green type cannot be supplied.
Screw 3x8
ABA-OO2
Screw 4x8
ABA-OI2
Part 1
See page 27.
RT3x6
Screw 4xB
ABA.O12
Screw 4x8
ABA.O12
Foot
g
A E C - I 7 8
e
RT4x 15
t@)
€
'aced nut Mg
4
)roN)
E LOAD)
Foot
A E C - 1 7 8
RT4x I 5
Foot
AEC-178
RT4x15e
g
, L €
Screw 4x8
A8A-012
Foot
AEC.178
RT4x15
@r
4
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B
c
D
A
B
D
Part 1
NOTE:
Parts indicated in green type cannot be supplied.
Control amplif ier assembly
AWG-044
F u s e
3 A ( F U 1 , 2 )
A E K . 1 O 1
Shaft cover
AEC-305
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