Sherwood S-9400 User manual

SHEFR\ATOOD
LOW FILTER
Whendepresged
reduces
rumble
fromturntable
andlow
frequency
noise.
(Attenuatesat
12db/octave).
SELECTOR
coltTRoL
Selectsyour
stereolistening
source:
PHONO
1,
PHONO
2/
MIC,TUNER,
AUX.1,AUX.2.
MoDEL
5-9400
sTEREO/DYNAQUAD
AMPLIF
IER
5ERVICEMANUAL
0
$
r
L\
ILLUTIilATED
SELECTOR
IIIDICATOR
Describes
position
of
selector
swltch.
BAtJAIiICE
Balanceethe
relative
volume
levels between
your rightand
leftspeakers.
SPEAKERS
S€lects
your
main stgreo
speakers
(A),
remotestereo
speakers (B),
both sets,or
turnsspeakers
off (for
headphone
listening).
IODE SWITCH
Permits
listening
to leftchannel
only,right
channel
only,
stereo,reverse
or
mono-through
bothspeakers.
touDNEss
Masler power
ON/OFF
and
volume
control
foryour
speakers.
Also
automatically
add bass
compensation
at low levels.
LOUONESS
Whendepressed,
defeats
loudness
control
compensation
circuit (which
automatically
increasesbass
tonesatlow
volume
levels).
HI FITTER
Whendepressed
cuts off scratch
from records,br
background
"hiss" trom noisy
FMstations.
(Attenual* at
12db/octave).
TAPETOI{ITOR
Permits
recording
to,or
(depressed)
playingback
fromtape
rscorder;
permits
monltorlng
duringrecording.
BASS TREBLE
Increasesbass lncreases treble
tonesupto *12 tonesupto *12
db,decreases db,decreases
upto -12 db. up
to -12 db.
TAPE
DUBBING
Permits
recordingto, or
playing
back
from,a second
taperecorder.
Also,permits
dubbingfrom
one recorder to
theother.
SPECIFICATIONS
PHO]IEE
Forprivate
listening
with
stereo
headphones.
FOUR
CHATTINEL
Controls
special
rear
panel
inpuls
andoutputs
for
a4 channel
decoder(may
alsobeusedas
asecond
tape
monitor).
InputSenrltlvfi (forrated
output):
Phono,
1.8mv.
Auxiliary,200
mv,
Mic.,2.1
mv
Input
Gapabllity
lor 1olo
dist.:
Phono,80
mv.
Auxiliary,
lnfinite
Mic.,60mv
Hun andl{oise
(lHF}:
Phono
-60 db.
Aux.
-85
db.
Vol.
Control
Min.
-90
db.
Crosrtalk:
-45
db @ 1KHz.
tlc. Inputlmpedance:50,000
o
GENERAL:
PowerRequiremenb:
1
1
5-1
25V,50/60Hz.20-200
watlstused.
AGOutletr:
Switched
(2)
total180
watts.
Unswilched
(1)
200
watts.
Slze:
(X)"
H,OOo
W,
00" D.
Shlpplng
Welght:
29lbs.
DYITIAOUAD
Controls
built-in
Dynaquad
4 channel
matrixingcircuit.
Power
Oulput:Music
power
160watts
total
(lHF)
RllS Power
Outpul
(both
channels
driven):
60wattsx2@4
ohms,l KHz
50
watts
x2 @ 8ohms,1KHz
40watts
x2 @
8ohms,20-20,000
Hz
Harmonic
Dlstortlon:
0.8oloI ohmrated
output,
0.10o/o
@10
watts.
lnlermodulation
Dlsioilldn
:
0.60/o
@
8ohmrated
output
,O.25o/o
@
10watts.
SlereoandlllonoSpeaker
Outpullmpedance:
4,8,
or16
ohms.
StereoHeadphone
Output:Highorlowimpedance.
StereoRecording
Output:230
mv,2K
ohm.
Power
Bandwidth:
5-45KHz-l
o/o
Dist.
Frequency
Rerponre:
Aux.
20-20
KHz
-t-y2 db.
Phone:
RIAA
Std.
i 1.0
db.
Damplng
Factor:
40:1
@
I ohms.
Bass
Conlrol:
-f-
12db.
@
100Hz.
Treble
Conlrol:
+ 12
db@ 10KHz.

TR509 TR504
R525 VR501
PRE-AMP
BD
TR701b
TR701a
cB
52
c8s1
c853
c8
54
DUPLICATESON
OTHER
DRIVER
BD.
TR50B
I
R6241TR505
TR702
VR7O1
TR704
TR7O5
TR7O6
T
R7O3
TR902b
TR9DZa
TR901b
Page2 Figure 1
TR901a

NOTE:
5-9400 AMPLIFITR
SERVICING
AND
ADJUSTMENT
To simplify the following descriptions only the left channel
and its related circuitries are described. The right channel
is identicaL except for reference symbol numbers
o (
See sche-
matic diagram
) nff reference numbers refer to Figure I unLess
otherwise specified. .
PreLiminary checks of the DC voltages present at various
points in your amplifier can indicate whether a transistor is
oPen, shorted r or otherwise malfunctioning. Fault isol-ation
in the preampfifier, tone amplifier, and driver stages ean
generaffy be isolated by checking the DC voltages. Many times
the circuit defect can be isolated by comparing gain measure-
ments at lKHz as indicated on the schematic or by comparing
the operating channel with the defective channe.l-.
AMPLIFIER
TLECTRONIC
RELAY
PROTECTION
AND
SPEAKER5YSTEM
CHEIK5:
This amplifier incorporates a special eLectronic over.load pro-
tection circuit which automatically disconnects the speakers
when danger to the power amplifier exists or when danger to
the speaker system exists. If there is no output to the speakers,
check the speaker connections for shorted wires or shorted
speakers. (
Sp"aker line resistances should not indicate less
than 4 ohm resistance on an ohmmeter.
)
The Electronic Re1ay Protection circuit consists of an eJ.ectronic
switch which senses two eonditions, output current and DC center
point voLtage, to protect both the power ampl-if
ier and the
speakets. This circuit limits the current delivered to the
speaker load and also protects the speaker from DC vol-tages in
the event of an amplifier device failure. A center point DC
shift is detected by dif f
erential- ampl-ifier TR702 and TR703, which
disconnects the power amplifier from the speaker J-oad by way of
transistors TR704, TR705 and TR705, which deactivates a re1ay,
disccnnecting the speaker load. The power amplifier current
protection is obtained by transistors T
R701a and T R701b with
associated components, which sense the current through the output
transistor resistors R524 and R525. Vrlhen the peak currents
reach approximately 5 Amps, TR70l-aand TR701b conduct, causing
mul-tivibrator action in conjunction with TR704, TR705, and TR705
to deactivate the relay at a recurring rate, thereby protecting
the amplifier from abnormal-
load conditions. This circuit will
continuely sample and disconnect the spearkel line untiL the ovex-
load condition is removed.
While servicing the ampl-ifier it will be valuable to operate the
amplif ier using a variabl-e vo.l-tage
power Iine (
VARI
AC
) equipped
with a line wattmeter to identify abnormal power consumption.
I nerease the power line voltage upward while observing the
wattmeter. Power consumption should not exceed 10-2U watts
(
loudness control volume at minimum
) .s the voltage is increased
Page 3

to the rated I2O VAC. If the power
consumption
begins to
20 watts, do NOTincrease the line voLtage any further and
detexmine whether the malfunction is in the power
suPPfV
'
or amplifier section.
exceed
tuner,
If the power amplifier is suspected, verify the center point
voltage at the + speaker terminal for a ZERO
voltage + 0.2V
xeading. If the center point vo.l-tage
reads a plus voltage r
suspect a shorted top side driver transistor (TR604) or a short-
ed top side darLington output transistor (TR508) (schematic shows
transistors as the top devices in each channel). If the eenter
point voltage reads minus, suspect a shorted bottom side driver
transistor (TR505) or a shorted bottom side darlington output
transistor (TR509
).
A defect can frequently be located by removing both driver
transistors from their sockets. If Line power consumption drops
considerablyr suspect faufty driver transistots. If powelc
con-
sumption remains high faulty output transistors shoul-d be suspect-
ed. If not the pre-driver CIrassociated components may be
defective.
If the f aul-t sti1l exists, then verif y that capacitors are not
shorted, circuit board contains no sol-der shorts, open resistorst
poor solder connections, or broken pads.
If the center-point vol-tage reads zero voltage in accordance
with the above check, apply audio signal- to the channel or
channel-s being tested and measure distortion. Distortion which
exceeds amplifier ratings may be due to one of the following:
1. 0utput transistors are not beta matched.
2. 0utput bias requires readi ustment.
3. Driver transistors aIe not Ploviding adequate
s
ignal drive.
The following performance indicates a properly oper'ating amPlifier
with an I ohm resistive load.
Distortion at 2.0V:
Less than 0.15%IM or Harmonic
(tKHz), Typically O.O7/"
Distortion at 10V:
Typically A.2/oIM or Harmonic (
ff Hz
)
Typically 52 lrlatts DuaI Channel at 0.8/o (ZOHz ZOKHz)
Typically 50 tl/atts Singfe ChanneL
at O.8/o
Page 4

OUTPUTTRANSI
sTOR
BIAS:
Proper output transistor operation and output bias adj ustment are
most important to assure correct performance of the amplifiet.
Bias adj ustment is necessaxy if the output transistors are ne-
placed, * or if any of the transisto:rs in the driver circuitry r or
the ampLifier exhibits one or more of the following symptoms:
0verheating of the output transistors
under normal-
operating conditions.
Excessive Low leveL I ntermoduLation or
Harmonic Distortion more than B.15%
at 2.O volts across I ohms.
*It is extremely important that the mica insulating washers used
to seperate the output transistors from their heat sinks be un-
broken and installed properly with siLicon grease liberafly
applied to aLJ-
surfaces in contact with each other. Make certain
the emitter and base pins of the output transistors do not contact
any part of the heat sinks.
SUGGESTED
AMPLIFIER
TEST
BENCH
AUDIO
osc. SCOPE
+Probe
l.
2.
SET.
UP
D.C.
VOLTMETER
RECEIVER
AC
SWITCH
POSITIONJEST
RECPTS.
I.H.
D.MEASUREMENT
2. I.M. MEASUREMENT
3.SINE
WAVE
MEAS.
O
- 3OO
Wotts
WATTMETER
TO INPUT
JACKS TO
OUTPUT
TERMINALS+
VARIAC
60Hz
PHASE
ADJ.
6.3
VAC
t20v
60Hz
orc. fz<l
?u'.
iJ it
60db ATTENUATOR
lOdb Steps
[5 - r25VAC
O-,5Olblts
Fig
ure Z
Page 5

OUTPUT
ANDBIAS ADJUSTMENT
USING
AN INTERMODULATION
DISTORTION
ANALYZE
R
Connect the amplifier for testing similar to Figure 2.
Connect an Intermodulation Distortion Analyzer with a
ratio of 4:1 using 6OHzand 7000H2
to the ampLifier (AUX)
input and set the selector switch to AUX.
Set the volume control to maximum
and adj
ust the generator
f or an ampl,if
ier output of 2.O volts across B ohms.
4. lrJhile
observing the resultant distortion wavef
orm, adjust
the bias potentiometer (
VR501)so that the crossover
distortion is at a point of being eliminated. (Class ttAgtt)
Note: Class trAtr
operation (continued Clrrl
rotation) causes
output transistors to draw excessive current and overheat.
RTFER TO DIAGRAMSBELO!il
I.
2.
3.
lmproper Bios
Ad
iustmeni
Proper Bios
Adiustment
5. Repeat Steps 3 and 4 for oPPosit channel.
The following performance indicates a pxoperly operating
amplifier with an B ohm load.
Less than 0.15% IM Distortion at 2.OV
Typically O.2% IM Distortion at 10V
5O Watts of power per channel- at O.8%, single channel
50 h/atts of power per channel at O.8%, Dual channel
If an I ntermodulation Distortion Analyzer is not available r dF
0scillator and a Harmonie Distorticln Analyzer may be used for
adj ustment of the output transistor bias as foLIows:
l.
2.
Connect the amplifier for testing similar to Figure 2,
Connect an OsciLlator with less than .O5/"
distortion at
IKHz to the amplifier (
nUX
) input and set the selector
switch to AUX.
Pag
e 5

5et the volume control to maximumand adj ust the Oscillator
for an amplifier output of 2.O volts across I ohms.
Using the Harmonic Distortion Analyzer looking at the
distortion of the amplifier outputr properly nulled, make
the adjustment as fol-Lows: Adjust the bias for Class frABrl
operation by turning the bias potentiometer (
VR501
) so that
the cxossover is at a point of being eliminated.
Note: CIass rrArr
operation (continued Ch',
rotation) causes
the output transistors to draw excessive current and over-
heat.
REFERTO
DIAGRAMSBELOhI
3.
4.
lmproper
Bios
Ad
iusf
ment
Adjus
t t he bias pote
ntiomete
r
the amplifier begins to cause
wattage consumption.
at O,!yo, single channel
at o.8%, ZOHz
-20r
000H2,
Proper Bios
Adiustmenl
5. Repeat Steps 3 and 4 for the opposite channel.
The following performance indicates a properly operating
amplifier with an I ohm load @ lKHz.
Less than 0.10%
THD
at 2.0V
Typically 0.15%
THDat 10V
60 Watts of pobrerper channel
50 ldatts of powe r per c
hannel
Dual channel
can also be adj
usted by using a VARI
AC equipped with a
wattmeter:
Turn the loudness controJ- to minimum.
Bias
li ne
1.
2. (VR501),
to the point at which
a vexy slight increase in line
P
ROTECTI
ONBOARDTESTI
NG
AND
ADJUSTMENT:
Without audio drive.
1. Adj
ust VR701 for equal voLtage on the coLIectors of TR702
and TR703. The differential amplifier is now balanced so
as to properly prote.ct against + DC voltage at the sPeaker
te rminals .Page 7

2. Short the speaker terminals on both the Left and right
channel speaker outputs.
3
. Connect an audio oscill-ator opexating at lKHz to both
AUX inp uts ,
4. Now, test the protection board for proper openation by
increasing the audio drive leveJ- to the powex amplifiet.
This wilJ- cause the relay to be deactivated, disconnect-
ing the speaker terminals from the amplifier at a recurring
rate. This should occur at less than 100 watts of 1ine
input power. Do not audio drive into a short circuit,
buyond this input power 1eveL.
FOUR
CHANNTL
OPERATION
The 5-9400 incorporates a 4-channel matrixing circuit. This
simple matrixing circuit all,ows recorded ambient signals, which
are not reproduced during conventionaL stereo playback, to be
converted to 4-channeL sound without additional amplifing equip-
ment. By connecting 2 additional- speaker systems, one each to the
REM0TELeft and Right terminals, they then become the left rear
and right rear sound soulces with the front panel toggfe switch
in the Dynaquad I
N position.
hlhenthe toggle switch is in the rrupil
position the speakers
connected to the REMOTE
terminals can be util-ized as a second
set of stereo sound sources in the same area or at a remote
J-ocation.
Page I

PART
DESERIPTION
TRANS
I5TOR5
2N5087
2sA505L
2
5A
640
2sc593F
25C945P
2sc959L
25C1
000
25C121
1D
25032
3
K
25K34
cDE8002C
5P5
5456
DIODES
15188
1
s247
3
5V-03
u-05c
v05c
wz-1
20
CAPAEITORS
ELECTROLYTIE
4.7uf @
25U
4.7uf @25V (AXIAL)
10uf
@
15V
1
Ouf @25V
1
Ouf @
50V
33uf
@
5.3V
33uf @25V
33uf @
50V
41uf @
10V
1
00uf @ 25U
1
00uf @
50V
221uf @
50V
33Ouf @1
0V
1
000uf @
53V
4700uf @
50V
cAPACIT0RS,
TANTALUM
.47uf @35V
4.7uf @
15V
VARIABLE
RESI5TOR5
BIAs
ADJUsT
(1K)
S-9400PARTs
LIsT
SCHEMATIC
REFERENCENO.
TR501ar501b
TR505a,
505b
TR501
a,5O1b,
5O2a,5O2b
TR901
a
r9O1b
r912a,6OZb
TR704r705
TR503a,
503b,
604a,5O4b
TR503a,
503b
TR801
TR608a,
508b,
509a,5O9b
TR502ar
5D2b
TR705
TR7U1
a,701b
1702r7O3,
802
D701
a,701b
1702r7O3
r7O4
D501
a,
501b
D501ar501b
Dg01
,go2,803,804
D6O4a,
5O4b
r705,
805,
805'
851
D8
07
C501ar501b
,9O1
a
gOZb,903a
r
903b,
904b
C9D2a
C503a,503b,504a
505a,
505b
,
5O7
a,
c81
0
C508a,
508b
C504a
, 504b
,7
02
C6O2a
r
5O2b
C606a,605b'854
C505a,505b
c7
01
,901
b,
9O4a,
,504b,
507b
C51
0ar
510b
,5Olar507b
c801
,808,
809
c703
c8
53
cB
5
1
,852
C509a,509b
C
5U1
a,
501
b
2810001
I .85
PARTNO.
3
0200780
30000101
30000241
30200124
3020u521
3U2U0371
3020071
0
3
02
00421
3U300143
30400041
3U200531
3020u
590
30500260
30500410
306U01
80
30500450
30500u3u
30500370
6404347
5
541
1
347
5
640421
06
640431
05
6404s1
05
64040
335
54843335
5404s335
54A41
475
540431
07
6404s1
U7
54045221
54D41
337
542451
08
5424547
8
6605441
4
5606247
s
LIST*
PRICE
.90
2.go
.78
.98
.50
2
.10
-72
1
.17
4
.44
1
.26
1
.50
.30
.30
.22
.48
.38
.55
.90
.48
.48
.48
.48
.55
.32
.48
.52
.35
.56
I
.25
1.45
.
B0
3.00
6.30
.53
.85
VR501ar501b
Page 9

PART
DESCRIPTION
JARTABLE
RESIsT0Rs
(
C0NT.
)
DIFF-AMP
BALANCE
(IT)
BALANCE
C0NTR0L
(
nUnl 1
00K)
L0uDNEss
C0NTROL
w/swITcH
(DUAL
1
OOK)
TONE
CONTROLs
(
DUAL
1
OOK
)
GENERAL
SECTION
SWITCH,t4IC/PH0N0
2
SWITCH
, PRE-AMP
0UTIMAIN-AMP
SWITCH,LTVER
TYPE
SWITCH,M0DE
SWITCH,SPEAKER
SWITCH,SELECT0R
LAMP
(
8V-0.
1 AMP
)
LAMP
(
EV-O.25
AMP
)
THERMISTOR
D-224
FUSE
3A
MECHANICALSEETION
MICROPHONEJACK
HEADPHONE
AND
TAPE
DUBB
I
NGJA
CK
INPUT
BD. (,| JACK)
I
NPUTBD. (q JACK
)
INPUT
BD. (E JACK)
INPUT
BD. (,|O
JACK)
DINJACK
(S PIN)
SPEAKER
TERMINAL
BD. (A POST)
FUSE
HOLDER
A.C. OUTLET
FUNCTIONGLA55
(
CNII-OUT5)
TRANSF0RMER,
P0l^lER
TRANSIST0R
SUCKET,
Pob/ER
THERMISTOR
HOLDER
KN0B,LARGE
W/l4ARK
KN0B
, sMALL
bJlMARK
KN0B,
SLI
DEC0NTR0L
KNOB,
FLIP LEVER
EsCUTCHEON
l,'100DCABINET
FEET,
PLASTIC
POLYETHYLENE
BAG
sTYREFOAM
ENDCAPs
cART0N,
SHIPPING
SCHEMATI
C REFERENCE
NO.
VR7O1
VR551
ar551b
VR552a,552b
VR901
a
r9O1b,
9
O2a
r9O2b
5W2
SbJ9
5h/3r4r5r6rgr11
s!d7
5tif1
0
st|J1
PL1
,213r4r5
PL1
rl
TH501
a,501b
F1
LIST*
PART
NO. PRICE
IN
2810004I
2820001
1
280000
53
2800
0040
2730000s
27300005
27
50001
2
27100040
27
1
0D044
27100051
37008016
3700801
9
30700010
38300030
33020700
33030400
3
301
0'l00
33040500
33080300
331
00300
34034001
53080200
34032001
3
40428D1
200s4001
3s90008
5
34011002
531
52001
29058001
29056001
29
1
07
002
291060s?
1009
1001
85034002
74A14001
81100013
89048001
85083001
.50
2
.24
4
.40
2.go
1
.44
1.26
1.95
2.34
2.34
4
.O4
.53
.66
.12
.30
.96
1
.2D
.60
1.58
2.50
2
.68
.90
3.1
0
1
.25
.50
3.66
29.95
.54
,24
1
.20
.95
.86
.55
19.75
22.80
.24
'48
6
.26
*NOTE:
Page
I
0
PRICES
SUBJECT
TO
CHANGE
h,IT
HOUT
NOTI
CE
.

MAIN AMP IN
VR9Ole 6
I@KBX2 &
| | ^-^ TR6Oh TR602r TR6OA TR6O5. t
H i..*tr 25A6{0 . 25A640 zscese 25A606 |
_ | .*^ r2s^666)
(2sA666)
(?lq?SCl.
12!4!3?) |
oJ (2scllz{) (2sA706)
sw-sl I
L______.1
o o 8w-roRoH
o-o x
CIRCUIT
DIAGRAM
sw-9L
3015
TONE CONTROL BOARD
r---TnToi"----'--
o
o
o
ooo
sw-7
r___J
6008MAIN AMP BOARD
r-- R66.
iT'-'
F
-{F
s'*
z
:
t
--
7
=
=3
f --iR
?'+
F*
P
IST
Ff
3
ooo
o swtd o
()
J
d
tl
t-
o
Irl
&
()
G
d
ti
t-
a
&
o
F
-
0
J
J
U
z
{
SHERWooD
S-9400
STEREOAMPLIFIER
7O5T
PROTECTION CIRCUIT BOARD
f-_----.]
tl
sw-10
SP SELECTOR.
I. OFF
2.4
XB
{A+B
942-l
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