Sherwood S 8800A Service Manual

Page 1

MODEL S-8800a ALL-SILICON SOLID-STATE
FM STEREO RECEIVER SERVICE MANUAL

MODE]. 8-880041 100 \VAITS
Serial No. R8110018 & UP

- . nmzmreamu

MODEL 5-88000 STEREO RECEIVER SPECIFICATIONS

AMPLIFIER:
POWER OUTPUT (4 OHMS): music power 160 watts
total, continuous power 50 watts X 2.
POWER OUTPUT (8 OHMS): music power 120 watts
total, continuous power 40 watts X 2.
HARMONIC DISTORTION: 0.3S%@SQ rated output,
0.10%@2 watts & 5 watts.
INTERMODULATION DISTORTION: 0.696123 80 rated
output, 0.15%(52 watts & 5 watts.
STEREO & MONO SPEAKER OUTPUT IMPEDANCE:
4, 8, or 16 ohms. .
STEREO HEADPHONE OUTPUT: high or low imped-
ance.
STEREO RECORDING OUTPUT: 500mv, 2K ohms.
POWER BANDWIDTH: 12-30KHZ @1% Dist.
FREQUENCY RESPONSE: Aux. ZO-ZOKHz i1 db. ,
Phono: RIAA Std. i1.5db.
DAMPING FACTOR: 40:13 8 ohms.
BASS CONTROL: ¢15 db 5 40 Hz.
TREBLE CONTROL: 15 db515 KHz.
HIGH FILTER: -23db.:r 20 KHz. , -3 dbfl 5 KHz.
INPUT SENSITIVITY (for rated output): Phono, 1.6
mv, variable to 50mv. , Aux. 200nm. , Tape Monitor,
200mv.
INPUT CAPABILITY for 1% dist.: Phono, 250mv.y
Aux. 2.5 v.
HUM AND NOISE (II-IF):

Phono-65db.

Aux. -80db.

Vol. Control Min. -90db.
CROSSTALK: -40 db 61 KHz.
SPECIAL FEATURES: Mono speaker output, transis-
torized instant overload protection, Tone control flat
response : 5 degrees, Front-panel tape dubbing jack.

TUNER:

FM SENSITIVITY (IHF): 1.8uv (-30db noise & dist.)
SIGNAL-TO-NOISE RATIO: -70db.

CAPTURE RATIO: 2.0db.

SUPPRESSION OF AM: -50db.

TUNING RANGEi 87.5 to 108.5 KHz.

DISTORTION: 0.15%.E 100% mod.
CROSSMODULATION REJECTION: -95db.
STABILITY: :10 KHz (j; .01%).

IMAGE REJECTION: ~80db.

IF REJECTION: ~90db.

ALTERNATE-CHANNEL SELECTIVITY: 55db.
STEREO SEPARATION: 40db.1d 1 KHz.

FREQUENCY RESPONSE: Mono, 20-20 KHz i 1 db. ,
Stereo, 20-15 KHz i 1 db.

ANTENNA: 300-ohm balanced or '75 ohm coax.
SPECIAL FEATURES: FET rf and mixer stages,
Microcircuit IF & Synchrophase Limiter, Flywheel-
assisted velvet tuning, Dial scale 7-3/4 inches long,
0.2MHz calibrations, Interchannel hush with front-
panel level adjust, Zero-center tuning meter, Noise-
protected automatic FM stereo/mono switching 811v.
GENERAL:

POWER REQUIREMENTS: 115-125v, 60 Hz, 30 to 160
watts fused.

AC OUTLETS: (1) 300W. switched, (1)300W. unswitched.
DIMENSIONS: 16-1/4 L X 14 D X 4-1/4 H.

SHIPPING WEIGHT: 27 lbs.

OPTIONAL ACCESSORIES: Oiled Walnut Cabinet (W8)
17 L X 14 D X 5 H, Walnut-grained leatherette Case
(Type D) 16-1/4 X 14 D X 4-1/2 H.

Page 2

FREQUENCY IN HERTZ
20 so Ion 1K 2K

AUDIO RANGE

:I , z
E 9
B 7 E
a D
,.
I»
~ 5 m mm WI
POWER AMPLIFIER RESPONSE
ourrur IN wn'rs (PEAK)
l O I1 K 10 40 no In

II
250 E
W
E :I
m x
a 4., g Conlinuous
g 2 Power Ompm
,30 ° vs. Dislortion
; g1 mama Ohms
# .uI é (Each Channel]
5 :
FM 3 I
E 5" snecnvnv {
K -6n RACTERISTIC °
.Ioo 400 II mm .
snzoumcv IN KILOHEITZ I,
I l l I In 10 lo 0
ouvrur m wnrs (HMS)

IODX MODUlAIION
DD! = [0V RM!

FM LIMITING
CHARACTERISTICS

IN D!
I I I

OUT")! VOLTAGE

;
3 ..

0.5 m 2,5 s In

as 50 mu no no II II sII Ion 25K mum
INVUT IN MICROVDUS Hot) n ANTENNA!

xi."

+

Dislorlion

4

25w INPUT

a'c'

IKIIV INPUT

.0
0|

0: ounuv vomaz
a

R

m
Divzcvol
RESPONSK

O

50%

, sxm)
nmumcv nonuunon

7.IM (/700on :4/I w/srnI PlE-EHPHASIS)

. . . .
FREQUENCY DEVIATION IN HERTZ

Intermodulution

IN HERTZ
soc 1K zI 5x Ich 20:

FREQUENCV
2

20 50 I00

lOUDNESS CDNYROL
cmumcrsmsncs

REALIGNMENT: To check alignment, refer to page
3. Do not attempt realignment unless adequate test
equipment is available.

Optimum FM alignment, similar to the original factory
alignment, consists of feeding a properly-terminated
FM signal into the antenna terminals. To simulate a
balanced 300 -ohm input with the typical low -impedance
single-ended generator, connect a 120-ohm carbon 1/2
watt resistor from each generator terminal to a re-
ceiver FM antenna input terminal. While observing
the IF response curve with an oscilloscope through an
RF PROBE, carefully adjust IF transformers, top and
bottom, for the maximum symmetrical response. Check
the bandpass for 150KHz flat top with 100% FM modu-
lation. With this bandpass centered on the oscilloscope,
repeat step 11 for a zero reading.

All Sherwood tuners are also adjusted and checked to
see that they meet 1/3%IM distortion at 100% FM. To
adjust, feed 60 Hz: 7KHz at 4:1 ratio into alow-distortion
FM generator. With FM generator rf signal at 100%
FM, feeding into antenna terminals, read IM distortion
at FM detector output with receiver tuned for zero
volts. Adjust primary of T6 for minimum distortion.

Page 2

FREQUENCY IN HERTI
20 so me zoo 500 II 2x 5x max
.25

.20

44

9

..s *4
s

.m

an

I3 Is
III
E
U 0
III
D
*5
RECORD AND TAPE EQUALIZATION
-'° cunucvsmsncs
*I.
20
rasausncv m Menu
20 50 IOD 200 500 ll 2x 5x IO( 20K
920 i
\
34:5 ;\\ L I0"
3
.0 I I «V
\ // -
\ \\ /

DECIEELS

o

/
\§
/

\_4
\/
\\\\/ _

TONE CONTROL AND
FILTER CHARACTERISTICS

IA\/

III IIIIIII [