Sansui 771 User manual

771
This service manual is designed for service engineers to repair,
adjust, maintain and order the replacement parts of the 771 correctly.
When ordering the parts, use the stock number and parts name speci-
fically referring to the Parts Locations & Parts List.
For
general
usage
and
maintenance
of
the
unit,
please
refer
to
the
Operating
Instructions
attached
with
the
unit.
TABLE OF CONTENTS
Section
Title
Page
1,
:
SPECIFICATIONS
«605053.
5cen
se
ean
eee
sine
cageweeet
een
Peet
2
2.
BLOCK
DIAGRAM
AND
LEVEL
DIAGRAM
..............--------
3
94.-
“Block:
Diagram:
.csnwresduee
outages
vasasen
er
er
eeeeae
Oy
2-3;
.
‘Vevel
Didgtam:-
246
cfas0es
Motes
Meade
dee
esas
eG
esas
wel
ne
4
3.
THREADING
OF
DIAL
CORD
..................-2
2.
cece
eee eee
ees
5
4.
ALIGNMENTS
AND
ADJUSTMENTS
.............----.-0
0s
sees:
6
4-1,
Driver
Circuit
Board
Adjustment
...........--..2
ee
eee
ee
eens
6
4-2.
FMIF
Alignment..........
0...
eee
eee
ee
ete
eee
eee
ene
es
7
4-3,
FM
Dial
Calibration
and
RF
Alignment
...........--+++++--
7,8
4-4,
FM
Signal
Meter,
Mono
Distortion
and
Muting
Adjustment
....
8
4-5.
MPX
Alignment
.........ccce
cece
erence
eee
e
rene
een
eter
enee
9
4-6.
AM
IF,
Dial
Calibration,
RF
and
Signal
Meter
Alignment....
9,
10
5.
TROUBLESHOOTING
CHART
..............-.
6.
eee
e
eee
eee
ees
11
5-1.
Troubleshooting
on
Power
Supply
Section
..........-..+++-.
11
5-2.
Troubleshooting
on
Audio
Section
..........
6...
eee
e
eee
eeee
11
5-3.
Troubleshooting
on
Tuner
Section
..........--++
+++
eee
ee
11,12
6.
PARTS
LOCATIONS
AND
PARTS
LIST
............--.----+5--
13
6-1.
F-1479D
Tuner
Circuit
Board............
00
eee
eee eee
13,14,
15
6-2.‘
F-1504
Mic
&
Tone
Control
Circuit
Board............-...555.
15
6-3.
F-1503
Equalizer
Circuit
Board.........-.
2.
seers
eee
ee
eee
ee
16
6-4.
F-1505
Filter
Circuit
Board.
.......
0...
ccc
ccc
c
ener
eer
e
ee
eeee
17
6-5.
F-1490
De-emphasis
Circuit
Board
........--..
ss
eee
e
eee
17
6-6.
F-1499A
Driver
Circuit
Board
...........
0c
eee
eee
ee
eee
17,18
6-7.
F-1500C
Power
Circuit
Board
...........0
eee
eee
eee
eee
19,
20
6-8.
Other
Parts
(Front
Side)....
6.0.6...
cece
eee
eee
eee
eee
21,22
6-9.
Other
Parts
(Top
Side)
..........
sce
e
ere
e
cence
eee
eee
n
eee
23
6-10.
Other
Parts
(Bottom
Side)........
ec
cece
cece
eee
ete
eee
eee
ee
23
7.
SCHEMATIC
DIAGRAM
OF
TUNER
SECTION
..............-...
24
8.
SCHEMATIC
DIAGRAM
OF
AUDIO
SECTION
..............-..-
25
Q:
PACKING
LIST
cciscicc5
6k
he
dcs
ari
iceeie
dienes
ea
eae
26
10.
ACCESSORY
PARTS
LIST
...............
20:
cece
eee
teen
ees
26
11.
MAINTENANCE
..............0-..
000
eee
e
ee
eee
een
eens
26
11-1.
Voltage
Adjustment......
6.60.6...
c
eee
eee
eee
eens
26

1. SPECIFICATIONS
AUDIO SECTION
POWER OUTPUT (at rated distortion)
MUSIC POWER (IHF)....-- 140W (420 1,000Hz)
110W (8Q, 1,000Hz)
CONTINUOUS POWER
(Each Channel Driven). .55/55W (4 1,000Hz)
45/45W (8Q 1,000Hz)
(Both Channels Driven). .40-+-40W (8Q 1,000Hz)
32+ 32W
(8Q, 20 to 20,000Hz)
TOTAL HARMONIC DISTORTION
(at rated power output)
OVERALL (from AUX) ....less than 0.5%
INTERMODULATION DISTORTION
(at rated power output, 70Hz : 7,000Hz=4 : 1
SMPTE method)
OVERALL (from AUX) ....less than 0.5%
POWER BANDWIDTH (IHF) 15 to 40,000Hz
FREQUENCY RESPONSE (at 1 Watt power output)
OVERALL (from AUX) ....15 to 30,000Hz *7°5dB
EQUALIZATION (at TAPE REC output)
Piette aimee aes RIAA Curve
| (30 to 15,000Hz +1.0dB)
LOAD IMPEDANCE .......- 4to 160
DAMPING FACTOR ........ 60 (8Q)
CHANNEL SEPARATION (1,000Hz, at rated power output)
PHONO --4506.20/26e ¥esGe ds better than 45dB
AUN); 2 bas adacev ae better than 45dB
HUM AND NOISE (IHF)
PHONO sdexuicsGexaauns better than 70dB
ALC, Unis cracied es fies better than 80dB
INPUT SENSITIVITY AND IMPEDANCE
(1,000Hz, for rated power output)
PHONO: sa:cudeeeeneiks 2.5mV 50kQ,
(Max. input capability: 200mV at rated distortion)
MIC (monophonic) ...... 2.5mV 50kQ
POTD. coqtiatniaiiced auess 100mV 50kQ
TAPE-1
PLAY Pin Jacks ........ 100mV 50k,
REC/PLAY DIN Socket ..100mV 50kQ
TAPE-2 (4-CH ADAPTOR)
PLAY Pin Jacks ........ 100mV 50k
RECORDING OUTPUT
TAPE-1
REC Pitt: JaCKS: #.ccs50c0u 100mV
REC/PLAY DIN Socket ..30mV
TAPE-2 (4-CH ADAPTOR)
REC Pin Jacks .......... 100mV
SWITCHES AND CONTROLS
BASS sid tad ete thew Rae es +12dB at 50Hz
TREBLE ssatusns-en tere sees +12dB at 10,000Hz
LOUDNESS: sues 55464406 +10dB at 50Hz
+8dB at 10,000Hz
LOW FILTER ......-...... —10dB at 50Hz (6dB/oct.)
PLIGHAFILTER: onder ohwskas —10dB at 10,000Hz
(6dB/oct.)
TUNER SECTION
<FM>
TUNING RANGE .......... 88 to 108MHz
SENSITIVITY (IHF) .....-.-5. 2.0uV
TOTAL HARMONIC DISTORTION
MONO ak eee beens es 0.4%
STEREO wore edie ounet 0.6%
SIGNAL TO NOISE RATIO ..better than 60dB
SELECTIVITY: sonseSs: c3500% better than 60dB
CAPTURE RATIO .......... 2.0dB
IMAGE REJECTION ........ better than 75dB at 93MHz
IF REJECTION ..........45- better than 90dB at 98MHz
SUPURIOUS RESPONSE REJECTION
pals eee Lena aa better than 80dB at 983MHz
SPURIOUS RADIATION ....less than 34dB
STEREO
SEPARATION
......
better
than
35dB
at
400Hz
FREQUENCY RESPONSE ....30 to 12,000Hz *3:9d8
ANTENNA INPUT IMPEDANCE
Bape a auihyueds 3002 balanced, 75 unbalanced
<AM>
TUNING RANGE .......-.- 535 to 1,605kHz
SENSITIVITY
(Bar
Antenna)
..50dB/m
at
1,000kHz
SELECTIVITY
s2c4%
err
better
than
28dB
at
1,000kHz
IMAGE FREQUENCY REJECTION
uber Sule ape isatee better than 80dB/m at 1,000kHz
IF
REJECTION
.........-
better
than
80dB/m
at
1,000kHz
OTHERS
SEMICONDUCTORS
TRANSISTORS
.........---
49
DIODES.
susie
deca
biiae
sees
25
FETS:
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a
earn
ee
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cae
bata
Gem
panes
3
ZENER:
DIODES:
244.0
6%2No
es
4
POWER
REQUIREMENTS
VOLTAGE.
4auscoehaaades
100,
117,
220,
240V,
50/60Hz
CONSUMPTION
......-.-
100W
(rated),
310VA
(max.)
DIMENSIONS
..........065-
480mm
(18-74”)
W
135mm (5-34”) H
300mm (11-%6”) D
WEG
onctcine
vee
se
ties
12.0kg
(26.4
Ibs.)
net,
14.6kg (32.7 Ibs.) packed
*
Design
and
specifications
subject
to
change
without
notice
for
improvements.

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2. BLOCK DIAGRAM AND LEVEL DIAGRAM
2-1. Block Diagram
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POWER CIRCUIT
POWER
SIT.
$10: SP SELECTOR
$07; AUDIO MUTING S09: SELECTOR
S05: HIGH FILTER
$03: MONO
TAPE MONITOR-1
S01:
OFF
1.
OFF
ie
PHONO
2. FM
1.
OFF
1.
OFF
l.
STEREO
2. MONO
$04; LOUDNESS
1.
OFF
1.
ON
$12: DE-EMPHASIS
ON
$08: FM MUTING
ON
$06: LOW FILTER
ON
$02: TAPE MONITOR-2
AM
4. AUX-]
§. AUX-2
50uS
2. 75pS
1.
OFF
1.
ON
2. OFF
OFF
1.
OFF
2. ON
1
5. A+B 6. A+C
ON
ON
2-2. Level Diagram
* Each number (@, @, @...-) indicated in Level Dia-
gram
undermentioned
corresponds
to
the
number
in
Block Diagram.
1. MASTER VOLUME control ...........--: Maximum
2. BASS, TREBLE, BALANCE volume control ....Center
Se INPUE Sos cot encase PHONO 2.5mV 1kHz Sine Wave
AUX-1 100mV 1kHz Sine Wave
(output impedance of 600Q, at an
audio oscillator)
A QUtpUt. acca cadven 19V (45W) 80
Note: Each voltage value is for reference and measured
by a VIVM. In some recorders, the actual volt-
age value is in minor difference from the refer-
ence value.

3. THREADING OF DIAL CORD
* Length of dial cord...... approx. 150cm (59 inch)
If dial cord is cut or slips, replace cord by following
procedures. As 771 is used 0.6mm¢ cord, please replace
it with same type certainly.
3 turns
(Counterclockwise)
1. Threading of Dial Cord
Thread dial cord in numerical order from 1 to 16 as
shown in Fig. 3-1.
1)
Close the variable capacitor completely (Max. ca-
pacitance) and tie cord to number screw of the
dial pulley.
2) Thread cord in the direction of arrow from 1 to 3,
3)
4)
5)
then wind cord three turns around the tuning shaft
counterclockwise.
Thread cord in the direction of arrow from 4 to 12,
then wind it two turns on the dial pulley from 13
to 16.
After 16, tie cord to number @ screw of the dial
pulley.
* When you perform procedure 4) successfully,
please refer to the followings.
@To strengthen the dial cord tension, hold around
the end of cord and pull it toward the Front
Panel.
@Then, turn tuning shaft counterclockwise, as the
cord tension will be more constantly obtained.
@®Tie the cord to number @ screw of the dial pulley
(same as procedure 4) ).
After procedures, lock the knots of cord with paint.
2. Attachment of Dial Pointer
1) Close the variable capacitor completely.
2) Set the dial pointer to “0” on dial scale and insall
the dial pointer ass’y (See Fig. 3-2).
Fig. 3-2
Stock No. Description
6036050 Dial Cord (0.6mm¢)

4. ALIGNMENTS AND ADJUSTMENTS
Abbreviation
Equipment Others
AM FM Generator Oscilloscope...........- Genescope ClOCKWISE bcceeedcoudscrewatersareus sees CW.
AM Standard Signal Generator ............ AM SSG Counterclockwise...... ede Brenda ta nceier grate CCW.
FM Standard Signal Generator ............ FM SSG AMMA? ere Pow eed awe ncttale ch Ree aha ks ANT.
FM Stereo Generator...........eec cence eee Stereo SG MOO NATO es sa eticxTas os pends knedae de Xs MOD.
OstillOscOpe: sextet sess ee hdaee veankeyess Scope
Audio Oscillator >< svscxyndoxsetiswees eats Audio Osci.
Distortions Meter wiiecsusateseawe Sean ies Dist. Meter
4-1. Driver Circuit Board Adjustment (See Figs. 4-1, 4-2 and 4-3)
Note: 1. Master Volume......... eee eeeeee Minimum
2. Speaker Selector ..........eeeees SYSTEM (A)
3. Make the SP terminals free (no load).
4. Confirm the AC Power Supply voltage.
5. After adjustment, run the unit for more than 5 minutes, then check and readjust necessary.
6
. Room temperature should be 18~28° (65~83°F) for bias current adjustment.
STEP SUBJECT EQUIPMENT MEASURE OUTPUT | ADJUST | ADJUST FOR CONDITION
1
DC
OV
L-ch
DC
volt
meter
Speaker
terminal
F-1499
|
OV
+10mV
oStep
down
meter’s
range
L-ch VRO1 accordingly
(Fig. 4-7) o Change lead’s polarity if
meter swings backward
2 DC OV R-ch Same as above Speaker terminal F-41499 Same as above Same as above
R-c VRO2
(Fig. 4-1)
3
Bias
current
DC
milliammeter
F-1500
F-1499
19+1mMA
oStep
down
meter’s
range
L-ch FO1 VRO3 accordingly
(Fig. 4-2)
4 | Bias current Same as above F-1500 F-1499 Same as above Same as above
i R-ch FO2 VRO4
(Fig. 4-2)
Fig. 4-1 Fig. 4-2
milliam-
volt meter meter ©
mitliam-
meter
TLLLD PDO PLL
yf
ON LO
VRo2 VRo4
bias current DC OV DC OV bias current
volume volume volume volume

4-2. FM IF Alignment (See Figs. 4-8 and 4-9 on page 10)
Note: 1, Selectofs ..s%desede ss uve vevaswes FM AUTO
2. Master Volume ........eeee eee Minimum
3. Output level of genescope ...... After attenuator
4. Sweepwidth.........sceeeeeeene 1.5~2cm/150kHz
5. Frequency band .......s+sesee 9.5~11.5MHz
GENE SCOPE
6. Connection
eoaeneeernaeeaeese se aase
Connect the output of
genescope to TP.A through 100p ceramic capacitor.
7. Before adjustment, turn both VRO1 and VRO2 CCW (Max.),
VRO3 CW (Max.) and VRO4 to center.
IN
4.7kQ 10pF
DETECTOR PROBE BLOCK
FEED SIGNAL MEASURE
STEP SUB ADJUST ADJUST FOR CONDITION
| ESE | FROM | TO OUTPUT
1 IF coil Output 55dB Base of TRO1| Connected TO1,T02 | Max. IF wave- | oTurn core of T06
Genescope on F-1479 Point between form 1 as CC
(Fig. 4-9 R48 & R50 on Fig. 4-8
TP.A) F-1479
(Fig. 4-9 TP.B)
Use Detector
Probe ~°
2 Meter coil Same as above Same as Connected T06, TO7 Max. IF wave-
above point between from 2
R62 & VRO2 on Set the center
F-1479 of wavefrom 2
(Fig. 4-9 TP.D) with wavefrom
Direct from 1 as Fig. 4-8
Genescope
3 Descrimina- | Same as above Same as Connected T04 Max. linearity
tor coil above point between of S curve
R67 & R68 on TO5 Set the center
F-1479 of S curve
(Fig. 4-9 TP.C) wavefrom 1 &
Direct from 2 as Fig. 4-8
Genescope
4 IF coil Same as above Same as above } 103 Max. noise
4-3. FM Dial Calibration and RF Alignment (See Fig. 4-9 on page 10)
Note: Selector FM AUTO
. Master Volume Minimum
er ee meee e sears nee erase wreesewa
ee ere nese eeowre enn eone
vere em eee ne seers e sevens
. Confirm start point of dial pointer before alignment.
1.
2
3. FM Muting switch OFF (pushed in)
4
5. In Step 3, 4 and 5, 1 and 2 are readjusted, repeat 3, 4 and 5 again.
FM SSG
FEED SIGNAL MEASURE
STEP UBJECT ADJUST ADJUST FOR CONDITION
| aun | FROM | TO | OUTPUT )
1 | 88MHz 88MHz ANT REC OUTLor | L04 Max. output oSet Dial on 88MHz
Dial Calibration | ANT input 60dB terminal | R-ch
1kHz (100% MOD) | 3009 VTVM & Scope FM
FM
SSG
i
cocbyoabreabessboegt
2 | 108MHz 108MHz Same as | Same as Trimmer Same as eSet Dial on 108MHz
Dial Calibration | ANT input 60dB above above TC04 above
1kHz (100% MOD)
FM SSG is
104 = 106
Veaufoordianteno

FEED SIGNAL MEASURE
STEP ——— ADJUST ADJUST FOR CONDITION
3 | Confirm 88MHz | Same as Step 1 Same as | Same as Confirm olf not, repeat from
Dial Calibration above above 88MHz Dial Step 1
. Calibration
4 | Confirm 98MHz | 98MHz Same as | Same as Confirm
Dial Calibration | ANT input 60dB above above 98MHz Dial
1kHz (100% MOD) Calibration
FM SSG .
5 | Confirm Same as Step 2 Same as | Same as Confirm olf not, repeat from
108MHz above above 108MHz Dial Step 2
Dial Calibration Calibration
6 | 88MHz RF Adj. | 88MHz Same as | Same as LO1, LO2, L03 | Max. output eTune FM SSG (Max.
ANT
input
10dB
above
above
indication
of
Signal
1kHz (100% MOD) Meter)
FM SSG
7 | 108MHz RF Adj. | 108MHz Same as | Same as Trimmer Same as Same as above
ANT input 10dB above above TCO1, TCO2, | above
1kHz (100% MOD) TCO3
FM SSG
4-4. FM Signal Meter, Mono Distortion and Muting Adjustment
(See Fig. 4-9 on page 10)
Note: 1. Selector. ..........-ccc cece cececes FM AUTO
2. Master Volume ..............000. Minimum
FEED SIGNAL MEASURE
STE
BEC.
jo
————.
ADJUST
|
ADJUST
FOR
CONDITION
| sab | FROM [To | OUTPUT J
1 | Signal Meter | 98MHz ANT termi- | Signal Meter | VRO2 4.3 on meter oTune FM SSG (Max.
ANT
input
66dB
nal
indication
of
Signal
1kHz (100% MOD)}| 3000 Meter) : ;
FM SSG ; 5 oBefore adjustment, if
ens
meter
swings
out
or
not
enough,
preadjust
VRO2
until
the
reason-
able point
2 | Distortion Same as above Same as REC OUTL | TOS Min. distortion] oTune FM SSG (Nax.
above
or
R-ch
indication
of
signal
Dist. meter meter)
& Scope
3
|
Muting
Level]
98MHz
Same
as
REC
OUTL
|
VRO3
Audio
signal
oSet
FM
MUTING
sw
itch
ANT
input
24dB
above
or
R-ch
just
muted
to
OFF
(pushed
in)
1kHz (100% MOD) VTVM &
FM SSG Scope
Tielman iit i a Eg Tk ee OP ee ale FU ely Lig Mos

4-5. MPX Alignment (See Fig. 4-9 on page 10)
Note: 1. Selector ......ccccscccccccecceeens FM AUTO 4. Before adjustment, turn VRO1 CW (Max.) and VRO5 to
2. Master Volume..........0.cececeee Minimum center.
3. FM MUTING switch ............. OFF (pushed in)
STEREO SG
AUDIO OSC!
FEED SIGNAL MEASURE
STEP SUBJECT | FROM TO OUTPUT ADJUST ADJUST FOR CONDITION
1 19kHz 98MHz ANT REC OUT || LO08 Max. output oTune FM SSG (Max.
coil ANT input 60dB terminnal L-ch indication of signal _
FM SSG 3002 VTVM & meter) .
Pilot 19kHz Scope
(10% MOD)
L-ch 1kHz
(45% MOD)
R-ch (0% MOD)
Stereo SG
2 Separation Same as above Same as REC OUT VROS Min. output
above R-ch
VTVM &
Scope
3 Cofirm 98MHz Same as REC OUT Min. output olf less the 37dB adjust
Separation ANT input 60dB above L-ch VRO5
| FM SSG VIVM &
Pilot 19kHz Scope
(10% MOD)
L-ch (0% MOD)
R-ch 1kHz
(45% MOD)
Stereo SG
4 Indicator 98MHz Same as Stereo indi- | VRO1 Lighting Point |} oTune FM SSG (Max.
(Lighting ANT input 39dB above cator lamp indication of signal
level) FM SSG meter)
Pilot 19kHz
(10% MOD)
Stereo SG
4-6.
AM
IF,
Dial
Calibration,
RF
and
Signal
Meter
Alignment
(See
Figs.
4-5,
4-6,
4-7
and
4-9
on
page
10)
Note:
1.
SéleClOfviiicctciiewas
cceyetnue
ks
AM
2.
Master
Volume
............
eee
eee
Minimum
3.
Confirm
start
point
of
dial
pointer
before
alignment.
4. In
case
of
using
loop
antenna,
increase
output
of
AM
SSG
for
26dB than
bar
antenna’s
direct
input
as
it
attenuates
input
sensitivity
for
26dB
(See
Fig.
4-4).
3. After adjustment of signal meter, confirm the meter’s swing on FM. (If meter swings out or not enough, readjust VRO2.)
(See Page 8)
Fig. 4-4
Ci} BAR ANT
LOOP ANT
60cm