Sansui TU 777 Troubleshooting guide

SANS-00184
OPERATING INSTRUCTIONS
& SERVICE MANUAL
SOLID-STATE AM/FM STEREOPHONIC TUNER
SANSUI TU.777
SANSUI ELECTRIC COMPANY LIMITED

Thank you for purchasing the Sansui TU-777. In doing so, you
have made a wise choice, one that promises you many delightful
years of rich stereo enjoyment.
Model TU-777, incorporates the very latest in circuitry design,
including a new FET front end for increased FM sensitivity, high
stability and low distortion. It also features a dignified black
faced front panel, symbolic of all Sansui high-grade sound equip-
ment. Before leaving the Sansui factory, this model was tested,
inspected and certified to be in perfect working order.
To keep it that way, it is imperative that you read the Opera-
tion section of this manual thoroughly before attempting to in-
stall and use the tuner. Since this manual also contains other
helpful information on checking and servicing the tuner, and in-
stalling it in a custom-made cabinet, you will undoubtably want
to retain it for future reference. Again, our sincere thanks for
purchasing the TU-777 and our best wishes for many years of
trouble-free stereo enjoyment.
CONTENTS
OPERATION SECTION
Switches & Controls: -i2vivissaticedi tis Mon tear ete sakes’ 3, 4
Anterina Contection: cecchatevigeced estat hots sean adeee ned 5, 6
Amplifier Connection: ¢02) hie os sepaccdsen esa bid tera terior dyaees 6
OpetatiOnt o5..50 nent tee tree es ea tae eee est 7
General Maintenance se: i5e5-so055 se. Saeenioueieat cupedacs 7,8
Specifications/Characteristics .......... 0... :ce ee eeecee eee eeeene 9, 10
SERVICE SECTION
General Troubleshooting Chart ................. 2. cee ee senna 11, 12
Disassembly Procedure.................cccccccceeeseeeeeeseeseeees 13
Dial. Mechamisint sc.cecedetietet even Stone es eee eo Sea vs 13
Custom Mounting ............. ccc cece cece cee ce cece cane sec eeenees 14
‘Lest Poitits Charticceois test artasse eta reaeeweedechieienditwesnnets 15
Alignment Procedure
PM ores ei eesen hein sere eid. bees ied te basen eepetendlnawdeaua ded ee hes 16
PMEMULTIPLER: tacicimersuccioaigah cede viestortastands alee 17
PM i aria ness te Gh adele en np aa ene caMencgsaet aa aeaN 18
Printed-Circuit Sheets & Parts List ............ 19, 20, 21, 22, 23
Biéek Diagram \cdisvisscvss cath detec dueeuc aden caSddsaas bathe 24
Other Parts & Theiv Pusition on Chassis .................. 25, 26

SWITCHES & CONTROLS
FM STEREO
POWER MUTING — NOIS!
Power Switch
The TU-777 goes on when POWER switch
lever is set to ON position,
Muting Switch
Eliminates interstation tuning noise when select-
ing FM stations. It should be used sparingly,
particularly if the tuner is located in a weak signal
area. When you want to receive a weak station,
this switch should be kept off.
FM Stereo Indicator
Iluminates
whenever
the
tuning
dial
passes
a
station
broadcasting
an
FM-MPX
program.
Does
not
light
up
for
regular
FM
monaural
broateasts.
Power Indicator
Lights
up
whenever
the
tuner
is
receiving
cur-
rent.
Remains
lit
as
long
as
the
Power
Switch
is
On.

LS
STS
SS
SS
— ~~ Dial Scales FM Antenna Local-Distant switct,
For more convenient tuning, the TU-777 features
a rounded dial window. The outside dial corre-
sponds to the FM band, the inside dial to the AM
band. Both bands share a single dial controlled
by the Tuning Knob. AM Ferrite bar antenna
Antenna terminal
—— Tuning Knob
Use to select both AM and FM stations. Be sure
to watch the Tuning Indicator when using this
control for pinpoint station accuracy.
—- Function Selector
Allows the following selections to be made:
AM: for ordinary AM band broadcasts
FM MONO: for FM band monaural broadcasts
FM AUTO: for both monaural and stereophonic
FM band broadcasts. Tuner switches automatic-
ally to either signal depending on what is being
broadcast.
FM STEREO: for FM stereophonic broadcasts
exclusively. Use if stereo signal is too weak and
automatic switching is unstable in the FM AUTO
position.
AC-Outlet
Tuning
Indicator
Power
fuse
Aids
in
pinpointing
stations
with
the
Tuning
Knob.
Stations
are
accurately
tuned
when
the
needle
in
this
window
swings
as
far
to
the
right
as
possible,
but
not
necessarily
to
“5”.
This
move-
ment
may
vary
from
station
to
station.
Output
MPX Noise Canceler
Use to depress disturbing noise when listening to
an FM stereo broadcast, but only if disturbing
noise occurs. In weak signal areas it may some- Output level adjustment Control
times impair the separation of stereo sounds.
High frequency sounds are not affected when this FM Stereo separation adjustment Control
Switch is on.
GND grounding terminal

ANTENNA CONNECTION
AMPLIFIER CONNECTION
UNSWITCHED:
MAX 150V)
SEPAILATION MAX 1hOVA
a
RIGHT CHANNEL LEFT CHANNEL
MAMET,
x) e986 © €@
q°q9@q@ opp RP
CONTROL AMPLIFIER
XR
OX o,9,
RNAP
RRR
DOO i
RRS \
ie
Kx eS Il
BEGET
erararerertentieest
DOXKRK YN
RRO REIS
ye RON
AK

ANTENNA CONNECTION
The quality of reception that can be expected from
the TU-777 is largely dependent on the correct posi-
tioning and use of antennas. The following proce-
dures are recommended for noise-free reception.
Built-in AM Ferrite Bar Antenna
This sensitive antenna, located on the rear panel of
the tuner, is usually adequate for strong AM recep-
tion. To use, pull it down and away from the back
of the tuner until it comes to a stop halfway between
the top and the bottom of the tuner.
Outdoor AM Antenna
In ferroconcrete buildings or in areas remote from
the broadcasting station, the built-in ferrite bar
antenna may be inadequate for strong AM recep-
tion. An outdoor antenna then becomes necessary.
This can be accomplished by connecting the PVC
wire accompanying the tuner to the antenna termi-
nal marked AM-A on the back panel. Run this wire
to an antenna that has been installed outdoors and
away from the building. At the same time, the unit
should be grounded. Position the outdoor antenna
where reception is strongest while actually receiv-
ing a broadcast. And, for reasons of safety, be sure
to attach a lightning arrester to the outdoor an-
tenna.
FM Antenna
Where FM broadcasting stations are near and FM
signals are strong, satisfactory FM reception can be
obtained by using the feeder wire accompanying
the tuner. Connect the feeder wire to the antenna
terminals marked FM-A, and FM-A, on the rear
panel, then fully extend the wire to a T shape and
fix it to a wall or ceiling where it allows the strong-
est reception.
If the TU-777 is used in a thick-walled building or
in an area remote from FM broadcasting stations,
the indoor feeder wire antenna may be inadequate
for strong signal reception. An outdoor antenna
designed exclusively for FM reception should then
be installed.
FM antennas of the 300 ohm balanced type and 75
ohm unbalanced type can be used with the TU-777.
Connect either antenna to the matching antenna
terminals on the rear of the tuner. The 300 ohm
feeder wire should be connected to the FM antenna
terminals A; and A, as in Fig. 1.
If a 75 ohm coaxial cable is used, connect the con-
ductor to the FM antenna terminal A, and the
shielding wire to the terminal G as in Fig. 4.
NOTE: FM sensitivity cannot be raised simply by
lengthening the antenna. Adjust the antenna’s
height and direction while actually listening to a
broadcast for the best reception.
AMPLIFIER CONNECTION
The TU-777 has been provided with two cords for
quick and convenient connection to an amplifier.
One is marked L and corresponds to the left stereo
channel, the other is marked R and corresponds to
the right. If the TU-777 is to be used with Sansui’s
matching AU-777 amplifier or any other Sansui
amplifier, insert the pin plugs of each cord into the
amplifier inputs labeled TUNER or AUX respec-
tively. Be sure in either case, that cord L is insert-
ed into the left input and R is inserted into the right
input. If the TU-777 is to be used with an ampli-
fier other than Sansui, the same procedures general-
ly hold true, but it is best to check the manufac-
turer’s instructions to be sure.

OPERATION
GENERAL MAINTENANCE
RADIO PROGRAMS
To receive AM broadcasts:
1. Turn the Function Selector to AM
2. Select the desired AM station on the AM dial
with the Tuning Knob. It is properly tuned when
the needle in the Tuning Indicator woves as far to
the right as possible.
To receive FM broadcasts:
l. Turn the Function Selector to FM MONO for
regular monaural broadcasts, to FM AUTO for both
monaural and stereo broadcasts, and to FM ST-
EREO for only stereo broadcasts.
NOTE: If stereo reception is unstable with the
Function Selector in the FM AUTO position, turn
to FM STEREO.
If too much disturbing noise accompanies a stereo
broadcast in either FM STEREO or FM AUTO
positions, first switch the NOISE CANCELER on,
and if the noise is still too disturbing, turn the Func-
tion Selector to FM MONO to hear the same broad-
cast monaurally.
2, Select the desired FM station on the FM dial
with the Tuning Knob. It is properly tuned when
the needle in the Tuning Indicator moves as far to
the right as possible. The FM Stereo Indicator il-
luminates automatically whenever an FM stereo
broadcast is being received.
3, When too much interstation noise is during tun-
ing, turn the Muting Switch to its On position.
4, It is best to adjust the output level of the tuner
to match that of other sound equipment being used
with the amplifier. This can be done by turning the
LEVEL ADJ. control on the rear of the panel to
either a higher or lower level.
GENERAL
MAINTENANCE
FM Stereo Separation
If
the
channel
separation
during
FM-MPX
stereo
reception
is
inadequate
or
excessive,
turn
the
screw
marked
MPX
SEPARATION
on
the
rear
of
the
tuner
for
natural
proportions.
Never
attempt
to
adjust
it
without
reason
however,
as
it
has
been
properly
adjusted
and
tested
prior
to
leaving
our
factory.
SEPARATION
Local-Distant
Antenna
Switch
This
switch
helps
to
adjust
the
tuner
to
the
strength
of
FM
signals
in
whatever
area
it
is
being
used.
Set
it
to
DIST
if
you
live
in
an
area
where
FM
signals
are
weak.
If
you
live
near
broadcasting
sta-
tions
where
there
is
danger
of
interference
between
stations,
set
the
switch
to
LOC.

Where to Place
Since transistors are extremely susceptible to heat,
the TU-777 has been designed to diffuse heat
through the top and rear of its case. Therefore,
special consideration should be given to where it
will be used before installing the tuner. It should
not be operated in a place where it is exposed
directly to the sun, near radiators or other heat-
generating sources, and it should never be mounted
in an air-tight cabinet. Finally nothing should be
placed on top of it.
AC Outlet
The TU-777 has ben provided with a 150VA power
outlet on its rear panel. It can be used an AC power
source for other components such as a turntable,
but care should be taken not to use it for any com-
ponent that exceeds its 150VA power capacity.
UNSWITCHED
FUSE MAX .ASOVA
replace with Pe)
some type 1A fuse
oN
Power Fuse
If the tuner fails to operate when the power is
switched on, its power fuse may be blown. To
check, turn the fuse holder at the rear of the tuner
to the left. [fit is blown, disconnect the tuner from
its power source and replace the fuse with an
identical 1A fuse, after finding and eliminating the
source of trouble that caused the fuse to blow.
Using wire or a fuse of a different capacity as a
stop-gap measure is dangerous and should be avoid-
ed. If the new fuse blows when the power is
switched on again, contact your nearest Sansui
dealer or our Service Section.
Level Adjustment Control
This control, labeled LEVEL ADJ. on the rear
panel of the tuner, allows the TU-777’s output level
to match that of turntable, speakers and other com-
ponents connected to an amplifier. Turned clock-
wise, it increases the output level of AM and FM
broadcasts; turned counter-clockwise, it decreases
the output level of both.
LEVEL ADJ.
Grounding
Connect one end of vinyl or enameled wire to the
terminal screw marked GND at the rear of the
tuner, attach a copper plate to the other end, and
bury it underground. Whenever an outdoor AM
antenna is used, grounding becomes necessary. In
all cases, grounding is desireable since it allows a
better S/N ratio to be obtained.
tte 7 7 J 7 V4
COPPER PLATE COPPER PLATE
BURIED UNDERGROUND. BURIED UNDERGROUND.

SPECIFICATIONS
CHARACTERISTICS
FM SENSITIVITY (1HF) & IMAGE RATIO FM SECTION
10 1 FREQUENCY RANGE: From 88 to 108 MHz
IMAGE RATIO
oo —} = SENSITIVITY:
PA | Antenna input 3002 balanced 1.44V
8 all | (S/N 20 dB, quieting)
- 1.82V (IHF)
zo) Antenna input 75Q unbalanced 0.74V j
2 2
z (S/N 20 dB, quieting)
SENSITIVITY 1.02V (IHF) :
IMAGE REJECTION: Better than 80 dB (IHF)
88 92 96 100 104 108 SELECTIVITY: Better than 50 dB (IHF)
CARRIER FREQUENCY (MHz)—~
SIGNAL TO NOISE RATIO: Better than 65 dB (60 dB
SIGNAL TO NOISE RATIO, OUTPUT
LEVEL VS ANTENNA INPUT input, 100% mod.)
ey ee Ee eee HARMONIC DISTORTION: Less than 0.8% (60 dB
: ne input, 100% mod.)
vf SPURIOUS RESPONSE REJECTION:
; Better than 90 dB
é—i5- DW SS HO IF REJECTION: Better than 95 dB
INA INPI *
—— SPURIOUS RADIATION: Less than 34 dB
Ree iach bales CAPTURE RATIO: Less than 2.5 dB (HF)
dle FM STEREO SEPARATION: 35 dB (60dB input, 100% “fg
| mod.)
rg AM SECTION
Fa FREQUENCY RANGE: From 535 to 1,605 kHz
| | 3 SENSITIVITY: 15zV (at 1,000 kHz, S/N 20 dB)
Lt SELECTIVITY: Better than 20dB (at 1,000 kHz,
| 8 b -ARRIER 60 dB input)
2. EQUENCY
_ oe MHz
Ba) -400 -200 0 +200 +400 +600
FREQUENCY DIFFERENCE (KHz) —=
S/N & DISTORTION DISCRIMINATOR
— I r
0.3)
8
° Nn
WUTPUT VOLTAGE {VV}
2
&
;
FREQUENCY --- 98MHz
1 MODULATION:-100% 400Hz
3
RESPONSE (dB) -
; t
200 460 600)
}O.7MHz. eREQUENCY
DIFFERENCE - -
(KHz) H
&
+ { !
= oN
DISTORTION (%]—=
TorsToRT 1ON
oc 20 80° 100 120 i ct
40 60
ANTENNA INPUT {d8Aiv]-——
ee Nea ee a RT TE ECE A PR TS a RP NE ASL CE Ee Sa, ee Ad mee ee ORR ee ee ee Te eT