Sansui TU 777 Troubleshooting guide

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OPERATING II\TSTRUC TIOI\TS
& SERVICE IUANT]AL
SOLID-STAIE AM/FM STEREOPHONIC TUNER
SAI§ST]I TU_777
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SANSI{I 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 TIJ-777, incorporates the very latest in circuitry design,
including a new FET front end for increased FM sensitivity, high
stability;nd low distortion. It also features a dignified black
faced front panel, symbolic of all sansui high-grade sound equip'
ment. BeÍore 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 Íor future reference. Again, our sincere thanks for
purchasing the TU-777 and our best wishes for many years of
trouble-Íree stereo enjoYment.
G(lNTEilTS
OPERATION SECTION
Switches & Controls '...
Antenna Connection
Amplifier Connection
3,4
5,6
6
7
General Maintenance .........
Spe cifi cationsf Characteristics
SERVICE SECTION
General Troubleshooting Chart " L7, L2
DisassemblyProcedure.... ""' 13
DialMechanism "' 13
Custom Mounting
Test Points Chart
Alignment Procedure
FM..
FM.MULTIPLEX
AM..
Printed-Circuit Sheets & Parts List . .... 19, 20,2L,22,23
BlockDiagram "' 24
Other Parts & Theiv Pusition on Chassis . " ' 25,26
7,8
9, 10
t4
15
16
L7
18

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.. ti,::::,i
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SIryITCHES & CONTROLS
Power Switch
The TU-777 goes on when
lever is set to ON Position. POWER switch Muting Switch
Eliminates interstation tuning noise when select
ing F\{ stations. It should be used sparingly
particularly if the tuner is located in a weak signa
area. When you $'ant to receive a t'eak station
this switch should be kept off.
FM Stereo Indicator
Iiluminates whenever the tuning dial passes
station broadcasting an FN{'N4PX program. Doe
not light up for regular F\{ monaural broadcasts
Power Indicator
Lights up whenever the tuner is receiving cur
rent. Remains lit as long as the Pos'er Switch ;
On.
-3-

* Dial Scales
For more convenient tuning, theTU-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.
)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.
Tuning Indicator
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.
MP)( 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-
times impair the separation of stereo sounds.
High frequency sounds are not affected when this
switch is on.
F
FM Antenna Local-Distant switcl,
GND grounding terminal
Antenna terminal
AM Ferrite bar antenna
AC.Outlet
Power fuse
O utput
Output level adjustment Control
FM Stereo separation adjustment Control
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ANTENNA CONNECTION
AMPLITIER CONNECTION (

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ANTENNA CONNECTION
t
The quality of reception that can be expected from
theTU-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 usuaily adequate for strong AM recep-
tion. To use, puli 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 Íeeder wire to the antenna
terminals marked FM-AI and FM-Az on the rear
panel, then fully extend the wire to a T shape and
fix it to a wall or ceiling where it aliows 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
clesigne<i exclusively for FM reception should then
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FM antennas of the 300 ohm balanced type and 75
ohm unbalanced type can be used with theTU'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.1 and Az 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 trig. 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 isto 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-
6er 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:
1. 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 move§ 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.
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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.
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.
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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
'fheTU-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 po\À/er capacity.
Power Fuse
If the tuner fails to operate when the power is
switched on, its power fu§e may be blown. To
check, turn the fuse holder at the rear of the tuner
to the left. If it 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 shouid be avoid-
ed. If the new fuse blows when the power is
switched on again, contact your nearest Sansui
dealer or our Service Section.
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Level Adjustment Control
This control, labeled LEVEL ADJ. on the rear
panei of the tuner, allows theTU-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.
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 SiN ratio to be obtained. FM AM
À-30OO-A2 A

SPECIFIGATIONS
GHARACTERISÏICS
FM SENSTTIV]TY OHF) & IMAGE RATIO FM SECTION
FREQUENCY RANGE: From 88 io 108 MHz
SENSITIVITY:
Antenno input 300O bolonced 1.4PV
(S/N 20 dB, quietins)
l.8pV (lHF)
Antenno input 75O unbolonced 0'7pV
(S/N 20 dB, quietins)
l.opv (lHF)
IMAGE REJECTION: Better thon 80 dB (lHF)
SELECTIVITY: Better thon 50 dB (lHF)
SIGNAL TO NOISE RATIO: Better thon ó5 dB (ó0 dB
input, 100% mod.)
HARMONIC DISTORTION: Le§s rhon 0'81 (ó0 dB
input, 100% mod.)
SPURIOUS RESPONSE REJECTION:
Better thon 90 dB
lF REJECTION: Better thon 95 dB
SPURIOUS RADIATION: Less thon 34 dB
CAPTURE RATIO: Less thon 2'5 dB (lHF)
FM STEREO SEPARATION: 35 dB (óOdB input' 100%
mod.)
AM SECTION
FREQUENCY RANGE: From 535 to l,ó05kHz
SENSITIVITYi lsttV (ot 1,000 kHz, S/N 20 dB)
SELECTIVITY: Better thon 20dB (ot 1,000 kHz,
ó0 dB input)
DTSGRIMINATOR
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CARRTER FREOUENCY (MHz) -.-
F8ÉOUEhrí orFFERElrcÉ{X}u -
S/N & DISTORTION
i FREOUEN'Y 98i'H'
MODULAÍCN IOO% 4MH?