ZANUSSI

TIP Model / Chassis

SERVICE MANUAL
ZANUSSI 22ZT907
ZANUSSI BS-400.2 CHASSIS
 ZANUSSI

SERVICE DEPARTMENT

SETCO/ACF

Model
22 ZT 907

Zanussi Elettrorrica S.p.A. reserve all legal rights

to the exclusive ownership of this document and . * .-
:
C. 430-2-1982 (UK) (54)
hereby prohibit reproduciion or disclosure of the
same without their prior permission.
 CONTENTS

- GENERAL FEATURES ....................... 1

- CONTROLS ON THE RECEIVER ............... 2
- ACCESS TO INTERNAL COMPONENTS .......... 4
- VIEW OF CHASSIS AND OF DISCONNECTED
PLUG-IN TYPE P.C.BOARDS ............... 5
- REFERENCES FOR MAIN ADJUSTMENTS ........ 6
- TRANSISTORS ............................ 8
- INTEGRATED CIRCUITS .................... 10
- MAIN COMPONENTS ........................ 12
- ADJUSTMENT PROCEDURE ................... 16
- TELETEXT TRANSMITTER ................... 24
- PROCUCT SAFETY NOTICE ................. 33
 ‘. _: .:
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GENERAL FEATURES
:.

CHASSIS : BS 400.2
PICTURE TUBE : 22" PIL s 4 - A 56-701 X
POWER SUPPLY .. 240V AC + 10% 50 Hz
POWER ABSORBED : Medium/maximum 110/140 W
EHT : 24.5 kV
MAX. BEAM CURRENT .. 1.1 InA
ANTENNA INPUT : 75 Ohm
TUNER .. Varicap integrated type
TUNING SYSTEM .. Electronic (voltage synthesis type)
PRESELECTION .. 16 TV programmes and VCR on programme
16
AFC : Insertable through pushbutton
REMOTE CONTROL .. IR type. Max. range approx. 8 m
REMOTE CONTROL TRANSMITTER In stand-by < 20 /uA
..“..,.,
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ABSORPTION { In operation < 9 mA
._‘.,._.
CLOCK : Electronic programmable type with
digital hours and minutes indication
AUXILIARY OUTPUT JACKS : Headphones jack 8 Ohm DIN 45327
Tape recorder 47 kOhm DIN 41524
External loudspeaker jack 2.7 Ohm
DIN 41529
LOUDSPEAKER : Lateral woofer and frontal tweeter
AUDIO OUTPUT .. 15 W
STANDARD .. CCIR - I PAL
DEGAUSSING : Automatic
DIMENSIONS : 55x55~42 cm
WEIGHT .. 29 kg

.. *-
. *. .-

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CONTROLS ON THE TV RECEIVER

Front controls

1. Electronic clock
.2. Control panel *cover
3. Switch-ON & programme
sequential channel change
control
4. Digital programme dispaly
5. Stand-by switch
6. Output jacks recess cover
7. Remove control receiver
8. Clock brightness control
9. Clock reset - hours H
10. Clock reset - minutes M
11. Volume
12. Tone control - treble
13. Tone control - bass
14. Brightness
15. Colour control
16. Contrast
17. Clock programmer
18. UHF band indicator light
19. AFC indicator light
20. AFC pushbutton
21. Station scanning control - S
22. Fine tuning regulation
23. Tuning sequence lights
24. Recording jack
25. Output jacks foldback release
26. Headphones jack

-2-
Rear sockets

27. Auxiliary speaker jack

28. Aerial socket
29. Clock battery recess

-3-
 _‘.
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ACCESS TO INTERNAL COMPONENTS

To remove back panel:

1. Insert a blade screwdriver into "A";

2. Push down retaining lug “B” ;

3. Release bottom part and remove panel.

i

-a_
 VIEW OF CHASSIS AND OF DISCONNECTD PLUG-IN TYPE P.C.BOARDS
,. -:
,..::,
.:,._ .:’

BS 400

BS 417

BS 397 BS 395
BS 398

BS 399

BS 396

BS 4 .a

LEGEND

BS 400.2 Chassis
BS 417 Power supply p.c.b,
BS 395 Line output p.c.b.
BS 396 Synchro. separator and pincushion correction p.c.b.
BS 418 CRT discharger p.c.b.
BS 399 Video p.c.b.
BS 398 IF unit p.c.b.
BS 397 Vertical deflection p.c.b. A *. .-

-5-
 REFERENCES FOR MAIN ADJUSTMENTS

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s 417
P 303

301

P 401
402
P 403

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LEGEND

Pl AGC adjustment potentiometer

P 351 Vertical linearity adjustment potentiometer .
P 352 Vertical frequency adjustment potentiometer
P 353 Vertical amplitude adjustment potentiometer
P 354 Raster adjustment potentiometer
P 551 Potentiometer for (grid-2) adjustment of picture tube
BS 418 CRT discharger p.c.b.
SW 553 Switch for blue electron gun
SW 552 Switch for green electron gun
P 552 Focus adjustment potentiometer
SW 551 Switch for red electron gun
BS 417 Power supply p.c.b.
.P 303 Potentiometer for adjustment of +12.6v DC *. .-
P 301 Potentiometer for adjustment of +15OV DC
‘.
P 401 Oscillator frequency adjustment potentiometer
.;
,;.:. “i ‘;; P 402 Pincushion adjustment potentiometer
._
”
,’ P 403 Horizontal amplitude adjustment potentiometer

-6-
BS 395 Line output p.c.b.
BS 396 Synchro. separator and pincushion correction p.c.b.
BS 397 Vertical deflection p.c.b.
BS 398 IF unit p.c.b.
BS 399 Video p.c.b.
P 108 Peak-to-peak adjustment potentiometer (blue)
P 109 Black level adjustment potentiometer (blue)
P 106 Peak-to-peak adjustment potentiometer (green)
P 107 Black level adjustment potentiometer (green)
P 104 Peak-to-peak adjustment potentiometer (red)
P 105 Black level adjustment potentiometer (red)
P 103 Potentiometer for adjustment of direct signal level
L 102 Burst phase adjustment coil
C 123 Capacitive trimmer for oscilloscope adjustment
 TRANSISTORS

Transistors mounted on chassis and p.c.boards

Transistors Type Electronic functions

Tl BF 479 S UHF amplifier

T3 BF 680 Oscillator/convertor UHF
T4 BF 506 UHF amplifier
T6 BF 199 IF amplifier
T7 BC 548 B Audio amplifier
T8 BC 548 B Impedance matcher
T 101 BC 548 B Automatic control of p.p. luminance
signal
T 1 0 2 BC 548 B Brightness control fixed level setting
for adjustment of the output video
amplifiers
‘, ,;.
T 103 BC 548 B T 101 driver
.‘,
:_ ~
T 104 BC 548 B Suppressor of unwanted reflections on
the burst signal delay line LR 102 of
the chrominance channel
T 105 BF 393 Active load
T 106 BF 758 Video output
T 107 BF 393 Active load
T 108 BF 758 Video output
T 109 BF 393 Active load
T 110 BF 758 Video output
T 261 TIL 78 Optoelectric coupler
T 262 BC 548 B Amplifier
T 263 BC 548 Switching transistor
T 264 BC 320 B Switching transistor
T 265 BC 548 B Driver for optoelectric coupler
T 266 BC 320 B Driver for optoelectric coupler
T 301 BC 557 B Amplifier
T 302 BU 326 A Oscillator
T 303 BC 548 B Switch for remote control
.,
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::.__ :.: :-
T 351 BD 135 Switching transistor
._ T 352 BD 243 A Vertical parabola amplifier
T 353 BD 244 A Vertical parabola amplifier
T 354 BC 548 B Multivibrator for formation of vertical
T 355 BC 548 B blanking pulse
T 402 BC 548 C Parabola signal amplifier
T 403 BC 558 B Parabola signal amplifier
T 404 BD 679 Amplifier
T 451 BF 758 Amplifier switch
T 452 BU 208 A Line output

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 ,. ._
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TRANSISTORS
.
Transistors mounted on remote control and tuning unit

Transistors Type Electronic functions

T 702 BC 547 B Driver for DL 651

T 704 BC 547 B AFC enabler

T 705 BC 547 B Clipper

T 801 BC 413 C AGC

T 802 BC 413 C Amplifier

T 803 BC 413 C Amplifier

T 804 BC 253 C Amplifier

T 805 BC 170 C Square-wave shaping

T 806 BC 320 B Driver for display's lit spot

T 807 BC 320 B Driver for display's lit spot

T 808 BC 320 B Driver for display's lit spot

T 809 BC 548 B Colour adjustment

T 8i0 BC 548 B Volume adjustment

T 811 BC 320 B Muting

T 812 BC 548 B Muting

.:- : 1 _;
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T 813 BC 548 Output impedance matcher

T 814 BC 548 Output impedance matcher

T 815 BC 548 Output impedance matcher

-Y-
INTEGRATED CIRCUITS

ICs mounted on chassis and p.c.boards

:cs Type Electronic functions

CI 1 TDA 2541 IF amplifier. Carrier generator and

synchronous detector. Video preamplifier.
White peaks inverter stage - AGC - AFC.

CI 2 TBA 120 U Amplifier/limiter. Coincidence detector.

Reference frequency generator for
detection. Low frequency audio signal
output with insertion of volume
adjustment. Low frequency audio signal
output without volume adjustment.

CI 101 TDA 2151 Luminance/chrominance signal processing.

Brightness, contrast and colour controls.
Beam current limiter.

CI 102 TDA 2140 Colour subcarrier regeneration. PAL

switching. Identifier. Killer. AFC and
automatic phase control. ACC. Burst.

CI 103 TDA 2161 R-Y/B-Y demodulators. G-Y matrix.

Luminance matrix.

CI 201 TDA 4290 Continuous path control adjustment of

treble, bass and volume.

CI 202 TDA 2030 Audio amplifier.

CI 261 TDD 1618 l8V stabilizer.

CI 262 MC 14013 Switch-ON reset. TV start signal 24h

clamp pulse.

CI 301 L 200 v 12.6V stabilizer.

CI 351 TDA 1170 S Square-wave signal generation. Conversion

of the square-wave signal into a
saw-tooth signal. Saw-tooth signal
amplification. Voltage stabilization
of all internal circuits.

CI 401 TDA 2593 Synchro. separator. Phase comparator.

15625 Hz oscillator. Phase shift.
Generator of the driving pulse for the
line output amplifier. Sand-castle
generator.
*. .-

-lO-
INTEGRATED CIRCUITS

ICs mounted on remote control and tuning unit

ICS Type Electronic functions

CI 651 MC 14493 P It drives DI 651 display

CI 701 MC 14426 Memory for 8 programmes

CI 702 MC 14426 Memory for 8 prograinmes

CI 703 MC 14429 Control unit

CI 704 UAA 1008 Band decoder. Coincidence detector.

Operational amplifier. AFC processing.

CI 705 4071 BE Two-input OR

CI 706 4049 D Inverting buffer

CI 707 4013 Double flip-flop

CI 708 SN 16889 P Tuning indicator

CI 801 SAA 1051 It processes information coming from

remote control.

CI go1 SAA 1050 Remote control transmitter

. *. .-

-ll-
 MAIN COMPONENTS

BS 400.2 Chassis - It supports the p.c.boards and

it supplies voltages for EHT,
focusing system and CRT heaters.

BS 398 Tuner - IF video/audio - Conversion of the RF signal into

p.c.b. an IF signal (video carrier:
39.5 MHz;, audio carrier:
33.5 MHZ).
Detection of the IF signal into
low frequency video and audio
signals.

BS 399 Luminance-chrominance and - This p.c.b. processes the

video amplifier p.c.b. complete composite video signal
coming from the IF p.c.b. and
supplies the R-G-B signals to
the picture tube.

BS 401 Audio p.c.b. - This p.c.b. receives the audio

signal (not adjusted in volume)
coming from p.c.b. BS 398, it
adjusts it in amplitude and
tone, it amplifies it and sends
it to drive the two receiver's
loudspeakers (tweeter and
woofer).
Through jack PR 201 it is
possible to connect externally
an auxiliary 2.7 Ohm loudspeaker
with or without the exclusion
of the internal loudspeakers.
Furthermore, the p.c.b.
transferes the audio signal
(not adjusted in volume) to
taperecorder and headphone
jacks.

No adjustments needed.

BS 470 Mains filter p.c.b. - The p.c.b. includes circuits

relevant to: mains filter,
degaussing, remote control
SUPPlY, start remote control.
No adjustments needed.

BS 380 Power supply p.c.b. - It includes circuits for

clock supply and for switch-ON ~
. * .-._
programming.

No adjustments needed.

-12-
BS 417 Power supply p.c.b. - It converts the mains voltage in
DC voltage available at five
outputs with values of: +2OOV;
+15OV; +27V (two outputs);
+12.6v. These voltages are
stabilized and separated from
the mains.

BS 397 Vertical deflection p.c.b. - This p.c.b. generates a sawtooth

voltage at frame frequency which
is used for driving the vertical
deflection yoke. It supplies a
similar voltage to the
l'pincushionll section of the
synchro. separator p.c.b. to
obtain the E/W pincushion
correction.
It supplies a frame frequency
pulse which is used for the
luminance, chrominance and video
amplifier p.c.b. blankings. It
receives the vertical synchro.
from the synchro. separator
p.c.b. and receives from the
chassis a voltage proportional
to the beam current.

BS 396 Synchro. separator and - The p.c.b. processes the video

pincushion correction signal. Said process consists in
p.c.b. separating the horizontal
signals from the video composite
signal. The "pincushion
correctionl' section receives a
sawtooth shaped signal and
converts it into a parabolic
shape for E/W correction.

BS 395 Horizontal deflection - This p.c.b. amplifies the pulse

p.c.b. sequence at line frequency and
drives a circuit operating as
an ON-OFF switch for supplying
the deflection current to the
horizontal yoke. It also
receives the parabolic signal
which acts on the diodes
modulator for E/W correction.

No adjustments needed.

BS 418 CRT p.c.b. It includes protection and

matching circuits for the three
signals (red, green and blue) ;~ .-
with relevant voltage * ._
dischargers. In series to each
signal circuit a switch is
provided for black level
adjustment.
 The p.c.b. includes a cut-OFF
circuit which stops the CRT
luminous emission during the
blanking phase.

BS 385 Auxiliary outputs jacks - This p.c.b. receives the audio

p.c.b. signal (amplified and volume
adjusted) and supplies it to an
auxiliary jack for private
headphone listening.
A non-volume-regulated signal is
also supplied to a socket for
taperecording.
The headphones output complies
to Standard DIN-45327 and has an
impedance of 8 Ohm. The
taperecorder output complies to
Standard DIN-41524 and has an
impedance of 47 k0hm.

No adjustments needed.

BS 387 IR preamplifier p.c.b. - It converts IR pulses coming

from the transmitter into
electrical pulses. These are
amplified and appropriatly
clipped.

No adjustments needed.

BS 389 Remote control receiver - It receives the command signals

p.c.b. coming from the sequential
programme pushbutton, it
processes them and converts them
into control signals. Tone and
contrast controls also pass
through this p.c.b., said
control signals being fed from
the control unit and being
forwarded to the chassis.

No adjustments needed.

BS 405 Front control unit p.c.b. - This p.c.b. includes

potentiometers for volume,
brightness, saturation,
contrast, treble and bass.
This p.c.b. also includes
pushbuttons relevant to
sequential control, AFC,
automatic search, forward
tuning, bachward tuning, band
and tuning indicating LEDs.

-14-
 The display indicates the
programme selected. Furthermore,
this p.c.b. includes all
pushbuttons for clock
adjustment.

No adjustments needed.

BS 388 Tuning unit p.c.b. - Automatic searching of a TV

station through a start command.
Manual searching of a TV station
through two commands (increment
and decrement).
Inclusion-exclusion of the AFC
circuit with LED display.
Band indication displayed on
three LEDs. Tuning level
indication with five LEDs.
Memorization of 16 selected
programmes manually or with
remote control.

No adjustments needed.

BS 414 a/b Remote control p.c.b. - This p.c.b. enables remote

control of the following
functions: selection of 16
programmes; "+" or "-" volume
adjustment; brightness and
saturation adjustment; audio
silencing; TV receiver ON/OFF
switching.

No adjustments needed.

*. .-

-?5-
 ADJUSTMENT PROCEDURE

PCB BS 398

Denomination : Tuner IF video/IF audio

Adjustment procedure for IF section

Instruments used: - 0 to 30V adjustable power supply.

- 0 to 12V adjustable power supply.

- 12.6~ - 200 mA power supply.

- Sweep generator, >lO MHz and

markers at: 31.5, 33.5, 35.1.
36.5, 39.5, 41.5 and 37.1125 MHz
for adjustment of output filter.

- Dual trace oscilloscope - 10 MHz

pass-band.

IF signal (video carrier

39.5 MHz and audio carrier
33.5 MHz) with 100% standard
video modulation, bar modulating
signal, 20% white level - 76%
black level.
Audio carrier modulated at 1 kHz
with + 50 kHz of deviation at
50 /us of preemphasis.
- Voltmeter (15V setting).

Note: See legend of test points (TP) at the end of adjustment procedure.

Preliminary operations:

- Supply the p.c.b. with 12.6V at terminal A 9.

- Adjust the varicap voltage to 26V (terminal B 1).

- Position the wipers of P 1 and P 2 towards earth so as to have

connected the maximum resistance.

-16-
Connect the sweep generator with a probe (see figure below) to TP 1:

1OnF

Connect a high impedance detector probe on collector of T6. See figure

below:

6PF SFD104 390 r&

-----
-- -_ *
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1

ADJUSTMENTS

Adjustment of RF unit output filter

l- Adjust L40 and L49 for a curve as that shown in figure,

corresponding to best coupling and balancing:

37.125Mt-k

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30MHz

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*. .-

2 - Disconnect the probe from collector of T6.

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Adjustment of reference circuit
.‘..

1 - Connect the oscilloscope's probe to video output (A 6).

2- Connect the IF signal (complete of modulated audio) at 10 mV level

on TP 1.

3- Adjust L44 for minimum amplitude of demodulated signal,

corresponding to the best response transients or to 2 T pulse.

Adjust the 6 MHz trap and the audio input filter

l- Adjust L46 and L48 for lowest output of 6 MHz signal present in
video,signal.

Adjustment of audio quadrature coil

.:; __::
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..:::::$_:. l- Move the oscilloscope's probe to pin 8 TBA 120 U (LF audio output).

2- Give a max. 12V bias to the volume control terminal A 2.

3- Connect a 10 kOhm resistance between pin 13 of TBA 120 U and the

+12V and read the DC voltage.

4- Disconnect the 10 kOhm resistance.

5- Adjust L47 until the DC voltage corresponds again to value measured

previously.

._’ Audio adjustment

l- Move the oscilloscope probe to terminal A 3.

: 2- Maintain on the TP 1 the IF signal with modulated audio carrier.

_”. . . .::.
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; .: 3- Adjust P 2 so as to obtain on the A 1 terminal the signal

VA 3 = 2.2 + 0.2 vpp = 0.78 2 0.07 V RMS.
‘: ..

AFC adjustment

l- Bias the AFC output by means of two 100 kOhm resistances ; one
towards +12V and the other towards earth.

2- Connect a voltmeter to AFC output pin A 12.

3- Adjust L45 for an intermediate value (approx. 2V) in range of

values that go from +12V to 0 V.

*. .-

::
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Adjustment of the AGC voltage for RF unit
‘.

l- Connect a voltmeter to TP 5.

2- With the signal at 15 mV video IF, adjust P 1 until voltage is

reduced to 8V.

Correspondence between TP (test point) and wiring diagram

TP 5 = R50 - 51 node
TP 1 = L20 - 24 node

. *. .-

-1 g-
PCB BS 399

Denomination .. Luminance-chrominance and video

output amplifier.

Adjustment procedure

Preliminary operations

Check that the p.c.b. is correctly supplied: +i2.6V + 25OmV on contact

F12; +2OOV DC + 1OV on contact G5; +2.2V DC + 1OOmV on contact Fl;
12 Vpp on contact F14; 160 Vpp on contact G2; 11 Vpp on contact FlO.

Brightness and contrast controls to maximum (adjustment on remote

control when provided).
Colour saturation to minimum.
Grey scale signal in antenna. Correct tuning.
Adjust black-level potentiometers P105-P107-P109 to max. (clockwise)
Adjust gain potentiometers, ~104-P106-P108 to max. (anticlockwise).
Oscilloscope with attenuated probe on contact F2.
Check that the signal present on this point has a total width of
2.65 Vpp.

Operations

Oscilloscope's probe on red output (H4).

Adjust P105 to set the reference level (see figure 4) to 170V DC.
Oscilloscope's probe on green output (H2).
Adjust P107 to set the reference level to 170V DC.
Oscilloscope's probe on blue output (Hl).
Adjust PlO9 to position the reference level to 170V DC.
Colour bar signal in antenna. Correct tuning. Saturation to max.
Oscilloscope's probe on TP102. Apply a 1 V DC voltage to TP103.
Adjust LlOl for max. amplitude of signal displayed.
Suppress voltage applied to TP103.
Plug in jumper S103. Disconnect SW102.
Adjust Cl23 for minumum bar horizontal drift.
Disconnect S103. Reconnect SW102.
Test 3 signal (delay) in antenna.
Oscilloscope's probe on red output (H4).
Adjust PI03 and, if necessary, L104-L105 so as to perfectly align the
bottom portion of the signal displayed.
Test 2 signal (phase) in antenna.
Adjust L102 for best superimposition of the two wave shapes displayed.

. *. .-
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-2o-
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Grey-scale alignment
. . ..,
:

Grey-scale signal in antenna (or an equivalent signal). Saturation to

minimum. Correct tuning. Disconnect SW501.
Slowly adjust P551 so as to obtain a horizontal line slightly lit
(it's advisable to operate in low environmental lighting conditions).
Keeping as reference the colour of the prevailing electron gun of this
line, accurately adjust black-level potentiometers of the other two
electron guns (P105 for red, P107 for green, P109 for blue) until the
i .’ horizontal line is perfectly white.
Adjust P551 up to the point in which the white line,fades out
(cut-OFF).
Reconnect SW501.
If a predominance of a colour is noticeable on the screen, eliminate
it by re-adjusting the black-level potentiometer of the relevant
electron gun involved.

J
-_-_- 1 7 0 V D C

Fig. 4

-21-
 .:.
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.‘, :: 7
:. .-. PCB BS 396

.. Synchro. separator and pin-cushion

Denomination
correction.

Adjustment procedure

Synchro. separator alignment

- With test picture to antenna and a jumper on S 401, adjust P 401

until the picture slowly drifts horizontally. ’

- Disconnect bridge S 401.

Pincushion alignment

- Adjust P 402 until the external vertical lines of the test picture
are straight.

- Adjust P 403 to obtain a correct horizontal amplitude.

PCB BS 393

Denomination : Picture tube

Adjustment procedure

SW 551-552-553 Switches for exclusion of picture tube electron

guns.

P 551 Grid 2 adjustment of picture tube.

P 552 Focus adjustment.

PCB BS 417

Denomination .. Power supply

Adjustment procedure

Adjust P 301 to obtain +150 V DC at terminal N 5.

Adjust P 303 to obtain +12.6 V DC at terminal N 1.
Make sure that voltage at terminal N 3 and N 4 is +27 V DC 2 2% and, at
terminal N 6, +200 V DC _t 2%.

-22-
PCB BS 397

Denomination : Vertical deflection

Adjustment procedure

Test signal in antenna.

Adjust P 352 to obtain a correct frame synchronization.
Grossly adjust vertical centering (P 354), vertical amplitude (P 353)
and linearity (P 351).
Adjust P 354 for correct picture centering. ’
Adjust P 353 to obtain a correct vertical amplitude.
Adjust P 351 to obtain the best vertical linearity.

*. .-

-23-
i
: TELETEXT TRANSMITTER

._:_,
(. .
./._,
..:,:

TELETEXT FUNCTIONS

TEXT - Switches the system into the teletext mode MIX - HOLD -
BOTTOM - CANCEL and STATUS become operative. The commands
for the brightness, volume, saturation, muting in the Text
mode are all operative and this is useful in MIX.and CANCEL
operations.

MIX - Superimposes teletext on to normal television programme on

the screen.

REVEAL - This command displays concealed information as long as the

button is depressed. (Used for quizzes, puzzles etc.)

TP-ON -' This allows an "Alarm Page 'I to be received at a predetermined

time. Select the page number required and press TP-ON.
TOO00 will appear at the top right hand corner of the
screen. Select the required "Alarm Time" using the numbered
keys. The figures will appear in white.
. *. .-

-24-
 Press the CANCEL button and the normal TV programme will
return with the Teletext page Header superimposed for 5
seconds. At the selected alarm time, the alarm page header
will re-appear. This page remains stored in the memory
until the TP-OFF command is pressed.

TP-OFF - Cancels TP-ON

HOLD - To retain the page selected. Hold will appear written in

green at the top right hand side of,the screen. To cancel
the command press TEXT - MIX - TP-OFF - CANCEL.

TOP - Displays the top half of the page in large characters.

BOTTOM - Displays the bottom half of the page in large characters.

Commands TEXT - HOLD - TP-ON - TP-OFF restore the mode into
the upper half page.

FULL - Restores the character size to normal.

CANCEL - This command suppresses the TEXT display, restores Video

picture while the system remains in Teletext mode, giving
the possibility of selecting:

- Pages - using TP-ON

- Alarm pages

- TEXT and MIX will cancel the command.

PICTURE - Returns to TV picture from Teletext mode.

1 -10 - Numbered keys (l-O/10) serve to select pages (3 digits) -

time (4 digits). If figures are incorrectly entered, the
full sequence must be completed before re-entering correct
figures.

STATUS - If in Video mode, the Station identity will be displayed

for 5 seconds. In the Teletext mode, the page number is
replaced by the station identity for 5 seconds.

-25-
Transistors used on teletext p.c.b.

Transistors Type Electronic functions

T 1 BC 548 B Video preamplifier

T2 BC 548 B Video preamplifier

T3 BC 548 B Video input signal switch

T4 BC 548 B T3 switch enabler

T5 BC 548 B Teletext synchro. switch

T6 BC 548 B Synchro. signal emitter follower

T7 BC 548 B Command inverter

T8 BC 548 B B signal emitter follower

T9 BC 548 B C signal emitter follower

T 10 BC 548 B R signal emitter follower

T 11 BC 548 B Blanking signal emitter follower

T 12 BC 548 B Brightness signal emitter follower

. _. .-
.-
.

-25-
ICs mounted on teletext p.c.b.

ICS Type Electronic functions

CI 1
rA 78 Ml2 C 12V stabilizer

CI 2 78 MO5 C 5V stabilizer
P
CI 3 SAA 1272 A Programmable adaptor for teletext

CI 4 SAA 5030 - VIP Teletext video processor

CI 5 SAA 5041 - TAC Teletext acquisition and control circuit

CI 6 SAA 5020 - TIC Teletext timing chain circuit

CI 7 SN 74 LS02N Two-input NOR

CI a SN 74 LS 83 AN 4 bit adder

CI 9 SN 74 LS 161 AN 4 bit synchro. counter

CI 10 SN 74 LS 161 AN 4 bit synchro. counter

CI 11 MCM 21 L 14 C 45 4096 bit static RAM

CI 12 MCM 21 L 14 C 45 4096 bit static RAM

CI 13 SAA 5050 TROM (GB) Teletext ROM character generator

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 BS 489 Teletext p.c.b.

This p.c.b. performs the following main functions:

- it receives the teletext information from video signal (digitally

transmitted during the vertical blanking interval;
- it decodifies the teletext information and transfers data into
memory (CI 11 and CI 12);
- it generates timing signals for displaying and reading data stored
in memory (CI 6);
- It converts data retreived from memory into video signals to be
forwarded to the CRT (CI 13);

- it supplies blanking and synchro. pulses to be forwarded to the TV

set synchro. separator when teletext information is diplayed.
The p.c.b. is supplied with +5V and +12V.

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TELETEXT-DECODER ADJUSTMENT

The teletext p.c.b. requires three alignment operations which are all
relevant to the video input processor SAA 5030.
These alignment operations eliminate influence of tolerances both Of
video input processor and of its peripherical components.
The adjustment procedure need not be repeated any more until no
component substitutions are carried out and until the same video input
processor is used.
1. Adjustment of the chronological position (phase) of synchro. pulses
Cronological position (phase) of vertical sinchro. pulses supplied by
the video input processor SAA 5030 is adjuted through trimmer PlT.
The video signal phase (TP8), and in particular the portion including
the vertical synchro. signal must be compared on the oscilloscope
against the output signal taken from contact 13 of IC SAA 5030
(TP 10).

The trimmer is adjusted so as to delay the leading edge of the video

signal pulse (on contact 13) 48 2 5 )H with reference to the start
of the vertical synchro. signal (wide pulses).
This position is shown in Fig. 1.
The leading edge of the vertical synchro. pulse must thus be at 3/4
of line on line 1 and at a l/4 of line on line 314 of video signal.

Video input signal

U n ll n n JU U'

Vertical synchro. pulse

from contact 13 of
IC SAA 5030

Fig. 1 - Adjustment for correct positioning of

vertical synchro. pulse.

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2. ADJUSTMENT OF QUARTZ CONTROLLED FREQUENCY

A Method

The free running frequency of the oscillator is adjusted by means of

a capacitive trimmer C26T connected in series with the quartz.
The oscillator is free running when pin 1 of SAA 5030 circuit is
directly connected to +12 V (jumper between TPl and TP2) and pin 7 is
connected to +12 V via a 5.6 M Ohm resistance (jumper between TP3 and
TP4).
Video signal (TP8) on oscillator is compared against sand-castle
pulse present on Pin 5 of SAA 5030 (TP 7).
Capacitive trimmer is adjusted so as to maintain ratio between the
two signals unchanged (i.e. find the position in which relative shift
between the two waves is less emphasized).
Remove again shortcircuiting jumper and 5.6 M Ohm resistance.
Oscillator free running frequency is encreased by means of this
resistance from approx. 0.5 kHz to over 6 MHz, this assuring that
signal quality detector provided in circuit SAA 5030 operates in the
best manner.

B Method

For capacitive trimmer adjustment it is also possible to use the same

teletext reproduction.
Once again it is necessary to connect the short circuiting jumper and
the 5.6 MHz resistance as described above.

By means of remote control the teletext decoder is switched to mixer

operation.
Page memory does not necessarily have to be occupied with a teletext
page, but it is possible to use randomly selected characters
contained in memory which are sufficient for adjustment by means of
reproduction on the screen.

Capacitive trimmer is adjusted so that characters occupy a fixed

position on the screen.
Remove once again the shortcircuiting jumper and the 5.6 MHz
resistance.
If, by means of capacitive trimmer adjustment, characters do not
reach a condition of rest, it is sufficient to adjust for minimum
character shift.

. . * ._
.-

-?C-
J
3. ADJUSTMENT OF OSCILLATING CIRCUIT COIL FOR DATA CLOCK

A) Tune to a TV station having teletext signals; the signal must be

sufficiently strong (>lmV) and free of reflections and
interferences of a certain intensity.
Select a teletext page with continuous data renewal and damp
signal until a few errors appear.
Adjust L4T so as to make character errors disappear or for the
least number of them.

B) Use a teletext generator having a pseudo-random sequence.

Connect the oscilloscope's probe to pin 18 of SAA 5030 (CLOCK
output) and synchronize it externally with clock signal of
teletext generator.
Adjust L4T for a stable clock signal.
Final check.
Select page III; check for completeness and exactness of the
heading line and of page characters.
Check functions of TELETEXT transmitter.

Testing of teletext p.c.b.

1) Check supplies:

a) 12~ + 5% (~~61; 280 mA

b) 5V z 5% (TP5); 380 mA

2) Test transcoder and transmitter

Depress in TV mode some programme selecting controls and check
exactness on display.
Always in TV mode visually check efficiency of analogical controls
(brightness, colour, volume muting, normal setting).
Check in text mode efficiency of all controls.

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 1
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‘: ADJUSTMENT OF RGB LEVELS ON TELETEXT P.C.B

Adjustment must be carried out before "white adjustment".

1) Adjust P4T and P3T on R and G so that characters reach the 100 V DC
level.

2) Adjust P2T on B so that the character reaches the 110 V DC level.

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Line blanking
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11OV DC____
(B level) _-_- 1OOV DC (R & G levels)

0 V DC

Fig. 2

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a. :‘. After white adjustment visually inspect that white characters have
correct tint, otherwise, retouch one or two of the potentiometers P2T,
P3T and P4T (reducing amplitude of dominant colours) so as to obtain
characters having correct white.

., .’ :
‘. :

-32-
 PRODUCT SAFETY NOTICE

Although the main chassis is insulated from mains, part of the power
supply chassis bears mains voltage. This therefore should not be
connected to earth during servicing.

Do not install, remove, or handle the picture tube in any manner unless
shatter-proof goggles are worn. People not so equipped should be kept
away while picture tubes are handled. Keep picture-tube away fron the
body while handling.
Before returning a serviced receiver to the customer, the service
technician must thoroughly test the unit to be certain that it is
completely safe to operate without danger of electrical shock, and be
sure that no protective device built into the instrument by the
manufacturer has become defective, or inadvertently defected during
servicing.
Therefore, the following checks are recommended for the continued
protection of the customers and service technicians.

INSULATION

Insulation resistance should not be less than 2 MOhm at 500 V DC

between the mains poles and any accessibe metal parts.

HIGH VOLTAGE

High voltage should always be kept at rated value of the chassis, no

higher. Operating at higher voltage may cause a failure of the
picture tube or of high voltage supply.

Furthermore, in no case whatsoever must the electrical circuit

providing the EHT be altered so as to prevent wrong voltage values
from causing ionizating radiations above those allowed by international
standards.

REPLACEMENT OF COMPONENTS

Some electrical components have special safety related characteristics

which are indicated on schematic diagram by the

Therefore, all components provided with this mark must be replaced with
original ones and their assembly must comply with the original assembly.

. .* .
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The Manufacturers reserve all legal ri&z to the exclusive

ownership of this document and hereby prohibit reproduction
or disclosure of the 8ame without their prior permission.

. . * ._
.-

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