TV & RADAR SYSTEMS (TC-335)

• PRACTICAL WORK BOOK

For Academic Session 2009

TV & RADAR SYSTEMS

(TC-335) For

T.E (TC)

Name:

Roll Number:

Batch:

Department:

Year :

Department of Electronic Engineering

NED University of Engineering & Technology, Karachi

LABORATORY WORK BOOK For The Course TC-335 TV & Radar Systems

Prepared By: Ms. Shakila Bint Reyaz

Reviewed By:

Mr. Tahir Malik (Lecturer)

Approved By:

The Board of Studies of Department of Electronic Engineering

INTRODUCTION

TV & Radar Practical Workbook covers those practical that are very

knowledgeable and quite beneficial in grasping the core objective of the subject.

These practical solidify the theoretical and practical concepts that are very

essential for the engineering students.

This work book comprise of practical covering the topics of TV circuitry and

Navigational Radar that are arranged on modern trainer boards. Above all this

workbook contains a relevant theory about the Lab session.

TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering

Telecommunications Laboratory

CONTENTS

Lab No. Dated List of Experiments Page

No. Remarks

1 Introduction to Radar Trainer 2-4

2 To familiar with operating principle Of Radar 5-13

3 To Measure the Target Range 14-24

4 To Observe the Echo Signal from the Target 25-26

5 To simulates faults (1) 27-30


7 Introduction to basic TV circuit signals 36-40

8 To perform measurement of synoptic panel 41-42



1

TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering gjjj

LAB SESSION 01

OBJECT:- INTRODUCTION TO RADAR TRAINER. COMPONENTS OF THE RADAR TRAINER:- The Radar Trainer mod. M702/EV consists of two units .

• External Unit (or Scanner Unit), and

• Internal Unit (including the Display and the schematic diagram).

All the used components are of professional type.

In detail:

• The External Unit, or SCANNER UNIT, includes the Antenna or the Dummy Load

(for the use in laboratory);

• The Internal Unit, or DISPLAY UNIT, includes all the control and management

section of the External Unit, and the monitor that displays the received and processed

information.

2


EXTERNAL UNIT (SCANNER UNIT)

TECHNICAL DESCRIPTION OF THE UNIT:-

ANTENNA:-

Antenna Type Horizontal opening Vertical opening Side lobes within + 10° from the main beam Side lobes beyond + 10° from the main beam Gain Rotation

1.8 feet, Radome Horizontally biased slotted waveguide 4.2° + 0.2° 25° + 2° > –18 dB > –20 dB > –23 dBi 22 rpm + 2rpm

TRANSCEIVER:-

PEAK POWER FREQUENCY RANGE Pulse Length

4kW 9410 MHz + 30 MHz 48 N.M. (Nautical Miles) Short (50ns): with PRF of 3200 Hz and Range from 0.75 to 3 N.M. Medium (200 ns): with PRF of 1600 Hz and Range from 3 to 12 N.M. Very Long (800 ns): with PRF of 500 Hz and Range from 12 to 48 N.M.

Receiver Front-end module Intermediate Frequency IF bandwidth Duplexer Noise image

Logarithmic, of solid state Microwave integrated circuit 60 MHz 20 MHz on short and medium pulses 4 MHz on long and very long pulses Ferrite circulator with solid-state limiter diode < 4.0 dB

3


INTERNAL UNIT (DISPLAY UNIT) DESCRIPTION:- Type Liquid-Crystal Display of 15”, 1024x768

pixels, 16 million RGB colours of active TFT (Thin Film Transistor) matrix, dot pitch of 0.297mm

Presentation P.P.I. ASTER scanning with radar video continuously shown and refreshed.

Video High resolution of 800 x 600 pixels, colours with 16 levels.

Scales Nautical Miles: 0.065-0.125-0.25-0.5-0.75-1.5-3- 6-12-24-48 N.M. Kilometers: 0.25-0.5-1-1.5-3-6-12-24-48-96 km

Fixed marks 0.031-0.0625-0.125-0.25-0.5-1-2-4-8 N.N Minimum Range 15 metres Discrimination The higher between + 6m and 0.8% of the

scale being used. Mini ARPA function Autotracking up to 12 targets with manual

initialization. Calculation of speed, CPA and TCPA course.

POWER SUPPLY DESCRIPTION:- General power supply of the Radar trainer 230 Va.c. -50 Hz , or others upon request. Supply voltage of DISPLAY UNIT Coming from a power supply inside the

Trainer and ranging from 10.4 Vd.c. to 40 Vd.c (< 80 W)

Supply voltage of SCANNER UNIT coming via the interconnection lead from the DISPLAY UNIT

OPERATING CONDITIONS:-

SCANNER UNIT From -25°C to +70°C, 95% max humidity DISPLAY UNIT From -15°C to +55°C, 95% max. humidity

4


LAB SESSION 02

OBJECT:- TO FAMILIAR WITH OPERATING PRINCIPLE OF RADAR.

BASIC DIAGRAM:- The Radar Trainer mod. M702/EV is equipment that uses the state-of-the-art

technologies in the field of digital processing to optimize the performance of the radar

in all the scales.

The abilities of target discrimination have been emphasized even in unfavourable

conditions of sea and rain clutter, and the noises due to emissions of other radars have

been minimized with a specific circuit. Moreover, using sophisticated correlation

techniques will lead to improve the Signal/Noise (S/N) ratio, with the advantage of

improving the abilities of target detection.

The Radar Trainer also includes the Mni Arpa function enabling the automatic

tracking of targets (up to 12 targets at the same time) after they have been acquired

manually.

This Radar can be divided into several sections included in the SCANNER UNIT and

in the DISPLAY UNIT, as it is shown in the fig.

5


6

TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering The SCANNER UNIT (or External Unit) includes the circuits performing the

following functions:

• Generation of microwaves

• Emission of pulse microwaves

• Reception of the energy reflected by echoes

• Rotation of the antenna

The DISPLAY UNIT (or Monitor Unit) includes the following sections:

Radar Interface that:

• Converts the received radar signal into digital form

• Eliminates the interferences

• Generates an image (radar image) that can be displayed on a Monitor

Microprocessor unit that:

• Reads the data/commands typed on the keyboard

• Converses with navigation instruments (gyrocompass, GPS,

LORAN,...)

• Controls all the radar sections generates a synthetic mage that will be

superimposed on that determined by the radar signals to increase the

number of information supplied to the user of radar

Liquid-Crystal Display (LCD) that shows the radar image and the

information coming from the CPU

Power supply unit that outputs all the direct voltages for powering the

radar circuits (including the SCANNER UNIT) and any external

accessory.

Timing the Transmission and Reception Circuit:- The operation of all circuits of the Radar is tuned on two pulse signals, both generated

by the antenna rotation: they are:

• ACP (Antenna Clock Pulse) signal, and

• HL (Head Line) signal.

The first is the reference clock signal for timing the transmission and reception

circuits, the second is the position reference for showing the echoes on the display.

7

TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering The digital image of Radar echoes (a complete antenna revolution) is

composed by 4096 beats (or sweeps) (fig. 2). Each beat is started by a

command from the transmission trigger, obtained by an ACP signal.

The ACP signal of this Radar is the clock signal timing all transmission and reception

phases.

The different phases can be explained with reference to the fig. 3:

• An optical encoder mounted on the antenna generates 2048 pulses per

revolution (ACP signal)

• A frequency multiplier / divider controlled by the CPU generates the PRF

frequency (Pulse Repetition Frequency) whose value depends on the range

(3200/1600/800/500Hz)

• The trigger TRG pulses for transmission are extracted from the PRF

signal.

• At each trigger a beat starts, during which the following operations are

carried out:

o Generation of transmission pulses (their duration τ depends on the

range) for driving the Magnetron

o As it receives the transmission pulses, the Magnetron emits the

oscillation

o After emission, the Radar switches to reception mode and activates the

receiving circuits

o The echoes are received during the reception gate, and then they are

processed in the Radar Interface section.

8


Diagram

9


Processing Echoes and Generating the Radar Image:-

The echo signals received by the antenna reach the DISPLAY UNIT (SMT card

visible on the Panel of the Radar Trainer) to be processed by the Radar Interface.

The Radar interface carries out the functions indicated in the time chart of the figure,

that is:

• Acquisition of echoes (ACQUISITION)

• Digital processing (PROCESSING), and

• Generation of radar image (SCAN CONVERSION),

in sequence, at every “beat”, that is at every transmission/reception interval.

Diagram

10


DISPLAY UNIT:- The DISPLAY UNIT represents the hear of the Radar where signals are processed

completely; it consists of several sections.

It is interconnected with the SCANNER UNIT via the multi polar cable mod. CB-20

with length of approximately 15m.

The DISPLAY UNIT receives the following radar signals:

• VIDEO

• Trigger (TRG)

• ACP

• HL

From the scanner unit; then these signals will be acquired and processed.

Analyse the different phases already mentioned, that is: Acquisition – Processing –

Scan conversion, following the VIDEO signal that includes echoes, that is

information to be display.

In detail, observing the schematic diagram of the trainer will lead to the examination

of each functional block (fig.).

11


ACQUISITION OF ECHOES (ACQUISITION):- During the GATE1 the VIDEO signal is processed in analog from, converted into

digital signal and then it is processed digitally.

Observe the various functional blocks:

• The input stage PROGR. AMP is a variable-gain amplifier, controlled via

hardware during the testing of the trainer: this stage amplifies the entering

analog signal.

12


SCANNER UNIT:- The SCANNER UNIT (or External Unit) includes the following circuits:

• Transmission circuits

• Reception circuits

• Antenna and circuits for moving the antenna

A general block diagram of the Antenna Unit is shown in the fig. , whereas the figures

A and B show the used components.

13


LAB SESSION 03

OBJECT:- TO MEASURE THE TARGET RANGE. SWITCHING THE RADAR ON:- Antenna:- Necessary operations:

• When the radar is used indoors or in a laboratory, check that the

SCANNER UNIT includes the dummy antenna (labeled as DUMMY

LOAD).

• On the contrary, when the radar is used outdoors, check that the

SCANNER UNIT includes the actual antenna (labeled as DPLOYYRF

SNYRNNS).

Note that the actual antenna is a slotted waveguide (on the emission side), whereas the

dummy load is a “Closed” waveguide.

When the antenna must be replaced with the dummy load (and vice versa), it is

necessary to remove the 5 upper screws of the antenna and the 3 screws of the internal

frontal part of the same antenna.

CONNECTIONS:- Before powering the Trainer, check the following connections.

Check on the right side that:

• There is the power cord and that this is inserted correctly into the power

socket (MAINS AC)

Check on the left side that:

• That connector of the lead of the SCANNER UNIT is connected with the

socket J3.

• The connector of the lead of the LCD DISPLAY is connected with the

socket J14.

14


• The connector of the lead of the keyboard (CONTROL PANEL) is

connected with the socket J11.

• The power cord of +24 Vdc is connected with the socket J1

• The connector enabling the programming menus (PROGRAMMING

KEY, Installation Menu and Manufacturer Menu) – when available – is

connected with the socket J5.

• The connector for programming the number of revolutions of the motor

(MOTOR CONTROL KEY; this radar allows only one number of

revolutions) is connected with the socket J13.

• The connector enabling the radar power supply is connected with the

socket J16.

• the connector enabling the starting of the radar is connected with the

socket J15: this is generally used for the remote switching on (pins 1 and 2

bridge)

SWITCHING ON:- The trainer must be powered through the main switch available on its right side.

When the trainer is switched on, a sound signal can be heard.

Wait for some seconds: during this time some data of the radar (software version,

model, date…) are displayed and some self-diagnostic tests (RAM, graphic memory,

dual port, serial port….) are carried out and the respective results are displayed.

Each result may be positive (indication: PASSED) or negative (indication: ERROR).

Al last the final window is displayed and the warm-up phase of Magnetron (WARM-

UP) starts: it takes some minutes.

After this phase, press the key TX starting the transmission.

15


GRAPHIC PRESENTATION:- The screen (fig.1) enables the graphic presentation of various data at the same time,

and it can also enable different menus.

Note that the continuous refreshments of firmware could modify the following indications.

Here is the information being available at the same time:

• Scale being used

• Rings (when enabled)

• Data on any target or waypoint (WP)

• Active functions (pressing ENT on the acronym identifying the function

will enable or disable the same function): Echo Stretch (ES)

Short or Long pulse ( ) Interference Suppression (IR) Alarm Plot (when Active) ……..

• Position of the cursor: Lat, Long or Range and Bearing

• EBL (Electronic Bearing Line, electronic detection)

• VRM (Variable Range Marker)

• Polygonal Guard Zone

• Sectional Guard Zone

• Head Line (HL)

• Data of the ship: Latitude (lt), Longitude (lg), speed, Course Over Ground

(COG)

Speed can be selected among:

o SOG (Speed Over Ground or actual speed): the speed value is

extracted from the NMEA message

o LOG: the speed value comes from a pulse log

o VHW: the speed value comes from a serial log: position the cursor in

the point where the value s represented and press ENT.

This data item is valid if the colour is green.

• Indicators of: FTC, STC, GAIN and TUNE

• Menu bar

16


• Function keys

The cursor can be displayed as:

o A cross if it is inside the central zone of the display ( + )

o An arrow if it is used outside to enter the various menus.

Diagram

17


FUNCTIONAL DESCRIPTION OF CONTROLS:-

Commands can be set and executed through the PANEL CONTROL keyboard or

some available Menus that can be enabled on the screen.

This section will explain the following procedure:

• Position the cursor on the desired element and press ENTER to select

keys, fields, radar targets and menu items;

• The value of the function can be varied with the keys–, + and ENTER

• Pressing CLR and ENTER will clear a function after this has been

selected with the cursor.

SCALE CHANGE:- Selecting the field Range and pressing the keys + and -, or UP or V DOWN

(RANGE) will change the presentation scale.

The scale change implies that the radar modifies the PRF, the pulse width and the

spacing between the fixed marks for a better operation. After this operation it will be

necessary to adjust the gain, the tune and the STC, if necessary.

GAIN:-

This control allows amplifying the video signals so that the highest number of echoes

of the present targets can be displayed on the screen. This adjustment is carried out

with the GAIN control and its visual effect consists in modifying the dimensions of

the echoes displayed on the radar.

It is important that this adjustment leads o lie presence of background noise that

enables the discrimination of targets, especially on the open sea where echoes are very

faint.

When low scales are used, echoes could disappear for an excessive control of the gain

because they can be confused with noise.

In this case:

• The gain must be reduced

18


• The STC control must be used to clean the centre of the screen from the

sea Clutter.

STC:-

This control enables to reduce the echoes due to targets near the radar, in detail for the

sea waves.

This adjustment is carried out with the STC control.

It is typically used in the low scales to remove the Clutter and consequently to clean

the centre of the screen.

Selecting some setting from the VIDEO menu (refer to the description indicated here

below) will limit the effect of STC up to 3.5, 5.5 or 7 N.M.

An excessive insertion of this control can lead to clear the faintest echoes available in

the central position of the screen.

TUNEA/M:- This control enables to adjust the tuning of the receiver according to that ot the

transmitter.

Any scale can be used.

The adjustment is carried out with the key TUNE; pressing the keys + or— will lead

to the maximum tuning indication on the screen.

This is very important because it can compromise the visibility of targets, especially

on the open sea when there are no visible echoes.

A better result can be obtained by the control of the gain combined with the tuning

control.

The tuning control may be:

• Manual, or

19


• Automatic, and the key Tune cannot operate in this mode. Moreover the

scale change or the passage from the Stand-BY mode to ON require some

instants because the reception circuit must be tuned again with the

transmission circuit.

FTC:- This control enables to reduce the effect of weather perturbations such as rain, rainy

clouds, fog, snow…

This adjustment is carried out with the key FTC and the keys + or —.

An excessive insertion of this control can lead to clear the echoes due to targets.

GUARD ZONES:- Two types of guard zones: polygonal and sartorial, can be inserted through the Popup

Menu.

How these zones can be drawn is described later on.

A guard zone is displayed on the screen with blue colour.

More than three guard zones (either polygonal and sectorial) cannot be inserted.

TARGETS:- Targets can be inserted through the Popup Menu.

How a target can be inserted is described later on.

Selecting a target several times will lead to display the data concerning it.

The data that can be displayed are:

• Latitude (it) and longitude (ig)

• Relative position: distance (dst) and detection (ru)

• Course and speed

• Time-distance-angle of the closest point of approach (TCPA, CPA)

• Collision course and collision time (RCOL, TCOL, TIME)

This function is enabled if the GPS and the compass send the data to the radar:

Latitude, Longitude and North-Up are necessary.

20


WAYPOINT:- Waypoints (WP) can be inserted through the Popup Menu.

How waypoints can be inserted is described later on.

This function is enabled if the GPS and the compass send the data to the radar:

Latitude, Longitude and North-Up are necessary.

ANTICOLLISION ALARM:- Anti collision alarm can he set through the Popup Menu. It is necessary to set the

following limits:

• TCPA (Time to Closest Point of Approach) that represents the shortest

time of approach to any target being tracked in collision course

• CPA (Closest Point of Approach) that represents the shortest distance of

approach to any target being tracked in collision course.

If a target being tracked takes a position below the thresholds set before, then its data

will be displayed and a sound alarm can be heard.

DETECTION (EBL):- This control enables the rotation of the detection lines displayed on the screen.

These lines are two (active one at a time) and they supply the detected data on the

same screen.

Enable this function:

• By selecting the fields EBL1 or EBL2

• By selecting the keys + or — to rotate the line or by selecting a point on

the screen

DISTANCE:- This control enables to display the moving distance marks on the screen. These marks

are two (active one at a time) and they supply the detected data on the same screen.

Enable this function:

• By selecting the fields VRM1 or VRM2

• By selecting the keys + or – to shift the moving mark or by selecting a

point on the screen.

21


SHIFTING THE CURSOR:- Selecting any point on the screen will position the cursor and display the value of

distance and detection with respect to the position of the ship. Selecting the data field

will enable to change the data presentation from relative (distance/detection) to

absolute (latitude/longitude).

CLEARING THE HEAD LINE (HL):- The Head-Line command enables to clear the head line from the screen only when the

corresponding key is pressed.

STAND-BY/TRANSMISSION:- This command enables to pass from the stand-by mode (ST.BY) to the Transmission

mode (TX), and vice versa.

The stand-by condition is displayed at the centre of the screen.

The key ST.BY/TX used by this control is not active during the WARM-UP phase

lasting for approximately two-three minutes.

CHANGING PULSE:- This control that can be enabled on some scales allows to modify the duration of the

transmission pulse.

When using this function consider that:

• A long pulse enables a safer detection, whereas

• A short pulse enables a better definition (or detail) of the radar image

ECHO STRETCH (ES):- The Echo Stretch (ECHO STR.) function can be enabled on all the scales and it

allows to stretch the video signals displayed on the screen. It can be enabled or

disabled by the selection of the field ES available on the screen.

It is possible to select:

• ES: no Stretch applied

• ES1: weak Stretch

• ES2: strong Stretch

22


INTERFERENCE SUPPRESSION (IR):- The Interference Suppression function enables three levels of suppression of the

interferences affecting the radar image.

It can be enabled or disabled by the selection of the field IR available on the screen.

It is possible to select:

• IR: no interference-rejecting level

• IR1

• 1R2

• 1R3: maximum interference-rejecting level

OFF CENTER:- The control Off-Center enables to shift the centre of the display on the position

selected by the cursor.

It can be enabled or disabled by the selection of the field Off-center available on the

screen.

MAN OVER BOARD (MOB):- The function of “man over board” can be enabled directly or from the Menu bar ACQUIRING TARGETS:- Selecting ACQ.TARGET will enable the function of acquisition of targets.

The display of the ACQUIRE TARGET function is enabled. Now select it to acquire

the targets from the radar image. Pressing the same key or the key ENTER will stop

the acquisition and the message ACQUIRE TARGET will disappear.

DATA ON TARGET:- Selecting INFO OBJECT will enable the function of target data.

The display of the INQUIRE OBJECT function is enabled.

A target can be selected to display its data.

A further selection enables the display not off center.

The selected presentation will be confirmed when the key ENTER is pressed and the

message INQUIRE OBJECT disappears.

23


NAVIGATION MODE:- Clicking on this square will select the following different navigation modes:

• HEAD UP

• NORTH UP

• COURSE UP

FREEZE:- The Freeze control enables to freeze the radar image displayed.

CLEAR (CLR):- This control enables to clear the choice carried out.

24


LAB SESSION 04

OBJECT:- TO OBSERVE THE ECHO SIGNAL FROM TARGET. ECHO SIMULATION:- THE ECHO SIMULATOR will generate a simulated echo that can be shifted on the screen with the Angle and Distance controls. In detail, this simulation concerns the presence of an echo that can be shifted radially (angular distance with respect to the course) and lengthwise (distance from the ship) This electric signal is sent to the Video output (T P 26) in synchronism with the trigger pulses. It can be enable when the radar is used in laboratory (indoors) where there are not actual echoes. When the Mini ARPA function (Popup Menu, function Acquire Target) must be used ,it is recommended: • to use the scale of 6 N.M. • to adjust the gain at a value not too high nor too low so that the displayed target

can be contained in the square catching symbol • wait for some sweeps so that the target is caught and the square symbol

becomes green • adjust one of the (Angular or Radial) directions very slowly so that the

“slow” shiftment of a boat is simulated: a line indicating the course direction will appear on the target, whereas its length is proportional to the speed of the same boat.

25


Figure

Echo signal received from target.

26


LAB SESSION 05

OBJECT:- TO SIMULATE FAULTS (1).

FAULT SIMULATION:- FAULT SIMULATION TEST POINT FOR POWER SUPPLY TP1 Direct supply voltage available across the input of the switching power supply.

It is equal to the voltage applied to the input JI of the main AC/DC converter. A voltage of approximately +24 Vdc equal to the rated voltage can be measured.

TP2 Direct supply voltage available for the auxiliary outputs JA and JB.

It is equal to the voltage supplied by the auxiliary DC/DC Converter. A voltage of approximately +12 Vdc can be measured.

TP3 Direct voltage coming from one of the sockets of the secondary winding of the

transformer T1. A voltage of approximately +32 – 35 Vdc (rated voltage: +36 Vdc) can be measured.

TP4 Use a Digital Volt Meter (DVM) connected with the test points and with the

relevant ground. Direct voltage coming from the one sockets of the secondary winding of the transformer T1 for powering the motor of the Scanner Unit. A voltage of approximately +24 Vdc can be measured only in TX mode.

TP5 Use a Digital Volt Meter (DVM) connected wit ht he test points and with the

relevant ground. Direct voltage coming from one of the sockets of the secondary winding of the transformer T1n for powering the motor of the Scanner Unit after the motor control key and the protection fuse. A voltage of approximately +24 Vdc can be measured only in TX mode.

TP6 Direct voltage coming from one of the sockets of the secondary winding of the transformer T1. A voltage of approximately – 14 / -18 Vdc (rated voltage: - 12 Vdc Can e measured).

TP7 Regulated direct voltage coming from one of the sockets of the secondary

winding of the transformer T1…….. A voltage of +5 Vdc can be measured.

27


TP8 Regulated direct voltage coming from one of the sockets of the secondary

winding of the transformer T1. A voltage of approximately +12 Vdc can be measured

CPU:- TP9 Supply voltage of the buzzer coming from the CPU.

When the alarm is enable, voltage of approximately +5 Vdc can be measured. A voltage of +12 Vdc is available in rest condition.

TP10 (RX) DATA signal available on the serial port J11, coming from the control board of the CPU. When commands are sent via the keys, signal packages included between -8 and +8 Vdc are displayed.

28


TP11 (TX) DATA signal available on the serial port J11, coming from the Control

Board of the CPU. AS the trainer is switched on, signal packages ranging from -8 to +8 Vdc are displayed.

VIDEO SIGNAL:-

TP12 H SYNC signal available on the Video port with output J14, supplied by the transceiver to the output. This is the horizontal synchronism signal supplied to the LCD controller, with width of approximately 3.8 Vpp and frequency of 37.5 kHz.

TP13 V SYNC signal available on the Video port with output J14, supplied by the transceiver to the output. This is the vertical synchronism signal supplied to the LCD controller, with width of approximately 3.8 Vpp and frequency of 60 Hz.

29


TP14 R Signal available on the Video port with output J14, Coming from the Video Driver. It is the red component of the RGB video signal supplied to the LCD controller, with width of approximately 0.5 Vpp and frequency equal to the (horizontal) line frequency.

30


LAB SESSION 06

OBJECT:- TO SIMULATE FAULTS (2). SIMULATE FAULTS :- TP15 G signal available on the Video output with width J14, coming from the video

driver. It is the green component of the RGB video signal supplied to the LCD controller, with width approximately 0.5 Vpp and frequency equal to the (horizontal) line frequency.

TP16 B signal available on the video port with J14, coming from the video driver. It is the blue component of the RGB video signal supplied to the LCD controller, with width of approximately 0.3 Vpp and frequency equal to the (horizontal) line frequency.

31


SIGNALS OF THE MOTOR CONTROL / MODULATOR (SCANNER UNIT):-

TP17 HL signal available on the connector J3, coming from the sensor installed on

the mast of the antenna and sent to the CPU. This pulse signal has a width of approximately +3.7 Vdc and repetition period of 2.84 seconds.

TP18 AC signal available on the connector J3, coming from the encoder of the antenna motor and sent to the CPU. This pulse signal has a width of approximately +5 Vdc and frequency of approximately 730 Hz.

TP19 Stand-By/TX control signal available on the connector J3, coming from the CPU to the Modulator of the SCANNER UNIT. This is a voltage of approximately +12 Vdc in stand-By condition and it is almost to 0 (approximately 0.7 Vdc) in TX mode (Rader on).

TP20 TRG signal available on the connector J3, coming from the CPU to the

Modular o the SCANNER UNIT. This pulse signal has a width of the approximately +3 Vdc and a repetition period depending on the used scale.s Here as the available values - 513 µs from: 0.062 to 1.5 N.M - 610 µs: 3 N.M

32


- 1.25 ms: from 6 to 12 N.M - 2 ms: from 24 to 48 N.M

TP21 TRG RETURN signal available on the connector J3, supplied by the CPU and

coming back to the CPU after arriving at the SCANNER UNIT. This pulse signal has a width of approximately +8 Vdc and a delay between TP21 and TP20 depends on the length of the cable. The fig. 6.12 shows the time different the pulses of the TRG signal and of the trigger return signal.

TP22 Signal RAD 0 available on the connector J3, coming from the CPU to the Modulator of the SCANNER UNIT. This is a voltage depending on the used scale that modifies the duration of the trigger pulse. Here as the available values: - 0.7 Vdc: from 0.062 to 1.5 N.M - 6 Vdc: 3 N.M - 0.7 Vdc: from 6 to 12 N.M - 6 Vdc: from 24 to 48 N.M

33


TP21 Signal RAD 1 available on the connector J3, coming from the CPPU to the Modulator of the SCANNER UNIT. This is a voltage depending on the sued scale that modifies the duration of the trigger pulse. Here are the available values: - 0.7 Vdc: from 0.062 to 1.5 N.M - 6 Vdc: from 6 to 48 N.M

TP24 Signal MAG 1 available on the connector J3, coming from the Modulator of the

SCANNER UNIT to the CPU. It can vary according to the used scales and it is also used to detect faults in the transmission circuit. The available in the values are approximately: - 6 Vdc, in TX - 0 Vdc, in Stand-By

SIGNALS OF FRONT–END/RECEIVER (SCANNER UNIT):-

TP25 TUNE signal for controlling the tuning of the Front-End. The Auto (automatic) mode will enable to measure a level depending on the temporary condition to get the according to the on the contrary, the measured level is variable according to the set-up and it range from -10 to -13 Vdc, in manual tuning.

TP26 VIDEO signal by the receiver.

Using the echo simulator, selecting the scale of 6 N.M and positioning the target at the end of the scales will lead to the signal shown in the fig 6.13 (after a paper adjustment if the oscilloscope). The figure has been recorded when the antenna passes onto the position, but it is displayed only on that moment. Modify the distance of the target and note how the distance between the target and the ship (on the monitor) is proportional to the time distance seen on the oscilloscope between the sync pulse and the echo signal.

34


TP27 Signal TUNE IND output by the receiver. This level depends on how much the receiver is tuned wit h the transmitter. The fig. 6.14 shows the comparison between the signals of TP27 (in lower position) and of TP25 (YUNE). In detail, it shows the passage from the manual mode to the automatic mode with the result of tuning optimization. The fig. 6.15 shows the signal of TP27 when passing from AUTO to manual, and to AUTO again.

TP28 Signal TUNE REG entering the receiver. This positive voltage (ranging from 0 to 8 Vdc) will modify the tuning. It is necessary to enter the radar programming to vary it (it is used during the service).

35


LAB SESSION 07

OBJECT:- INTRODUCTION TO BASIC TV CIRCUIT SIGNALS.

IF SIGNALS:- The IF spectrum of frequencies is fed through a symmetrical path from the tuner pins 11 and 10 via the filter F901 and the Surface Acoustic Wave filter F906. The signal formed by the Surface Acoustic wave filter is applied symmetrically to pins 45 and 46 of the signal processor. The demodulation of the CCVS signal is carried out in a product demodulator. The required demodulator circuit F130 is connected to pin 2 and pin 3.

The demodulated signal passes through an amplifier and is then present at pin 7 of the IC (BB). The IC identifies the synchronising signal internally and for this reason, feedback of the line flyback pulse for gating purposes is not necessary. Corresponding to the synchronising signal level a control voltage is generated. This control voltage first acts on the controlled input amplifier of the M. Via pin 49 a reference threshold URV is set. Below this threshold, only the input amplifier of the IF is regulated. If the threshold is exceeded, the control voltage Ut is applied from pin 47 to the tuner. Pin 47 is an o n collector output. Ln uncontrolled condition, the voltage is approximately 5V. With increasing input amplitude the AGC level decreases. The direct voltage for automatic frequency control (AFC) is generated in the demodulator. Ping feeds out this signal as a current signal. When the received frequency increases, the control voltage for AFC decreases. The processor IC850 evaluates the signal and fine tunes the tuner accordingly. The demodulated signal is examined by the sync detector for the presence of synchronising signals.

36


If no such signals are present, the IC 150-(4) switches to "Low".

By this level the processor IC850-(33) can identify that the coincidence signal is missing and mutes the sound.

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TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering CCVS SIGNAL:- The demodulated CCVS signal leaves 1C150-(7), TDA8362A, as a baseband signal together with the sound-IF. In the following path, the sound signal is separated from the CCVS signal. After the transistor CT92 I and the sound trap F923 and F924 the signal path

divides.

Via the transistor CT 110 and 1C2807 (optionally) it is fed through to the videotext decoder IC850-(30) as F B A S s c signal, and via the transistors CT963, CT962 it is supplied to the Scant socket pin 19. At the signal source switch IC 150-(13), the signal is present as F B A S ( C C V S ) . The second input of the signal source switch pin 15 is connected to the Scart socket pin 20.At IC I 50-(16), the processor IC850-(42), voltage U V Q , transistor CT840 decides as to whether the signal from the tuner or the external signal is processed EXTERNAL CCVS SIGNAL:- At the signal source switch 1C 150-(15) either an external CCVS signal from the Scart socket or the RF-CCVS signal is present. The voltage Uvo at IC! 50-(16) decides which signal shall be passed on, the CCVS signal from the Scart socket or else the RF-CCVS signal. IC 150-(16) "Low", the internal signal is selected; IC 150-(16) "High", the external

signal is passed on.

Attention: if the option "Decoder On" has been selected the TV expects the signal to come from the Scart socket. However the CCVS signal from the tuner can be measured at output pin 19 of the Scart socket.

SOUND IF:- After the ceramic filter F926, the sound signal is superimposed at IC 150-(5) on a direct voltage for setting the volume level. Demodulation is effected by a PLL demodulator. In one path, the demodulated and uncontrolled AF signal is fed out at IC 150-(1), it is then amplified by the transistors CT917, CT916 and passed on to the Scart socket. In another path, the demodulated and controlled AF signal is present at IC 150-(50) and is fed to the AF-IC TDA7233. LUMINANCE AND CHROMINANCE SIGNAL:- Calibration and control is effected automatically during the frame blanking period. The signals are adjusted by a positive or negative current entering the integration capacitor CC 177 at IC 150-(12). During the scanning period the control voltage is clamped. The luminance signal passes through the colour trap integrated in the IC. The delay line provided in the IC is used to correct delay time differences between the luminance and chrominance signal. The colour transient improvement (peaking) which follows is also realized in this IC. For this, the steepness of the leading and trailing edges of the Y-signal is improved.

38

TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering The internal chroma filter separates the chrorninance signal from the CCVS signal. A control circuit adjusts the amplitude of the colour signal for the chroma limiter and chroma control.

The resulting chroma signal is passed on to the colour demodulator.

From this chroma signal, the burst is separated which is used to synchronise the colour oscillator in phase and frequency. The quartz establishes a fixed 4.43M-Iz frequency for the colour carrier at pin 35. The quartz is controlled by an internal PLL circuit. The correction voltage is integrated via the time constant at pin 33. By means of the colour carrier, the colour component signals are then demodulated and leave IC 150 as R-Y and B-Y signals at pin 30 and pin 31 respectively. Following the PAL delay at CIC 105 TDA4665 the two signals, B-Y and R-Y, are fed back to IC 150-(28), -(29) TDA8362A where they are clamped. Subsequently, the colour contrast is controlled at IC150-(26). In the matrix, the RGB signals are produced from the amplified signals and the Y-component.

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TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering SECAM SIGNAL PATH AND AUTOMATIC PAL-SECAM SWITCHING:- The chroma signal of approx. 300mV for the SECAM-IC110 is present at IC 150-(27). On SECAM mode, a voltage between 5.6V .. 5.8V is applied to IC 110-(16). When the IC 110 identifies the SECAM standard from the chroma signal at pin 16, a current source at pin 1 is activated and sends a SECAM identification to 1C150-(32). As soon as IC150 too has identified SECAM, this IC sets pin 32 to 5V (1.5V on PAL). This direct voltage is superimposed either by a regular clock frequency on PAL, or by bursts at a frequency of 4.43MHz on SECAM. The IC 110 interprets these as an acknowledgement and switches the difference signal outputs R-Y and B-Y (pins 9 and 10) to 3.5V DC (1.5V on PAL). The difference signal outputs of IC 150-(30), -(31) are thus blacked. IC 110 now supplies the R-Y and B-Y signals. The difference signals are returned to IC 150 via the delay line CIC 105. The following path of these signals is described under Luminance and chrominance signal. On SECAM reception the DC Level is switched to 3.5V at IC 110-(l0). Via C T 1 1 5 , UPAL changes to "Low" (PAL = "High") and pP IC850-(1) is able to identify PAL or SECAM on ATS search (only FR variants). On OIRT reception (6.5MHz sound carrier), the search mode of the pP (UPAL) is switched over by CT915 via UAUDIO and CT 115. RGB SIGNAL PATH For contrast control of the RGB signals, IC850-(23) generates a variable control voltage for the contrast controlling amplifier at IC 150-(25). Because too high a beam current may cause damage to the picture tube, the beam current is limited by this IC. The internal peak beam current limiting function is carried out in the peak white

limiting stage.

If the RGB signal exceeds 2.6Vpp, the internal peak white limiting function starts working and reduces the contrast.

The external peak beam current limiting threshold is 2Vpp approximately.

The average beam current limiting function reduces the setting voltages at IC 150-

(25) for the contrast.

After the brightness amplifier, the RGB signals leave the IC 150 and are passed on to the cathode amplifiers on the CRT base panel.

40


LAB SESSION 08

OBJECT:- TO PERFORM MEASUREMENT OF SYNOPTIC PANNEL

MEASUREMENT POINTS 0F THE SYNOPTIC PANEL:- This section contains the information to identify or to study the signals reported at

the measurements points of the synoptic panel. TV manufacturer are reported, with the addition of the references that are necessary to locate the point of the circuit where the signal is picked from. SIGNALS AT THE MEASUREMENT POINTS:-

Signal of the remote control receptor. Level normally 5V, with square waves that reach OV when the remote control is used.

TP1A - TP2A -

Reading keyboard signal. Normal level OV. It increases by pressing one of the keys. The microprocessor reads this level (PIN 32) through an internal C. A certain key and therefore a certain function corresponds to each one of the 4 possible levels

TP3A - Standby signal. Normally 12V with switched on W. It reaches OV on CPU control when the STANDBY key is pushed on the remote control.

TP4A - CPU reset. Normally high level (+5V).

Switching on TV with the mains switch, the signal becomes active withshort delay.

Analog signals of control of the image and of the sound generated by the CPU. Variable level from OV to +5V DC, respectively audio level (TP5A). Colour contrast (TP6A), brightness (TP7A).

TP8A - Synchronism composite signal (SYNC SSC), 5Vpp. The CPU uses this signal to produce the ON-SCREEN-DISPLAY (OSD) and the teletext.

TP9A - PWM signal emitted by the CPU to generate the DC level of control of the tuner tuning. Variable duty cycle square wave, 0-5V.

TP10A - B signal (blue) synthesised by the CPU to make the OSD appear on the screen.

TP4B -

TPSB - T

b

. Signal of the serial BUS I2C SCL (data synchronization clock). Aperiodic 5Vpp pulses. Bias voltage of the tuner Varicap (Tuning). Variable from OV to 30V DC according to the chosen station.

uner AGC. It is a continuous signal included between 0-5V. We observe level variations

y switching from a strong value to a weak one (by detaching the antenna).

41


TP 1C - Switching signal at the external Audio/Video socket. Normally OV, it becomes high (+5V) in AV.

TP2C - Logic pulse signal emitted from the CPU for the IF processor to qualify the emission of the OSD data from the screen. It is present only when the

menu appears (2Vpp). TP3C - The composite video signal available at the output socket AV. Level about

1 Vpp. TP4C - FBAS signal in input at IC 150 for the

source selection. Level about 1 Vnp. TP5C - Audio signal going out from IC 150 after the source selection.

TP1D - Luminace signal. Amplitude about 100mVpp with background 6V DC.

TP2D - R - Y signal after the delay and before the input at the colour matrix. Level about 50OmVpp. TP3D - B - Y signal after the delay and before the input at the colour matrix. Level

about 500mVpp.

TP4D - SB signal, i.e. the information of medium current of cathode ray.

TP5D - SSB (SW) signal. It is the feedback signal of the RGB amplifiers.

Amplitude about 2 Vpp.

TP1E - Demagnetization control logic signal (Degauss). Normally OV, it reaches

+5V during DEG.

TP2E - Logic level of supply starting. Normally +12V with switched on TV; OV

in standby.

TP3E - Logic level emitted from the CPU to check the source selection (int. or AV). Levels: 0 or +5V.

TP1F - Pilot signal of the vertical amplifier. Level about 8 Vpp.

TP2F - Super Sand Castle (SSC), generated from the DEFLECTION stage for the CHROMA stage. Level about 5 Vpp.

TP3F - VKOIN. Coincidence signal. It starts when a TV signal is recognized.

TP4F - Vertical synchronisms impulses, with frequency 25 Hz, 3Vpp, produced by

the microprocessor only when yhe teletext is in use. These impulses are used for the syncronization of the vertical amplifier

TP5F - Feedback signal of the vertical yoke used to check the amplitude of the image. Level: 4 Vpp with background 12V DC.

TPIG - Vertical deflection ramp signal. Level: 1.5 Vpp.

TP2G - Input pulses to the horizontal EAT/DEFLECTION stage. TP1H - Square waves of level ab TP3H - Red, green, blue signal components towards the colour amplifiers.That

look like video signals without synchronism. Amplitude aVpp.TP1L - Not amplified .

42


LAB SESSION 09

OBJECT: -

TO SIMULATE FAULTS (1).

Fault Simulation:-

Argument: REMOTE CONTROL:-

A normally open contact in a fault simulator closes at ground the input line P3.2 of the microcontroller 1C850 and it inhibits the remote control signals to arrive at the microcontroller, therefore all the remote control drives are inefficacious. The fault is elementary and it can be easily resolved even by a student who is at the beginning in locating faults. The purpose is to make the student analyse and understand which are the areas of the TV system touching the reception, the transfer and the carrying out of the drives coming from the remote control. The receiver of the signals IR emitted by the remote control is IC810, that includes a low noise amplifier in addition to the receiver IR. IC810 supplied by the line +H through the filter CR811/C81 I that removes the noise and transmits to pin 3 a square wave output containing the coded information that will be analysed by the microcontroller. When the remote control does not operate, the TP I A measured level is a high logic level. Once the pupil has discovered a TP 1 A wrong logic level constantly low, he will have to go on by examining the possible causes, such as: • IC810 faulty, with the input blocked at low level.

• CR811 interrupted and therefore not able to supply 1C810.

• CC 805 short-circuited. • CR817 interrupted. This is a pull-up resistor (IC811 has an open collector

output).

• CR803 interrupted. Another possible cause is a fault on the input circuit of IC850. It seems however less probable because a fault at circuits VLSI would compromise a greater number of functions and not a single door, while, in our case, only the control RC does not operate. Argument: KEYBOARD OPERATION:- A normally open contact of the fault simulator closes and put a grounded short-circuit on the input line on the pin 32 of IC850, microcontroller. This line (P2.2) is an input that the microcontroller uses to read the logic state of the keyboard. If this line is constantly low, the microcontroller does not detect any imput. The keyboard does not operate. The fault is elementary, but it leads the student to analyse and to understand the mechanism which the TV keyboard is analysed and interpreted by the microcontroller with. Once the pupil has localized, through the symptoms analysis, the interested area. The following possible causes can be considered:

43


• CR807 interrupted.

• CC807 short-circuited. • PU 1 keyboard common line

interrupted.

• 1C813 faulty.

Argument: MICROCONTROLLER:- A normally open contact in a fault simulator closes at ground the control pin of the regulator 1C676. The integrated is used as switch of ON/standby of the TV set. As a consequence the equipment goes in standby and it remains off. The purpose of the simulated fault is to make the student discover which parts of the system are interested in this function and to observe which sectors are constantly supplied, in standby state too. As possible fault sources, the following components will have to be:

• CC674 short-circuited. • 1C676 faulty.

• C863 short-circuited. •

• CT826 emitter-collector

short-circuited.

• CD830 interrupted..

• CR833 faulty.

Argument: MICROCONTROLLER RESET:-

A normally open contact of the fault simulator by operating short-circuits the input of the microcontroller Reset. This input is kept low by IC820 for some instants after the switching on to guarantee the stabilsation ofthe supply voltages and to exhaust the transitory states before the microcontroller starts operating.

A short-circuit on the Reset line prevents the microcontroller to operate and

therefore the TVC is off.

44


We expect that the student connects the symptoms of non-operation with the lack of operation of the microcontroller. He could initially suspect of IC850. Once the wrong logic level at TP4A has been located, we can obtain the following conclusions as possible causes: • CC826 faulty and with low level permanent output.

• 1C820 short-circuited and with reset kept constantly low.

• C827 short-circuited and with reset kept constantly low.

• Cc827 faulty.

• CR827 faulty.

45


Argument:-IMAGE CONTROL:- A normally open contact of the fault simulator closes and grounds CC848. The latter is a bias resistor on the line that provides the control voltage of the brightness of the RVB state. This voltage is a variable DC level, generated by the CPU. A ground short-circuit on the brightness control means that the image appears very dark, quite absent. The purpose of this simulated fault is to make the student do researches relative to the image control in the areas where it is processed (RVB stage) and where the control signals (microcontrollers) are generated. Once the symptoms have been examined, the student could initially think to a lack of the video signal coming from the RVB or IF stages (however, with the right synchronism signals, since the screen, even if dark, is steady). Once the research area is restricted at the single RVB stage, it is probable that the student does not think at once at the image control. Once he arrives there, however, the solution is immediate: • CR848 could be interrupted. • CR846 interrupted. • CR836 interrupted.

• C152 short-circuited. Argument: SERIAL BUS I T : -

A normally open contact of the fault simulator closes at ground, when it is run, the path of the signal SDA of the CPU at the semi-permanent memory (IC830). The SCL (Serial Clock Line) and SDA (Serial Data Line) are the two lines ofthe bus PC that allow the CPU to check different devices inside the system, the tuner included. The purpose of this fault is to induce the student to consider in detail the functions of the CPU and the characteristics of the serial bus. The student will easily realize that the lack of received signals does not depend on the tuner, but, since it is not easily accessible for the inspection, so as it is not in the TV sets, he will have to exert his ability of diagram analysis to lead more deep researches about the fault. The components that could cause the same symptoms are:

• CR869 open. • CC869 short-circuited. • 1C830 faulty

46


47

LAB SESSION 10

OBJECT:- TO SIMULATE FAULTS (2).

FAULT SIMULATION:-

Argument: TUNER:- A normally open contact of the fault simulator closes at ground the pin 3 of the tuner. Since this signal is one of the three activators for the band selection, the relative band (UHF) will not be able to be selected (TP3B remains low). The purpose of this fault is to make the student examine how the passage from a band to the other inside the tuner happens according to the controls coming from the CPU system. The student will pay attention to the tuner only after a look to the symptoms, since the operation is normal in VHF and faulty in UHF. The circuit analysis and their understanding will exert the student’s ability. The components that can be accepted as faults, since they cause the same effects

are:

• UV 1315 faulty.

• CT845 faulty.

• CC2845 short-circuited. • CC2841 short-circuited. • CR2841 faulty.





• CT2840 faulty in junction C - E.


Argument: DEMAGNETIZATION CIRCUIT:- A normally open contact of a relay of the fault simulator, if closed, puts a ground on pin 41 of IC850. This pin carries a control logic level whose contact closes the demagnetization coil on the AC supply. The purpose of this simulated fault is to accustom the student to work on diagrams and to research the circuit sections appointed to this specific function. Since the symptoms of the fault are not very striking, the student could even not realize that there is something irregular. It is therefore necessary that the teacher calls the student’s attention to the characteristic sound (sizzling) of the demagnetizer that operates when the TV is switched on with the relay push-button.


To locate the circuit section interested by the fault, the student will have to notice the following things: this TVC can operate with battery (12 V), even if this performance is not used in the trainer version. The 12 V power supply present but not used, contains the driver CT60072, the relay E2RE001 and the other components appointed to the control function of the demagnetizer.

The components that, being failed could generate this fault are:

• ERE l faulty relay.

• CR6071 interrupted. • CT6072 faulty. • CR879 faulty. The relay contact is rejected as cause, since it is possible to see at once that E 2 0 0 1 is not operating. The coil winding is not imputable too, since a measurement made on the collector of CT60072 shows that it is not at zero voltage. The components CD654, C656, CD656, and CR656 delay the rise of the pulse start duration (soft start). The adjustment control R654 is used to set the secondary voltages by regulating the +A voltage at minimum brightness and contrast.

Argument: IF STAGE:- A normally open contact of a relay of the fault simulator closes and grounds the circuit coming from pin 4 of IC150. This IC processes, according to the different standard (PAL, SECAM), the video information and sends to 1C850 a logic level UKON to signal that the received signal is recognized as a TV signal. If such a signal lacks, the CPU drives the audio and video muting (blue screen).

The components that can be considered valid as right answer are:


• CC866 short-circuited. Argument: HORIZONTAL DEFLECTION STAGE:-

A normally open contact of the fault simulator closes and grounds through a resistance the pin 39 of IC150. The altered signal interests the complex feedback network of the horizontal output stage, whose function is to report to pin 42 of IC 150, part of the signal going out from pin 5 of IC400 that supplies the coil V. The complexity of the feedback network has the purpose of assuring a uniform scanning of the screen CRT, necessary to build a right image. This simulated fault has a double purpose: first of all present the student a quite frequent default in TVC (even if effectively less frequent in the most recent models as regards the previous ones), making it therefore reflect on the symptoms relative to a specific part of the system. The second one is to carry the student to analyse the operation of the horizontal deflection stage.

48


The component acceptable as result of the research procedure and of the analysis of

the faulty part is:

• CC 166 low isolation.

• IC 150 faulty.

Other causes are more or less acceptable (but the fault blanking and the automatic reset of the trainer are not necessary) such as R426 heavily altered in value (improbable since it is a strong coiled resistor of IQ) C417 even less probable because one of its faults would overload IC400 with consequent disappearance of the image in case of bad operation, etc. ARGUMENT: RVB STAGE:-

A normally open contact of the fault simulator is closed and blocks the path of the signal that goes out from the pin 18 of IC 150 in the stage RVB. This pin carries the signal of the colour component B that goes out from the stage towards the final amplifier of the colour that is on the board CRT. The results that follows is an image with strongly altered colours (the blue component lacks). The purpose of this simulated fault is to familiarize the student with the aspect of an image when a colour component lacks and to try to connect this observation with the function of the interested system part. The conclusions acceptable for the research procedure are: in the RVB stage • CR153 interrupted. • T781 faulty. ARGUMENT: AUDIO AMPLIFIER:- A normally open contact of the fault simulator, if closed short-circuits CR321 towards ground. The amplifier receives the demodulated audio from the IF stage, signal available at pin 50 of IC 150. The audio waveform can be examined at TP 1 L and TP2L on the front panel of the trainer. The signal passes from CR321, CC321 and arrives at the not inverting input of IC320. The purpose of this simulated fault is to make the student analyse the operation of the audio section. The student begins with monitoring the signal at TP2L and this allows him to reject at once the possibility of a faulty loudspeaker. The components whose breaking can generate such symptoms and that are therefore acceptable as result of the research are: • CR321 faulty.

• CC322 faulty. • IC320 faulty.

49

TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering ARGUMENT: IF STAGE (AGC):- A normally open contact of the fault simulator closes to ground the pin 1 of the Tuner. On pin 1 a voltage generated by the stage IF of IC 150 is applied that controls the internal gain of the tuner. In the lack of the AGC voltage the gain of UV 1315 carried to the minimum therefore the audio and video signals are weak and very noisy. The components that can be considered valid as right answers: A1315 faulty. CR307 interrupted.

ARGUMENT: AV SWITCHING:- A normally open contact of the fault simulator closes to ground the pin 16 of 1C 150 disabling the control of AV generated from the CPU when selected by the remote control. The result that the TV does not go in AV and it always remains the signal received from the antenna. The TP 1 C signal is irregular. The components that can be considered valid as right answer are:

• CR974 faulty. • CT840 interrupted . ARGUMENT: RVB STAGE:- A normally open contact of the fault simulator, when activated short-circuits at ground the path from pin 11 of CIC 105 at pin 29 of IC 150 in the RVB stage. The signal R-Y cannot therefore pass the delay stage. The TP2D signal is irregular.

Find this fault demands measurements and controls that will have to be carried out on the Chroma circuit and therefore it can be consider as a difficult test, even if the fault simulation is immediately available. The components that can be considered valid as right answer for the removal of the fault are: • CIC 105 faulty.

• CR175 interrupted. • CC 126 interrupted. Argument: VERTICAL DEFLECTION STAGE:- A normally open contact of the fault simulator closes and grounds CC 157. This component is part of a complex feedback network of the vertical output stage, whose function is to report at pin 44 of IC 150, part of the signal coning out from pin 5 of IC400 and that supplies the coil V. The complexity of the feedback network has the purpose of assuring a uniform scanning of the screen CRT, necessary to build a right image. This simulated fault has a double purpose: first of Al present the student a quite frequent default in TVC (even if effectively less frequent in the most recent models as regards the previous ones), making it therefore reflect on the symptoms relative to a specific part of the system. The second one is to carry the student to analyse the operation of the horizontal deflection stage.

50

TV & Radar Systems . NED University of Engineering & Technology – Department of Electronic Engineering The signal at TP1 G pin appears faulty. The bad operation symptoms coming from this simulated fault can appear different according to the adjustment of the medium beam. In certain cases the screen appears dark and with a horizontal white line, in other ones the screen appears completely dark. The component acceptable as result of the research procedure and of the analysis of

the faulty part is:

• CC157 faulty. • RR411 faulty.

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TV & RADAR SYSTEMS (TC-335)

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