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TV PATTERN GENERATOR
GV-298
1 GENERAL
1.1 Description
The exceptional attributes the GV-298 video generator consists of have been
designed in accordance with the latest trends of modern technology.
Its application field is ranging to every use in which a professional feature is
requested, such as to achieve the hardest requirements both in the synchronism step,
and the colour and radiofrequency ones.
User-friendly, compact and strong, the GV-298 is a specified tool for all
servicing needs. The GV-298 will become a consummate partner for after-service
professionals, both in workshop tasks and home repairs and fittings.
Eight different pattern charts are available, allowing essential settings to be
made in any television receiver, as well as to detect abnormalities through a visual
picture examination. Besides, these equipment builts in four additional functions, to be
connected or disconneted at will in every chart. This monitoring affects picture
interlacing, chroma subcarrier, sound and PAL commutation.
The synthesized RF modulator ranges from 37 MHz to 865 MHz, so any defect
in tuning circuits or in the IF of the receiver can be detected. Tuning is performed by
channel (CCIR, OIRT or FCC channes, depending on versi on), or directly by frequency
in 50 kHz steps. A two-cell attenuator allows up to a maximum of 60 dB to be
attenuated in 20 dB steps.
A microcontroller carries out the interaction with the user, by displaying chart,
channel and frequency (5-digits) at any time, on a 16-character display . Data displayed
may be changed in an easy way by means of three pushbuttons.
In order to increase quality and reliability of the GV-298, the built-in
microprocessor carries out a checking of several equipment devices during its
connection and use.
An Euroconnector is included, as well as an oscilloscope synchronizing output.
This equipment is i nt ended for c overi ng B, G and H st andards (CCIR). Versi ons
are available too for I, DK and N systems.
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1.2 Specifications
TV SYSTEM
System
RF sta ndard
Line freque ncy
Frame frequency
H orizonta l synchronism
Line pe riod
Pre vious pede stal
Synchronism
Blanking
Ve rtica l synchronism
Frame period
Blanking
Pulse time of:
- P re - e qua liz in g
- E qua liz ing
- P ost- e qu a liz ing
Frame sweep
Colour subcarrie r
Subca rrier freque ncy
Burst duration
Bur st pos ition
Phase
CCIR PAL
B, G, H (DK, I, N on request)
15625 Hz
50 Hz
64 µs ± 0.0002 µs
1.5 µs ± 0.3 µs
4.7 µs ± 0.2 µs
12 µs ± 0.3 µs
20 ms
25 H + 12 µs (H = 64 µs)
2.5 H
2.5 H
2.5 H
Selectable: - 2:1 interlaced ratio
- No interlaced
F=4.3361875 MHz <±30 ppm PAL B,G,H, DK,I.
F=3.582056 MHz <± 30 ppm PAL N
(10 ºC to 40 ºC).
2.5 µs (10 ± 1 F period)
At 5.6 µs from the line previous synchronism
flank.
135º as referred to U axis at the following
sequence:
Line Frame
1 2 3 4
Even - - + +
Odd + + - -
Amplitude error
Phase error
Subca rrier a mplitude
Re sidual subca rrier
± 5%
± 3º
ON/OFF , selectable
3% (as related with red colour amplitude, 100%
saturated).
DISPLAY
Digital, 16 characters, 5-digit frequency display,
channel, TV standard, programme, pattern chart
and sound system.
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TEST PICTURES
P atte rn cha rts a va ila ble
8
1.- 100% white pattern
2.- Electronic circle grid
3.- Dots
4.- Checkboard
5.- Colour bars
6.- Red pattern
7.- Green pattern
8.- Blue pattern
Anti-PAL pattern by removing the R-Y switching
RADIOFREQUENCY OUTPUT
Range
Tuning
From 37 to 865 MHz (synthesized)
By frequency: in 50 kHz steps
By channel: CCIR (OIRT version /2, FCC
version /6).
Output a mplitude
Attenuator
Output impe dance
Connector
80 dBµV ± 3.5 dB
0-60 dB in 20 dB steps
75
Ω
BNC
STABILITY
At constant tempe rature
At temperature
FREQUENCY INDICATOR
Indicator
Resolution
VIDEO MODULATION
M odulation type
M odulation index
Vide o/sound ra tio
SOUND MODULATION
Ca rrier fre quency
M odulation type
Drift
MODULATION SIGNAL
Inte rnal
Frequency
COMPOSITE VIDEO SIGNAL
Amplitude
Bias
Output impe dance
Connector
<1.2 x 10-3 /10 min. (the first 15 min.)
<4 x 10-4 /10 min. (during the first hour)
<1 x 10-4 /ºC (5 to 40 ºC)
In the 5-digit LCD display
50 kHz
AM, double side band
~ 85%
13 dB
5.5 MHz, ON/OFF selectable
FM
30 kHz
1 kHz ± 10%
1 Vpp
Positive
75
Ω
BNC and EUROCONNECT OR
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R-G-B OUTPUTS
Amplitude
Output impe dance
Connector
TRIGGER OUTPUT FOR OSCILLOSCOPE
Signal
Amplitude
0.7 Vpp
75
Ω
EUROCONNECTOR
Vertical + Horizontal
2 Vpp vertical
1.5 Vpp horizontal
5 k
Output impe dance
Connector
LOW FREQUENCY OUTPUT
Amplitude
Frequency
Output impe dance
Connector
POWER SUPPLY
M ains volta ge
Consumption
Ω
BNC
250 mVpp
1 kHz
10 k
Ω
EUROCONNECTOR
110-125-220-230/240 V AC ± 10%/50-60 Hz
8 W
OPERATING ENVIRONMENT CONDITIONS
M a x. a ltitude
Temperature range
M a x. re la tive h um idity
2000 m
From 5 ºC to 40 ºC
80% (up to 31 ºC), decreasing lineally up to 50%
at 40 ºC.
PHYSICAL FEATURES
Dimensions
Weight
ACCESSORIES INCLUDED
90901207 BNC/TV coaxial cable, CC-07
90901105 Mains cable, CA-05
Spare fuse, 5 x 20 mm, 250mA, F, 250V
VERSIONS
GV-298
GV-298/2
GV-298/4
GV-298/6
PAL B, G, H. CCIR channels
PAL DK. OIRT channels
PAL I. CCIR channels
PAL N. FCC channels
W.102 x H.90 x D.241 mm
2.250 kg
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2 SAFETY RULES
* This is a
corresponding
* Use this equipment only with
connecte d at ground potentia l or insulated from the ma ins
* This equipment can be used in
environments
* When using some of the following accessories
equipment, for safety reasons plug it to a supply line with the
class I
ground terminal
.
systems or devices with the negative measuring
.
Ca tegory II Instalations
and
Pollution Degree 1
.
use only the specified ones
ensure safety.
Power cord
* Observe all
specified ratings
both of supply and measurement
* Remember that voltages higher than 60V DC or 30V AC rms are dangerous
* Use this instrument under the
*
The use r is only authorize d to
specified e nvironmental conditions
carry out the following maintenance operations:
Replace the mains fuse of the specified type and value
to
On the Maintenance paragraph the proper instructions are given. Any other
change on the equipment should ve carried out by qualified personnel.
*
The me a suring negative
* Follow the
clea ning instructions
is at ground potential.
described in the Maintenance paragraph
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* Symbols related with safety:
DIRECT CURRENT
ALTERNATING CURRENT
DIRECT AND ALTERNATING
GROUND TERMINAL
PROTECTIVE CONDUCTOR
FRAME TERMINAL
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EQUIPOTENTIALLITY
ON (Supply)
OFF (Supply)
DOUBLE INSULATION PROTECTED
(Class II Protection)
CAUTION
(Risk of electric shock)
CAUTION REFER TO ACCOMPANYING DOCUMENTS
FUSE
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3 I N ST ALLAT IO N
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3. 1 P owe r re quirem en ts
This equipment requires a mains power source of 110-125-220 or 230/240 V
AC 50 to 60 Hz. Mains operating voltage can be selected at the rear panel.
Figure 1.-
Pull out the fuseholder lid.
1.-
Set the proper fuse for the desired mains voltage.
2.-
Insert the fuseholder lid so the
3.-
display
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[ B ]
.
Selection of mains voltage.
pointer faces the desired mains voltage
[ A ]
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CAUTION:
THE EQUIPMENT IS FACTORY SET FOR 220 V OPERATING VOLTAGE.
BEFORE SWITCHING ON THIS INSTRUMENT, SET THE VOLTAGE
SELECTOR TO THE PROPER POSITION AND BE SURE THAT THE FUSE
VALUE IS CORRECT.
FUSE TYPE SHOULD BE: 5 x 20 mm., 250 V, F, and:
250 mA FOR ALL VOLTAGES
AVOIDING THIS DIRECTIONS COULD DAMAGE THE EQUIPMENT
3.2 Installation
This unit is ready to be used as a desk-top equipment.
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4 OPERATING INSTRUCTIONS
4. 1 D e scription of controls
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Figure 2.-
[1]
[2]
[3]
[4]
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. Mains switch.
LINE
LCD disp lay
In the e vent of a malfu nction , this pa rt will dis play an error code.
This area is designed for chart displaying. The several charts are
PAT.
specified by a letter, as drawn on the front panel.
Chart selection LED indicator. When this LED is on, the selected chart can be
changed by pressing key [12] (increase) or [13] (decrease).
. This display shows pattern c hart selec ted, channel and frequency.
Front panel.
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[5]
[6]
[7]
[8]
[9]
[10]
CHAN.
selected frequency does not belong to any channel as implemented in the
equipment, this area is blank. TV channels are designated with a "C" and a
number; for instance, channel 41 is "C41". Cable TV channels are designated
with an "S"; say "S11". (Implemented channels depend on version chosen).
Channel selection LED indicator. When this LED is on, the selected channel
can be changed by pressing key [12] (increase) or [13] (decrease).
FREQ. MHz.
displayed with 5 digits, two of which are decimals.
Frequency selection LED indicator. When this LED is on, frequency tuned can
be changed by pressing key [12] (increase) or [13] (decrease), in
steps of 50.
-----4 0 dB a ttenua ting cell
in the radiofrequency output RF 75Ω [11].
-----2 0 dB a ttenua ting cell
in the radiofrequency output RF 75Ω [11].
Display area designed for showing that channel tuned. When the
Display area designed for showing frequency. Frequency is
. On pressing this key, a -----40 dB attenuation is entered
. On pressing this key, a -----20 dB attenuation is entered
[11]
[12]
[13]
[14]
[15]
[16]
RF 75Ω
modulates the radiofrequency (RF) carrier in negative amplitude and at double
side band. Impedance is 75 Ω.
Incre a sing key
display [2].
Decreasing key
display [2].
. Selection key to select the display active area [2]. Upon selecting the
SEL
active area, the displayed current information can be changed by pressing key
[12] (increase) or [13] (decrease).
SOUND
sound subcarrier comes out, frequency-modulated by a 1 kHz signal.
NOTE:
Low frequency signal in pins 1-3 of the EURO- A V [2 1] Euroconnector is unable
to be removed, because the SOUND key [15] acts on the carrier only.
INTE RLACED
. Modulated radiofrequency output. Composite video signal
. The next information is shown in the active area of the
. The former information is shown in the active area of the
. This key enables the sound subcarrier. On pressing this key, the
. On pressing this key, the interlacing is removed.
[17]
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. PAL switching suppression key. On pressing this key, that typical PAL
PAL
system R-Y signal is removed.
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[18]
[19]
CHROMA
VIDEO 75 Ω 1 V pp
positive bias. Output impedance is 75 Ω.
. Colour subcarrier suppression key, to remove col our subcarrier ful ly.
. Composite video output with 1 Vpp amplitude and
Figure 3.-
[20]
[21]
[22]
4.2 Start-up
switched to mains and started up by pressing the
09/96 GV-298
Mains input set
EURO-AV
TRIG .S COP E
Once mains voltage to be used has been selected (point 3.1), the unit can be
. Euroconnector
. Com posite signal output for trigger oscilloscope
Rear panel.
LINE
switch [1].
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4.3 Using the equipment
This section explains how to use the GV-298, including keyboard operation,
composite video signal, radiofrequency, error messages; information appearing on the
display is detailed as well.
4.3.1 Display and keyboard
Figure 4
Depending on information shown, the display [2] may be divided in three areas.
The first area
[3] displays that pattern currently operating. Value shown
PAT.
in this area is any one of those letters specifying the pattern charts, as drawn on the
GV-298 front panel.
The second area
CHAN.
[5] displays the channel tuned. If a selected frequency
does not belong to any channel implemented in the equipment, this area is blank.
Otherwise, the number of the channel tuned is displayed.
Finally, the third area
FREQ. MHz.
[7] is designed to display the tuned
frequency (in MHz), with 5 digits, two of which are decimals.
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A LED is provided just under each of these three areas described. Function of
key
[14] is to enable one among these LED every time it is pressed. In this way,
SEL
by pressing it recurrently, LED are lighted on sequentially.
The enabled LED shows which display area is active, i.e., the current
information can be changed by pressing key [12] (increase) or [13]
(decrease).
4.3.2 Output signal
In using the GV-298, two different ways may be discerned;
Use of the composite video signal
a.
Use of the radiofrequency (RF) stage
b.
All parameters adjusted for the composite video signal are valid for the
modulated RF signal.
Current R, G and B signals in the
EURO-AV
Euroconnector [21] have fixed
amplitude. These outputs cannot be used for analyzing the Anti-PAL signal, since it is
a natural characteristic of this signal that it affects the colour subcarrier.
CAUTION
To achieve a right operation of the GV-298 when an output is connected to a n
external unit, make sure impedances are suited correctly as specified in
point 1.2 . O the rwise, a wrong ope ration could be noticed.
4.3.3 Pattern selection
To select a pattern, the
enabled. To this end, press key
[4] chart selection indicator LED should be
PAT.
[14] sequentially. Next to, that letter suiting with
SEL
the required chart will be displaye d, by pres sing pushbuttons [12] (increase) or
[13] (decrease).
4.3.4 Test pictures application
Patterns are assembled in two rows, showing affinity in use.
-Top row:
including four patterns intended for adjusting B/W parameters.
A.- 100% white scr een:
Checkup of the beam current li mi ter c i rcui t . Vi deo
recorders modulation adjustment and signal-to-noise ratio
measurements.
B.- Circle grid:
Adjustment of static and dynamic convergency. Interl aci ng
checkup. Adjustment of aspect ratio and picture centering in the
screen. Adjustment of picture geometry and linearity through the
electronic circle.
C.- Dots:
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Focus voltage adjustment.
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D.- Checkboard:
Video amplifier response analysis at low frequencies.
A white level pulse is yield by all pattern charts, just before the previous sweep
pedestal. This component all ows video s ignal s to be s urveyed through t he osc illoscope,
as the line change is displayed just at the time it arises. This pulse cannot be seen in
a conventional receiver, for it is hidden behind the right side of the screen.
- Bottom row:
E.- 100% white bars:
F.- Red screen:
G.- Green screen:
including four patterns intended for adjusting the colour stage.
Checkup of colour matrix, saturation, etc.
Purity control of red colour (R), noise and beam current.
Purity control of green colour (G), noise and beam
current.
H.- Blue screen:
Purity control of blue colour (B), noise and beam
current.
4.3.5 Function keys
Keys [15] to [18] allow some pattern capability to be extended in order to
enlarge their application field. Specification of these additional functions follows:
[15] SOUND:
This key enables the sound subcarrier. On pressing it, the
sound subcarrier is frequency modulated by a 1 kHz signal. This
subcarrier frequency varies depending on which system the GV-298 has
been fitted for: 5.5 MHz for PAL B, G and H (GV-298 ground version),
6 MHz for PAL I (GV-298/4 version), 6.5 MHz for PAL DK (GV-298/2
version) and 4.5 MHz for PAL N (GV-298/6 version).
NOTE:
Low freque ncy signal in pins 1-3 of the E UR O- AV [2 1 ] E uroconnector is
unable to be removed, because the SOUND key [15] acts on the carrier
only.
[16] INTERLACED:
Interlacing cancellation. This function is useful when
adjusting convergencies. In the grid pattern, horizontal lines are shaped
by two white lines; one from the even frame, the other from the odd one.
If this pattern is watched from a close position to the screen, flickering
is very pronounced. Thence, user would have it easier to remove
interlacing; i n thi s way, that f l i ckeri ng i s removed too. Besi des, i nt erl aci ng
suppression allows the vertical integration system of the synchronism
separator to be verified.
[17] PAL:
In a standard operation of a colour patt ern, the GV-298 will transmit
component +(R-Y) and +(B-Y) in one line, and component -(R-Y) and
+(B-Y) in the next line; i.e., signal (R-Y) is switched in each line, but
component (B-Y) is kept constant. This process concerns both chroma
vectors and burst, which is eventually telling the receiver how to switch
the (R-Y) signal sensed, in order to retrieve the source colour signal.
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On pressing key
, (R-Y) switching -PAL system typical- is
PAL
suppressed. Anyhow, as the burst switching is kept, the receiver will
perform the (R-Y) switching further. As a result, no signal at all will come
out at the (R-Y) demodulator output if the receiver is adjusted correctly.
On a properly adjusted TV set, lack of (R-Y) component can be
observed in the colour bar signal picture without PAL switching.
[18] CHROMA:
The colour subcarrier may be suppressed fully. In this way,
luminance can be analyzed in colour patterns.
Lack of chroma in the transmitted signal shall enable the colour killer
circuit of the receiver. Therefore, if a screen colouring appears in such
conditions, it should be charged to a defective working in some stage or,
in some cases, to a excess o f gain of chroma amp lifiers.
4. 3. 6 Ra diofreque ncy stage
Radiofrequency (RF) carrier is modulated by the composite video signal, in
negative amplitude and double side band. This signal is available at the RF
connector output [11]. Im pedance is 75 Ω.
Frequencies selected by the user are programmed into the RF unit by a
microprocessor. Frequency tuned is displayed at any time. Tuning is performed in two
ways, whether by
channel
, or by
frequency
directly.
4. 3. 6 .1 T uning by channel
The GV-298 pattern generator is carrying out a great number of standard
channels, easy to access through the keyboard. On pressing key SEL [14] repeatedly,
the CHAN [6] LED indicator will light on. In this condition, the display shows "C?"
(channel may be changed). Increasing [12] key or decreasing key [13] are
used for channel varying. The selected channel will then be displayed, together with
its frequency.
The following table lists both channels, frequency ranges and TV bands
assigned. (Ground version, CCIR channels).
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Band Fre que ncy range Cha nne ls
I F 38.9 MHz IF
I B 47 - 65 MHz 2 - 4
MIDDLE 104 - 174 MHz S1 - S10
B III 174 - 230 MHz 5 - 12
SUPER 230 - 300 MHz S11 - S20
HYPER 302 - 468 MHz S21 - S41
B IV 470 - 606 MHz 21 - 37
B V 606 - 854 MHz 38 - 69
NOTE:
"S " channels a re use d for cable T V signals transmission.
4. 3. 6 .2 T uning by frequency
Within the frequency range of the equipment (37 MHz to 865 MHz), any
frequency may be tuned in 50 kHz steps. In this way, any tuning may be approached,
even if it does not belong to any specified channel.
On pressing key
[14] sequentially, the
SEL
FREQ. MHz
[8] indicator LED will
light on. Next to, frequency to be tuned can be modified by using keys [12]
(increase) or [13] (decrease). When the tuned frequency matches a channel, the
display will read the number and type of that channel. In the event that tuned
frequency does not match any channel as specified by the equipment, no indication will
be displayed.
Since the modulation system is using a double side band, two apparently right
tuning points can be found. This does not happen on tuning a TV station, as system
used is a partially suppressed lower side band. In order to decide which from the two
points is the right one, this suits with the higher frequency, if tuning is done with a TV
set. On the contrary, it suits with the lowest frequency, when tuning through the
generator.
4.3.6.3 RF signal attenuation
To check automatic gain control circuits of TV sets, a two-cell (one -----20 dB cell
and one -----40 dB cell) attenuator has been built in, in order to attenuate the RF output,
if required. Maximum total attenuation is -----60 dB, in -----20 dB steps.
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dB ATTENUATION CELLS ENABLED
00 None
20 20 key [10] pushed
40 40 key [9] pushed
60 20 + 40 keys [10] and [9] pushed
With a -----40 dB (300 µV) attenuation, a properly adjusted TV set usually shows
a snow effect picture.
4.3.6.4 Intermediate frequency
Intermediate frequency used in TV set s is 38.9 MHz. In the GV-298, this carrier
is achieved by selecting a channel (see 4.3.6.1), or a frequency (see 4.3.6.2).
Intermediate frequency tuning by channel requires moving towards that first expected
channel, just before C02. Then, the display will show "IF", together with frequency
related to.
This configuration allows a modulated signal to be supplied to the I.F. stage
input of the receiver. This signal may be used to check whether the noticed failure is
due to the tuner or to a later stage.
4.3.7 Error messages
The GV-298 builds in a microcontroller ready to detect a defective running of
some equipment devices. As soon as an abnormal behaviour is found, an error
message is displayed in the following format:
ERROR: XX
Where XX is that number designing the kind of failure arisen, for instance:
ERROR:00
An error message will vanish on pre ssing eithe r key [12 ], [13] or [14]. If er ror
persist s , t hat wa rning will appear again while the equipment is running. In such a case,
please contact your distributor, telling him the message shown by the GV-298.
Every time the GV-298 is connected, the unit performs an
to check its proper operation. If an error is sensed, the display will sh ow :
FAILED"
distributor should be contacted.
, which means some failure is arising. In this case, like formerly, your
AUTOTEST
in order
"AUTOTEST
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4. 3. 8 Output de scription
4. 3. 8 .1 C omposite video output
Positive composite video signal can be drawn through connector BNC,
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VIDEO
[19] on the front panel, w ith 1 Vpp amplitude and 75 Ω output impedance.
This signal is very useful for checking video monitors (B/W and color), line amplifiers,
VCR and any other equipment working with a composite video.
CAUTION
This signal should never be switched to voltage circuit points, but only on video
Ω
signal standa rdiz ed inputs with 75
ensuing from negle cting this ca ution are not covered by w arra nty.
4. 3. 8 .2 Euroconne ctor
(EN50049 DIN connector)
impeda nce. D ama ges a rise n in the unit
Generator GV-298 is provided with an EUROCONNECTOR type connector,
also known as SCART connector or PERITEL connector (according to NF-C92250
standard). Output signals from this connector are:
PIN NUMBER SIGN AL
1-3 1 kHz sound output
4 Sound ground
5 Blue ground (B)
7 Blue output (B)
8 +12 V switching output
9 Green ground (G)
11 Green output (G)
13 Red ground (R)
15 Red output (R)
17 Composite video ground
19 Composite video output
21 Connector shield ground
Figure 5.-
Description of EUROCONNECTOR switching pins
For more information, see point 1.2 (Specifications).
4 .3 . 8 . 3 T rig ge r os cillosc ope
When a TV set circuits are analyzed with the help on an oscilloscope,
desynchronization due to am plitude differences of signals watched is not desirable, as
is the case when synchronism is done internally. To get a quite synchronized picture,
regardless of signal amplitude, the external synchronism input of the oscillo s pe should
be used, connecting same to the TRIGG output of generator GV-298, connector
TRIG .S COP E
[22]. If the oscilloscope has, as all PROMAX types have, a TV
automatic filter connected to the time base switch, then passing from the horizontal
frequency to the vertical one can be made without synchronism loss. In this output,
horizontal pulses are mixed with higher amplitude vertical ones, thus providing the
oscillosc ope to be synchronized to vertical frequency.
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5 OPERATION PRINCIPLE
This chapter is an overview of the GV-298 operation. Explanation lies in block
diagram of Figure 6, at the end of this chapter.
5. 1 S ynchronism gene ra tor
The synchronism generator supplies two significant signals in order to allow
GV-298 output to be viewed through a TV set: these two signals are the horizontal and
the vertical synchronisms. The first one commands a line changing in the TV set while
the second one starts a screen sweep.
5. 2 C ontrol logic and colour genera tion
This module generates a video signal according to the pattern selected, the
function keys enabled and system chosen (PAL), giving rise to the three basic signals
(R, G and B). From them, luminance is issued (identified as "Y" in the block diagram).
R, G and B are carried to the colour module, which builds signals R-Y and B-Y.
These are used to square-modulate the colour subcarrier, which frequency is settled
by the system used .
Video signal is generated from luminance and chrominance, by a submodule
generator. This signal is carried through a stage in order to give a 75 Ω output
impedance to the video signal.
After crossing a suitable output stage, R, G and B signals are present in the
EUROCONNECTOR.
5. 3 S ound
The low frequency oscillator generates a 1 kHz signal used for sound
modulation. A carrier, frequency of which is specified by that standard used, is
frequency modulated by the low frequency signal and carried to the RF unit.
The 1 kHz signal is carried through an output stage, to fit it with a suitable
impedance; then this signal is switched to the EUROCONNECTOR.
5. 4 R a diofreque ncy unit
Function of the radiofrequency uni t i s to modulate bot h vi deo and sound si gnal s
with a user's selected frequency carrier. This unit is synthesized in order to ascertain
a minimum drift in that signal supplied by the GV-298.
An attenuation unit allows that level supplied by the RF unit to be varied in a
0 dB, 20 dB, 40 dB and 60 dB scale.
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5. 5 M icrocontroller
This component operates interaction between the GV-298 and the user,
directing the display and the keyboard. This microprocessor gives relevant commands
to the RF unit and to the control logic module, in order to generate a suitable signal to
user's requirements.
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6 MAINTENANCE
6.1 Replacing the mains fuse
The fuseholder lid is placed in the mains base (see figure 1) and it is the
voltage selector.
To substitute the fuse, disconect the power cord.
With an appropiate screw driver remove the fuseholder lid.
Substitute the melt fuse for another of:
FUSE TYPE SHOULD BE: 5 x 20 mm., 250 V, F, and:
250 mA FOR ALL VOLTAGES
AVOIDING THIS DIRECTIONS COULD DAMAGE THE EQUIPMENT
When inserting the fuseholder lid be careful that the voltage selector is in the
correct position according to the mains.
6. 2 C le aning re comme ndations
CAUTION
To cle an the cover, take care the instrument is disconnected
CAUTION
Do not use scented hydrocarbons or chlorized solvents. Such products may
a ttack the pla stics use d in th e c onstructio n of the cove r.
The cover should be cleaned by means of a light solution of detergent and
water applied with a soft cloth.
Dry thoroughly before using the system again.
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TABLE OF CONTENTS
1 GENERAL .................................................. 31
1.1 Description .............................................. 31
1.2 Specifications ............................................ 32
2 SAFETY RULES.............................................. 35
3 INSTALLATION .............................................. 37
3.1 Power requirements ........................................ 37
3.2 Installation ............................................... 38
4 OPERATING INSTRUCTIONS .................................... 39
4.1 Description of controls ...................................... 39
4.2 Start-up ................................................. 41
4.3 Using the equipment ....................................... 42
4.3.1 Display and keyboard ................................... 42
4.3.2 Output signal ......................................... 43
4.3.3 Pattern selection ...................................... 43
4.3.4 Test pictures application ................................. 43
4.3.5 Function keys......................................... 44
4.3.6 Radiofrequency stage ................................... 45
4.3.6.1 Tuning by channel .................................. 45
4.3.6.2 Tuning by frequency ................................ 46
4.3.6.3 RF signal attenuation ............................... 46
4.3.6.4 Intermediate frequency .............................. 47
4.3.7 Error messages ....................................... 47
4.3.8 Output description ..................................... 48
4.3.8.1 Composite video output .............................. 48
4.3.8.2 Euroconnector .................................... 48
4.3.8.3 Trigger oscilloscope ................................ 48
5 OPERATION PRINCIPLE ....................................... 49
5.1 Synchronism generator ..................................... 49
5.2 Control logic and colour generation ............................. 49
5.3 Sound .................................................. 49
5.4 Radiofrequency unit ........................................ 49
5.5 Microcontroller ............................................ 50
6 MAINTENANCE .............................................. 53
6.1 Replacing the mains fuse .................................... 53
6.2 Cleaning recommendations .................................. 53
09/96 GV-298
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