INSTRUCTION
MANUAL
Model 1249B
NTSC GENE RATO R
2
TEST INSTRUMENT SAFETY
Normal use of test equipment exp oses you to a certai n amount of danger from electrica l shock because t esting must someti mes be p erformed
where exposed voltage is present. An electrical shock causing 10 milliamps of current to pass through the heart will stop most human
heartbeats. Voltage as l ow as 35 volts dc or ac r ms should b e considered danger ous and hazardous si nce it can pr oduce a l ethal current under
certain conditions. Higher voltages pose an even greater threat because such voltage can more easily produce a lethal current. Your normal
work habits should include all accepted practices to prevent contact with exposed high voltage, and to steer current away from your heart in
case of accidental contact with a high voltage. You will significantly reduce the risk factor if you know and observe the following safety
precautions:
1. Connect the NTSC Generator’s ac power cord only to a 3-wire outlet to assure that the instrument’s chassis and ground leads or probes
ore test ca bles ar e at eart h ground.
2. Don't expose high voltage needlessl y to the equipment under test. Remove housings and covers only when necessar y. Turn off equipment
while making t est connect i ons in high-volta ge circuits . Disc harge high-voltage capacit ors after r emoving p ower.
3. If possible, familiarize yours elf with the equipment being tested a nd the location of its high volta ge points. However, remembe r t ha t hi g h
voltage may appear at unexpected points in defective equipment.
4. Use an insulated floor material or a large, insulated floor mat to stand on, and an insulated work surface on which to place equipment;
and make certain such surfaces are not damp or wet.
5. Use the time proven "one hand in the p ocket" technique whil e handling an instrument probe. Be partic ularly careful t o avoid contacting a
nearby metal object that could provide a good ground return path.
6. When testing video equip ment that i ncludes a pict ure tube or CRT, remember t hat the high volt age power supply and CRT anode operat e
at very high voltage, often 20,000 volts or more. Carefully void these areas when the equipment is operating. It is also typical for these
circuits to retain a high voltage charge long after the equipment is turned off. Before attempting any servicing with the power removed,
discharge hi gh voltage pints. Also avoid bumping the CRT with a sharp edge. Because of the high vacuum, a nick ed CRT may “implode”
and cause fl ying glass fragments.
(continued on inside rear cover)
WARNING
3
TABLE OF CONTENTS
Page
TEST INSTRUMENT SAFETY ............................. inside front cover
INTRODUCTION ........................................................................4
FEATURES .......................................................................................... 5
SPECIFICATIONS .............................................................................. 6
DEFINITIONS OF TERMS ................................................................ 8
THE NTSC COLOR VIDEO SIGNAL ............................................ 11
History ......................................................................................... 11
Horizontal Sync ........................................................................... 11
Vertical Sync ............................................................................... 12
Amplitude .................................................................................... 12
Color ............................................................................................ 15
NTSC Color Bars Signal ............................................................. 15
CONTROLS AND INDICATORS ................................................... 18
OPERATING INSTRUCTIONS ....................................................... 22
Precautions a nd Tips ................................................................... 22
Familiarization ............................................................................ 22
Initia l Set-Up ............................................................................... 22
NTSC Sta ndard Color Bar P atter n ............................................. 24
Staircas e Pattern .......................................................................... 25
Color Bars W ith 100 % White ..................................................... 25
Staircas e With 100% White ........................................................ 25
Convergence Patt er ns .................................................................. 25
Page
Black Rast er Patter n .......................................................... 25
4.5MHz Subcarri er Us e ........................................................... 25
RGB Output ............................................................................. 25
Wa ve for m M on it or in g ............................................................. 26
Simultaneous Outputs .............................................................. 27
APPLICATIONS .............................................................................. 28
NTSC Color Bars ..................................................................... 28
Staircase ................................................................................... 29
Convergence ............................................................................. 29
RF and I-F ................................................................................ 29
Sync .......................................................................................... 30
30Hz Output ............................................................................. 30
CCTV Applications ................................................................. 30
CATV Applications ................................................................. 30
MATV Applications ................................................................ 31
Vectorscope Meas urements .................................................... 31
MAINTENANCE ..................................................................... 34
Case Removal ......................................................................... 34
Fuse Replacement ................................................................... 34
Calibration ....................................................................... 34
SERVICE INSTRUCTIONS ...................................................... 38
LIMITED ONE- YEAR WARRANTY ....................................... 39
4
INTRODUCTION
T
he B+K PRECISION Model 1249B NTSC Generator is a
versatile, low cost, precision television/video signal
generator. It generates a variety of test signals and pat terns for
comprehensive testing, servicing, and adjustment of video and
television equipment. Its applications include television
receivers, video tape recorders, closed circuit television
systems and components, and master antenna systems and
components, as well as most standard computer and video
monitors.
The instrument can generate many different patterns, each of
which is available as a composite video signal or a modulated
rf output on c hannel 3, channel d, or the standard television i-f
frequency of 45.75MHz. This provides the proper signal for
inject ion at any poi nt in the equipment.
The video patterns include standard NTSC color bats with
standard 7 5% whit e or with 100 % white, staircas e, black raster,
and an assortment of convergence patterns. An engineer or
technicia n with a good knowledge of vi deo c irc uits can use t he
variety of patterns to analyze and isolate almost any video
problem.
The NTSC Color Bars signal generated by the instrument is
the same type of color bar signal that is used by the television
networks, al lowing
it to be used to set-up and adjustment TV sets and other
equipment for the best performance. This is not possible
with lower cost gated rainbow color generators, which
produce a si gnal unlik e that used dur ing nor mal op eration.
Separate RGB and sync outputs are available for use with
most computer and video monitors using standard 525 line.
15.750KHz scan. The inputs to these RGB monitors are
separate digital s ignals f or red, green, and bl ue, a nd separat e
digital composite sync or separate digital vertical and
horiz ontal sync. The s ignal level a t the RGB outputs is swit ch
selectable between TTL and low (0.8V). The D-type
subminiature connector is directly comparable with IBM
Model 5153 PC monitors (TTL signal level should be
selected f or use wit h the IBM PC monitor) .
Other features include a crystal generated 30Hz TTL output
and a switchable 4.5MHz sound sub-carver modulated with
a 1 kHz audio tone. The 30Hz signal is useful for isolating
servo problems in video cassette recor ders.
The switch selectable 4.5MHz sound sub-
carrier is
modulated by a 1KHz tone and is used to check the sound
circuits and a udio/ video is olation.
5
FEATURES
NTSC CO LOR BAR S
Generates standard NTSC color bars pattern (eight bars of
standard EIA colors) at NTSC prescribed luminance and
chrominance l evels a nd phase.
SELECTABLE COLOR
Color ca n be switched on or off.
CONVE RGENC E PATTERN S
Dots, crosshatch, center dot, and cent er cr oss patterns for
stati c and dynamic c onvergenc e.
BLAC K RASTE R
Provides sync and reference black for a cl ear bl emish-free
raster.
CRYSTAL OSCILLATORS
IF, CH 3, C H 4. 30Hz. and s ync generation are crystal-
contr olled f or frequenc y acc urac y and stabi lit y.
COMPOSITE VIDEO OUTPUT
Composit e video out put wit h variabl e 0 to ± 1V p-p amplitude
into s tandard 75Ω impedance. Calibrated 1V p-p with
negative sync.
RF OUTP UT
Standard 75Ω outp ut modula t ed by composit e video at
10mV rms on c hannel 3, c hannel 4, or 45.75MHz i-f.
SYNC PU LSE OUTPUT S
All outputs can be used simultaneously for maximum
flexibility. Permits more comple me ntar y testing or
multiple independent usage of instrument.
RGB OU TPUTS
Digi ta l r ed, green and blue (RGB) signals for comp uter a nd
video monit or s with s tandard 5 25 line, 15.750KHz scan. D-
Type sub-minia t ure connect or provides r ed, green, blue,
horizontal sync, a nd vert ical s ync signal s and is IBM Model
5153 PC monitor compa tib le. Outp ut level is switc h
select able bet ween TTL a nd LOW (0.8±0.2V).
30Hz OUTPU T
30Hz TTL output is usef ul for video r ecor der app licat ions.
4.5 MHz SOUND S UB-CARRIER
4.5MHz subcarr ier modula t ed with 1KHz audio tone can be
switc hed on t o check sound a nd verify pic t ure and sound
isolation.
6
SPECIFICATIONS
PATTERNS
NTSC Color Bars:
White (75% or I00%. switch selectable), yellow, cyan,
green, magenta, red, blue, black (7.5% set-up). Chroma is
switch selectable; COLOR OFF obtains stair case from
color bars (stair case white level is switch selectable at 75%
or 100%). Interlaced sca n.
Chroma Accuracy:
±5° and ±5 EEE units.
Raster:
Black.
Convergence:
Center dot, 7 x 11 dots , ce nt er c ross,7 x 11 crosshatch.
Selectabl e interlac ed or progr essive sca n.
RF OUTPUT
Channels:
CH3, CH4, IF.
Frequency:
61.25, 67.25, 45.75MHz ±0.008MHz.
Level:
10mV rms minimum int o 75 ohms.
Impedance:
75 ohms.
Stability:
50 ppm.
VIDEO OUTPUT
Polarity:
Negative and p ositive s ync a vailable.
Amplitude:
Variable 0 t o ±1V p-p i nto 75 ohms. Calibrat ed 1V p-p
ava i lab l e wi t h ne ga ti ve s ync .
Impedance:
75 ohms.
RGB OUTPUTS
BNC and D-Typ e S ub-Mi niature Connec tors.
Patterns:
Convergence a nd col or bars.
Levels:
TTL l evel and l ow level, (0.8 ±0.2V), s witch
selectable.
Impedance:
75 ohms.
7
SPECIFICATIONS (CONT.)
NOTE: Specifications and information are subject to change without notice. Please visit www.bkprecision.com for the most current product
information.
SOUND SUBCARRIER
4.5MHz ±0.2% modulated b y appr oximately 1KHz
audio tone, switch s electabl e.
SYNC OUTPUTS
Composite:
NTSC-
M TTL level: negative polarity sync:
interlaced scan for NTSC color bars, selectable
interlaced or 'progressive scan for convergence
patterns.
Horizontal:
TT L le vel ( p osit i ve p ola r it y s ync ).
Vertical:
TT L l eve l (pos it i ve p ola r it y syn c ).
Impedance:
75 ohms.
30 Hz OU TP U T
Level:
TTL level sq uar e wave.
Impedance:
75 ohms.
COLOR SUBCARRIER
NTSC s ignal: 3.579545MHz (± 50Hz ) (adapt able t o PAL-M).
MISCELLANEOUS
Power Requirements:
105 to 130 VAC, 60Hz. 8 Watts.
Operating Temperat ure:
0° t o +5 0°C .
Dimensi ons (H x W x D ):
3-3/8" x 10-3/8" x 11-
7/16" (8 .6 cm x 26.4 cm x 29.1 cm)
Weight:
2.8 lbs (1 .30 kg).
OPTIONAL ACCESSORIES
BNC-to-F Five Foot RG-59/U Cable
(part number 539-124-0-000).
BNC-to-BNC Five Foot RG-59/U Cabl e
(part number 539 -123-0-000).
8
DEFINITIONS OF TERMS
BARS Pattern. See “NTSC Color Bars”.
Back Porch. The portion of a composit e video signa l between
the tr aili ng edge of th e hori zontal sync puls e and th e end of t he
horizontal blanking pedestal. The color burst occurs during the
back porch interval.
Blanking Level. The level of the front and ba ck porc hes. Zero
IEEE units.
Burst. See "Color Burst".
CATV Cab le Television. Also used for Community Antenna
Television.
CCTV. Closed-circuit television.
Chroma or Chrominance. The col or inf ormat ion cont ai ned in
a video signal, consisting of hue (phase angle) and saturation
(amplitude) of the color subcamer.
Chroma Ampli tude. . Ampli tude of 3.58MHz color subcarrier.
Represents saturation.
Chroma Phas e Angle. P hase angle of 3.5 8MHz color
subcarrier. Repr esents hue.
Color Bars. See "NTSC C olor B ars".
Color B urs t. A few (8 to 10) cycles of 3.58MHz color subcarrier
which occur during the back porch interval. Color burst amplitude is
40 IEEE units and phase is 180°. The color oscillator of a color
television receiver is phase locked to the c olor b urst.
Color Subcarrier. The 3.58MHz signal which carves color
information. This signal is superimposed on the luminance level.
Amplitude of the color subcarrier represents saturation and phase
angle represents hue.
Composite Video Signal. The entire video signal consisting of
blanking pulses, sync pulses, color burst, and chrominance and
luminance information.
Duty C ycle. Per centage of cycle dur ing which pul se is work ing.
A squar e wave has a 50% duty cycl e. Horiz ontal sync pul ses have
about 8% duty cycle-about 5µs pulse width at 63.5µs pulse
repetition period.
EIA. Electronic Industries Association.
Equalizing Pulse. A portion of the vertical blanking interval
which i s made up of bl anking level a nd six pulses (8% duty cycl e
at -40 IEEE units) at one-half the width of horizontal sync pulses
and at twice the repetition rate. One equalizing pulse occurs
immediately before, and another immediately after, the vertical
sync pulse.
9
DEFINITION S OF TER MS (CONT.)
Field. One-half a television picture. One complete vertical scan
of the picture containing 262.5 lines. Two fields make up a
complete television picture (frame). The lines of Field 1 are
vertically interlac ed with Field 2 for 525 li nes of r esoluti on.
Frame. A complete television picture, consisting of two fields.
See "Field".
Front Porch. Blanking l evel puls e at end of l ine of horizontal
scan, b efore horizontal s ync p ulse.
Horizontal Blanking Pedestal. That portion of each line of
composite video signal which blanks the picture while the CRT
retrace returns to the left side of the screen. Consists of front
porch, horizontal sync pulse, and back porch.
Horizontal Resolution. Smallest increment of a television
picture that can be discerned in the horizontal plane. This
increment is dependent upon the video bandwidth and is
measured in frequency. Horizontal resolution of a high quality
monochr ome televis ion r ec eiver is 4. 2MHz.
Horizontal Sync Pulse. Pulse at -40 IEEE units which
synchronizes horizontal scan rate of television receiver to
composite video signal. Starts each line at same horizontal
position.
Hue. Distinction between c olors. Red, b l ue, green, yellow, etc.
are hues. White, black, and gr ey are not consider ed hues.
IFFE. Institute of Electrical and Electronic Engineers.
IEEE Unit. A standard 1-volt peak-to-peak composite video signal
is divided into 140 equal units, scaled from -40 to +100, which are
then called IEEE units. Luminance and chrominance amplitude are
measured in IEEE units. Sync pulses extend from 0 to -40 units.
Blanking level is 0. Picture information spans the +7.5 set-up level
(black) to + 1 00 (10 0% whit e) l evel s. Chr oma a mplitude is t he p eak-
to-peak amplitude of the color subcarrier, which rides on the
luminance level.
Interlace. Vertical offset between Field 1 and Field 2 that causes
lines of Field 1 t o fall b etw een the li nes of Field 2. Also s ee "Fi eld".
Luminance. The amount of light intensity perceived by the eye as
brightness. Luminance information is represented by the amplitude
of the c omposite video si gnal.
MATV. Master antenna television.
Monochrome. Black and white television signal. Contains sync
and luminanc e but no color b urst or c hroma.
NTSC. National Television Systems Committee. Established the
color television standards now in use in the U.S.A., and many other
nati ons of the world.
NTSC Color Bars. A pattern generated by the NTSC Generator,
consisting of eight equal width color bars. Colors are white (75%),
black (7.5% set-up level), 75% saturated pure colors red, green, and
blue, and 75% sat urated hues of yellow, cyan, a nd magenta (mixt ures
or two c olors in 1:1 rati o without thir d col or).
10
DEFINITION S OF TER MS (CONT.)
Resolution. See "Horiz ontal R esoluti on" and "V ertical
Resolution".
Saturation. Vi vidness of col or. Degree to which a c olor is
not diluted by white light. Highly saturated color is very
vivid. The same hue becomes a pastel shade when diluted
by white light. Saturation is represented by chroma
amplitude and is measured in IEEE units. The number of
IEEE units for fully saturated color vanes from hue to hue.
Set-up. The separati on bet ween blanking a nd black
reference l evels. This instr ument uses t he NTSC sta ndard
set-up level of 7.5 units.
Staircase. A pattern generated by the NTSC Generator.
consisting of equal width luminance steps decreasing in
amplitude. The staircase pattern is useful for checking
linearity of l umina nce.
Subcarrier. See “ Color Subcarri er”.
VCR. Video ca ss ette recor der.
VTR. Video tap e rec order. In t his manual. t he term " VTR"
includes r eel-to-reel and cass ette type.
Vertical Blanking Interval. That portion at the beginning
of each field of composite video signal which blanks the
picture while the CRT retrace returns to the top of the
screen. The equalizing pulses and vertical sync pulse are
generated wit hin this inter val.
Vertical Resolution. Smallest increment of a television
picture that can be discerned in the vertical plane. This
increment i s dep endent up on the n u mb er of li n es of s c a n p er
frame, and is measured in lines. In the U.S.A. and other
countries using NTSC systems, vertical resolution is 525
lines.
Vertical Sync Pulse. A portion of the vertical blanking
interval which is made up of blanking level and six pulses
(92% duty cycle at -40 [ FEE units) at twice the horizontal
sync pulse repetition rate. Synchronizes vertical scan of
television receiver to composite video signal. Starts each
frame at same vertical position (sequential fields are
offset line t o ac hieve int erlaced sca n).
11
THE NTSC COLOR VIDEO SIGNAL
HISTORY
In 1953, the NTSC (National Television Systems
Commit tee) es tab lished t he c olor t el evisi on sta ndar ds
now in use by the television broadcast industr y in the
United States and many other countries. It was, of course,
compatible with the monochrome (black and white) system that
previously existed. The makeup of a composite video signal is
dictated by NTSC specifications. These specifications include a
525-line interlaced scan, operating at a horizontal scan frequency of
15.734.26Hz and a vertical scan frequency of 59.94Hz. A
3.579545 MHz subcarri er contains the c olor informati on. The phase
angle of the subcarrier represents the hue: the amplitude of the
subcarrier represent s saturation.
HORIZONTAL SYNC
(Refer t o Fig. 1)
The "begi nning" of a li ne hor izonta l sca n occurs at the l ea ding edge
of the horizontal blanking pedestal. In a television receiver, the
horizontal bla nki ng pedestal s tarts as the electr on beam of the CR T
reaches the extreme right-hand edge of the screen (plus a little
oversca n in most cases ). The horizont al blanking p edestal prevents
illumination of the screen during retrace, that is, until the electron
beam deflection circ uits ar e reset to the l eft edge of t he screen and
ready to start another line of video display. The entire horizontal
blanki ng pedes ta l i s at the blanking level or the s ync puls e level. In
a television receiver, the blanking and sync pulse levels are the
"blacker than black" levels that assure no illumination during
retrace.
The horizontal blanking pedestal consists of three discrete parts:
the fr ont porch, t he horizontal sync puls e, and the back porch. T he
front porch is a 1.40 microsec ond period at sec ond
Fig. 1. Composite of Video Signal; One Horizontal
Line of NTSC Color Bars Signal
12
THE N TSC CO LOR VIDEO SIGNAL (CONT.)
horizontal sync pulse at the -40 IEEE units level. An explanation
of IEEE units follows in the "Amplitude" paragraph. When the
horizontal sync pulse is detected in a television receiver, it
initiates flyback, which ends the horizontal scan and rapidly
resets the horizontal deflection circuit for the next line of
horizontal scan. The horizontal sync pulse is followed by a 4.79
microsecond back porch at the blanking level. When a color
signal is being generated, 8 to 10 cycles of 3.579545MHz color
burst occur during the back porch. The color burst signal is at a
specific reference phase. In a color television receiver, the color
oscill ator is p hase locked to t he color b urst ref eren ce phas e bef ore
starting each horizontal line of video
display. When a
monochrome signal is being generated, there is no color burst
during t he back p orch.
VERTI CAL SYN C (Refer to Fig. 2)
A complete video image as seen on a TV screen is called a
frame. A frame consists of two interlaced vertical fields of 262.5
lines each. The ima ge is scanned twice at a 60Hz ra te (59.94Hz t o
be more precise), and the lines of Field 2 are offset to fall
between the lines of Field 1 (interlaced) to create a frame of 525
lines at a 30Hz r epetit i o n r a te.
At the b egi nning of each vertical fi eld, a p eri od equal t o several
horizontal lines is used for the vertical blanking interval. In a
television receiver, the vertical blanking interval prevents
illumination of the CRT during the vertical retrace. The vertical
sync pulse, which is within the vertical blanking interval, initiates
reset of the vertical deflection circuit so the electron beam will
return to the top of the screen before video scan resumes. The
vertical b lanking
interval begins with the first equal izing puls e, which consis ts of
six pulses one half the width of horizontal sync pulses, but at
twice the repetition rate. The equalizing pulse has an 8% duty
cycle. The vertica l sync pulse occurs immediately after the fast
equalizing pulse. The vertical sync pulse is an inverted
equalizing pulse at 92% duty cycle. The wide portion of the
pulse i s at t he -40 IEEE uni ts l evel a nd the narr ow porti on of the
pulse at the blanking level. A second equalizing pulse at 8%
duty cycle occurs after the vertical sync pulse, which is then
followed by 13 lines of blanking level (no video) and
horizontal sync pulses to assure adequate vertical retrace time
before resuming video scan. The color burst signal is present
after the second equalizing pulse.
Note that in Field 1, line 522 includes a full line of video,
while in Field 2 line 260 contains only a half line of video. This
ti ming rel at ions hip p roduces the interlace of Fields l and 2. The
NTSC color bars pattern generated by this instrument is
interlaced per NTSC sta ndards.
AMPLITUDE (Ref er to Fig. 1)
A standard NTSC composite video signal is 1 volt peak-to-
peak, from the tip of a sync pulse to 100% white. This 1 volt
peak-to-peak signal is divided into 140 equal parts called IEEE
units. The zero reference level for this signal is the blanking
level. The tips of the sync pulses are at -40 units and a sync
pulse is approximately 0.3 volt peak-to-peak. The portion of
the signal that contains video information is raised to a set-up
level of +7.5 units above the blanking level. A monochrome
video signal at +7.5 units is at the blac k threshol d. At +100 units
the si gnal repr esents 100%
13
THE N TSC CO LOR VIDEO SIGNAL (CONT.)
Fig. 2A. Compo site Video S ignal Showing Vertical Blanking Interval (Field 1).
14
THE N TSC CO LOR VIDEO SIGNAL (CONT.)
Fig. 2B. Composite Video Signal Show ing Vertical Blanking Interval (Field 2)
15
THE N TSC CO LOR VIDEO SIGNAL (CONT.)
white. Levels between +7.5 and +100 units produce various
shadi ngs of grey. Even when a compos ite video signal is not at t he
1 volt peak-to-peak level, the ratio between the sync pulse and
video must be maintained. 0.3 of total for sync pulse and 0.7 of
total f or 100% white.
There is als o a specific relationship b etween the a mplitude of the
composite video signal and the percentage of modulation of an rf
carrier. A t elevision signal uses negative modula tion, wherein the
sync pulses (-40 units) produce the maximum peak-to-peak
amplitude of the modulation envelope (100% modulation) and
white video ( +100 units) pr oduces t he mini mum amplitude of the
modulation envelope (12-
1/2% modulation). This is very
advantageous because the weakest signal condition, where noise
interfer ence ca n most easily ca use snow, is also the whit e portion
of the video. There is adequate amplitude guard band so t hat peak
white of +100 units does not reduce the modulation envelope to
zero.
COLOR
(R ef er to Fi g . 3)
The color information is a composite video signal consists of
three el ements: lumina nce, hue, and saturation.
Luminance, or brightness perceived by the eye, i s represented b y
the amplitude of the video signal. The luminance component of a
color signal is also used in monochrome receivers, which is
converted to a shade of grey. Yellow is a bright color and has a
high level of luminance (is nearer to white), while blue is a dark
color and has a low level of luminance (is nearer t o black).
Hue is the element that distinguishes between colors, red, blue,
green. etc. White, black and grey are not hues. The phase angle of
the 3.58MHz color subcarrier determines the hue. The three
primary video colors of red, blue, and green can be combined in
such a manner t o create a ny hue. A p hase shi ft of 360 ° will pr oduc e
every hue in the rainbow by changing the combination of red,
blue, and green.
Saturation is the vividness of a hue, which is deter mined by the
amount the color is diluted by white light. Saturation is often
expressed in percent: 100% saturation is a hue with no white
dilution which will produce a very vivid shade. Low saturation
percentages are highly diluted by white light and produce light
pastel shades of the same hue. Saturation information is contained
in the amplitude of the 3.58MHz color subcarrier. Because the
response of the human eye is not constant from hue to hue, the
amplitude required for 100% saturation is not the same for all
colors.
The combination of hue and saturation is known as chroma, or
chrominance. This information is normally represented by a
vector dia gram. Saturation is indicated by the l ength of t he vector
and hue is indicated by the phase angle of the vector. The entire
color signal representation is three dimensional, consisting of the
vector diagram for chrominance and a perpendicular plane to
represent t he amplit ude of luminance.
NTSC COLOR BARS SIGNAL
Refer again to Fig. 1. As mentioned previously, the chroma
amplitude required for 100% saturation of some hues is
considerabl y greater than for other hues. A lso, the luminanc e level
for each color differs. The NTSC color bars signal generates
standard EIA colors at the prescribed lumi
nance level
(brightness), c hr oma phase a ngle (hue), a nd chr oma amplitude
16
THE N TSC CO LOR VIDEO SIGNAL (CONT.)
Fig. 3. Elements of Color Television Signal
17
THE N TSC CO LOR VIDEO SIGNAL (CONT.)
(sat uration) set forth by the NTSC . This is the test signal
used i n broadca sting studi os and tra nsmitting eq uipment.
This makes the NTSC Generator a superior instrument
for servicing and adjusting col or televi sion receivers and
all types of other video equipment. An NTSC color bars
pattern is specified or recommended for most tests and
adjust ments i n video ca ssett e recorder s .
The precision of the NTSC color bars signal is beyond
compar ison with t hat of a low cost col or bar generator . A
color bar generat or us ually pr oduces al l hues at t he same
luminance level (or with no luminance component) and
same chroma amplitude, which of course is not equivalent
to the c olor signals being t ransmitted by br oadca st sta tions.
Many hues a re oversat urated. Als o, the chroma phas e angle
is normally produced b y using a c arrier that is offset enough
from 3.58MHz so that 360° phase shift occurs during each
horizontal line. This produces a gated rainbow pattern
rather than specific, phase controlled col ors.
18
CONTROLS AND INDICATORS
1. POWER Switch. Turns power on and off.
2. RGB TTL/LOW Switch. Selects TTL or low RGB output
level. When this switch is released (LOW position), a positive
logic state at the RGB output jack s (R, G, and B BNC jack s and the
RGB 9-pin D-type connector) is at 0.8V ±0.2V level. When this
switch is engaged (TTL p ositi on), the puls es are at a TTL level.
This switch also selects interlaced or progressive scan for
convergence patterns: when the switch is release
d the
convergence patt erns use interlaced scan, a nd then the switch is
engaged, the convergence patterns use progressive scan.
NOTE
The DOT, LINE, RAST, and NTSC BARS
switches are mechanically interlocked: i.e., se-
lection of a new pat tern a ut omatically r el ea ses t he
previous s electi on. Releasing all four switches by
partially pressing any one of them will provide a
color bats or staircase pattern with 100% white
level. The five selectable patterns are a vailab le at
the COMPOSITE VIDEO, IR/RF, or RGB
output jacks.
3. CONVERGENCE Switches. Select one of four availab le
convergence patt erns as f ollows:
Only LINE switch engaged:
A single vert ical and hor izonta l line i nters ecti ng at the cent er of the
screen.
LINE and 7 X 11 switches engaged:
7 horizontal lines a nd 11 vert ical li nes.
Only DOT s witch engaged:
A single dot at t he c enter of t he screen.
DOT and 7 X 11 switc hes engaged:
7 horizontal rows by 11 vertical columns of dots.
5. RAST Switch. Sel ects a black or bla nk raster pat t ern. Sync a nd
reference blac k are pr ovided for a bl emish free ras ter.
6. NTSC BARS Switch. Selects NTSC Color Bar pattern.
7. COLOR OFF Switch. Works in conj unction wit h NTSC BARS switch
and selects c olor or monochr ome (black a nd whit e) output. When t his
switc h is engaged, the col or subcarri er is switc hed off a nd the NTSC
BARS patt er n will be displa yed as sha des of grey. When this switch is
disengaged, the col or subcarrier is switched on and t he NTSC BARS
pattern will be displayed in color.
8. 4.5 MHz Switch. Turns 4.5MHz subcarrier (sound) on and off. When
this s witch is enga ged, a 4.5MHz sound c arrier (modulat ed by
19
CONTROLS AND INDICATORS (CONT.)
approximately 1KHz) is included in the signal at the IF/RF
output jack. When this switch is disengaged, no sound carrier
is included in the sig na l.
9. IF/RF Switch. Sets modulated output signal (at the IF/RF
output jack) to rf or i-f fr equency. When this s witch is engaged,
the signal at the IF/RF jack is at i-f signal frequency
(45.75MHz) and the CH 4/CH 3 switch has no effect. When
disengaged, t he si gnal at the IF/RF jack is at rf signal frequenc y
(61.25MHz for CH 3 or 67 .25 MHz for CH 4).
10. CH 4/CH 3 Switch. Works in conjunction with rf position of
IFIRF switch. Sets rf output carrier frequency to correspond to
CH 4 or CH 3. When the IF/RF switch is in the rf position
(disengaged) and this switch is disengaged (in the CH 3
position), t he outp ut signal at t he IF/RF jack corr esponds to TV
channel 3 (61.25MHz). When the IF/RF switch is in the RF
position (disengaged) and this switch is engaged (in the CH 4
position), t he outp ut signal at t he IF/RF jack corr esponds to TV
channel 4 (67.25MHz). When the IF/RF switch is in the IF
position (engaged), this switch has no effect on the output.
11. COMPOSITE VIDEO LEVEL Control. Adjusts level and
polarity of composite video signal at COMPOSITE VIDEO
output jack. Counterclockwise rotation produces a composite
video signal with negative going sync pulses (standard signal).
Full counterclockwise rotation of this control provides
maximum output signal with a calibrated level of 1Vp-p into
75Ω. Amplitude reduces to minimum at mid-point. Further
clockwise rotation reverses polarity (positive going sync) and
progressively increases amplitude. Full clockwise rotation of
this control provides an output signal with a level of
approximately 1 Vp -p i nto 75Ω.
12. COMPO SITE VIDEO Jack. Provides a video output for signal
substi tution di rectl y into the video circ uits of a t elevisi on receiver
and for t esting video recorders .
13. IF/RF Jack. Provides approximately 10mV rms (into 75Ω) rf
envelope modulated by composite video. Output carrier
frequency can be set to 45.75MHz (IF), 61.25MHz (CH 3) or
67.25MHz ( CH 4 ) by t h e C H 4/ CH 3 and IF/RF switches.
14. 30Hz Jack. Provides a 30Hz squar e wave TTL level output
useful for troubleshooti ng video recorders.
15. COMPosite SYNC Jack. Provides both horizontal and vertical
sync pulses for external use s uch as monitors requiring s eparat e
composite sync or sync trigger for an oscilloscope. Sync pulse
is negative polarity. Output impedance is 75Ω, level is TTL
compatible.
16. SYNC Vs Jack. Provides vertical sync pulses for external use
such as vertical sync for RGB monitors or sync trigger for an
oscilloscope. Sync is positive polarity. Output impedance is
75Ω. Level is TTL compatibl e.
17. SYNC Hs Jack. Provides horizontal sync pulses for external
use such as horizontal sync for RGB monitors or sync trigger
for an oscilloscope. Sync pulse is positive polarity. Output
impedance is 75Ω. l evel is TTL compat ible.
18. B Jack. Pr ovides blue output signal f or use with RGB monitors.
Output impedance is 75Ω and output level is switch selectable
(using the RGB TTL/LOW switch).
20
CONTROLS AND INDICATORS (CONT.)
Fig. 4. Controls and Indicators
21
CONTROLS AND INDICATORS (CONT.)
19.
G Jack
. Provides green output signal for use with RGB
monitors. Output impedance is 75Ω and output level is
swit c h s electa b l e ( using the RGB TTL/LOW switch).
20. R Jack. Provides red output signal for use with RGB
monitors. Output impedance is 75Ω and output level is
switch s electable ( using the RGB TTL/LOW switch).
21.
RGB 9-Pin D-Type Sub-Miniature connector
.
Provides red, green, blue, vertical sync (Vs), and
horizontal sync (Hs) signals. Pin layout and level
(TTL) are IBM Model 5153 PC monitor compatible.
Low level is also available by engaging the RGB
TTL/LOW switch.
22
OPERATING INSTRUCTIONS
WARNING
To prevent electrical shock, observe the
precautions listed in the TEST
INSTRUMENT SAFETY section, located on
the inside fr ont cover of thi s manual.
PRECAUTION AND TIPS
1. The most commonl y encountered hazard in the use of this
instrument is “hot chassis” equipment. Always connect an
isol ation trans former (suc h as the B & K Pre cision Model
TR-110 or 160 4 Isolati on Transformer or Model 1653 A or
1655A AC Power Supp ly) betw een the wall outlet and a ny
“hot chassis” equipment under test. See the TEST
INSTRUMENT SAFETY section, steps 7 and 8 for more
information
2. The RF/IF and COMPOSITE VIDEO outputs of this
NTSC Generator are rated to withstand voltages of -35 to
+35 volts. Al l other out puts a re rated t o withs tand -5 to +5
volts. The NTSC Generator must only be connected to
circuit points where the dc + ac peak voltage is within the
specified limit (±35 volts for the RF/IF and COMPOSITE
VIDEO outputs and ±5 volts for all other outputs). If in
doubt, make a volta ge measur ement f irst. Also t ake care t o
prevent acc identa l contact wit h high voltage points.
3. All outp uts have a source i mp edance of 75Ω. Therefore,
75Ω coaxial cable RG-59/U) is r ecommende d for
interconnecting c ables .
FAMILIARIZATION
To familia rize yourself with the op erating controls, capabilities
and operat ing char acteristics of the NTSC Generator, we
recom m end that you connect it to a color television receiver
that is in pr oper oper ating c ondition and observe all the
patterns. An oscillosc ope or wavefo rm monitor may al so be
used to observe all the wavefor ms produc ed.
INITI AL SET-UP
1. Connect t he power cord of the NTSC Generator to a
120VAC, 60Hz outlet
2. Turn on the i nstrume nt by setting the POWER switch to
the ON position (enga ged). The POWER indicator will
light w hen the power is on.
3. Apply power to the equip ment under test and turn it on.
For “hot cha ssis” equipment, use an i solat ion transformer .
23
OPERATING INSTRUCTIONS (CONT.)
4. RF Output
The rf outp ut of the NTSC G enerator may be app lied t o a televis ion
recei ver, video t ap e recorder or other video eq uip ment t unab le to
channel 3 or 4. Use the following procedure:
a. Connect a coaxia l cabl e from the IF/RF output j ack of t he
NTSC Generator to the antenna terminals. The 75Ω input
point is desir ed, or use 75Ω to 300Ω coupler.
b. Set the RF/IF swit c h on the Generat or to the RF position
(disengaged).
c. Set the c hannel s elector of the equipment under test t o channel
3 or channel 4, whichever i s not used for broadcas ting i n your
area.
d. Set the CH 4/CH 3 s witch on t he NTSC Generat or to t he
same channel that was selected on the equipment under test.
e. Patterns ma y now b e selected.
5. I-F Out put
The i-f output of the NTSC Generator may be injected into the i-f
section of television receivers, video tape recorders, or any other
video product using the standard 45.75MHz i-f frequency. Use the
following procedure:
a. Connect a pr obe to t he IF/RF output jack of the NTSC
Generator.
b. Set the RF/IF switch on t he Ge nera t or t o t he IF position
(engaged).
c. The probe may be used to inj ect the 45.75MHz i-f
signal at the desir ed point.
d. Patterns ma y now b e selected.
6. Composite Video Output
A composite video signal may be applied to the input
or injected at subsequent test points of non-rf
equipment such as video monitors, video distribution
amplifiers, signal processing equipment,
etc. A
composite video signal may also be injected into
circuit points after the video detector in television
receivers, video tape recorders, or other rf equipment.
The IF/RF and COMPOSITE VIDEO output jacks
may be used simultaneously if desired. Use the
following procedure:
a. Connect a coaxial cable or probe from the
COMPOSITE VIDEO jack of the Generator to
the desired point in the equipment under test.
b. Adjust the COMPOSITE VIDEO LEVEL
control to obtain the desired signal level and sync
polarity at the output jack. Fully counterclockwise
rotation gives maximum amplitude with negative
polarity sync. Clockwise rotation reduces level
and the center of rotation is minimum level.
Rotation past the c enter reverses the polarit y of the
signal to positive sync and further clockwise
rotation increases sig
nal level. Maximum
clockwise rotation is approximately 1Vp-p level,
although it is uncalibrated.
24
OPERATING INSTRUCTIONS (CONT.)
c. A calibrated 1Vp-p signal level with negative sync
polarity is available when the COMPOSITE VIDEO
LEVEL control is fully counterclockwise to the CAL
position.
d. Patterns ma y now b e selected.
NTSC STANDARD COLOR B AR PATTERN
1. Per f or m t he " IN IT IA L SE T-UP" proc edure.
2. Press the NTSC BARS switch. Be s ure that t he COLOR
OFF and 4.5MHz s witc hes are r eleased.
3. The NTSC Color Bar patt ern should now b e displa yed on the
screen.
STAIRCASE PATTERN
1. Per f or m t he " IN IT IA L SE T-UP" proc edure.
2. Press the NTSC BARS switc h and t he COLOR OFF
switches.
3. A monochrome bars (staircase) display with progressively
darker shades of grey should now be displayed (with the
light est baron t he left si de of the sc reen and the da rkest on t he
right side of screen) on the screen.
COLOR BARS WITH 100% WHITE
1. Perf orm the "INITIAL SET-UP" procedur e.
2. Release all of the pattern selection switches (the four
black pushbuttons) by slightly depressing one of them.
Ma ke s ur e t hat th e COLOR OFF switch is disengaged.
3. A color bars patter n with 100% white col or bar on t he
left side of the screen should now be displayed.
STAIRCASE WITH 100% WHIT E
1. Perf or m t he " IN IT IA L SE T-UP" proc edure.
2. Release all of the pattern selection switches (the four
black pushbuttons) by slightly depressing one of them.
Ma ke s ur e t hat th e COLOR OFF switch is engaged.
3. A monochrome bars display with progressively darker
shades of grey (left to right) should now be displayed
on the screen. The left most bar will be I00% white.
CONVERGENCE PATTERNS
1. Per f or m t he " IN IT IA L SE T-UP" proc edure.
2. Any of the f our convergenc e pat terns may be s elected b y
pressing t he appropriat e switc h(es) as f ollows:
25
OPERATING INSTRUCT IONS (CONT.)
Only LINE switch engaged:
A single vert ical and hor izonta l line i nters ecti ng at the cent er of
the screen.
LINE and 7 X 11 switches engaged:
7 horizontal lines and I I vertical lines.
Only DOT s witch engaged:
A single dot at the cent er of the screen.
DOT and 7 X 11 switc hes engaged:
7 horizontal rows by I I verti cal columns of dots.
3. Convergence patterns use interlaced scan when the RGB
TTL/LOW switch is released. This causes a slight jitter
effect i n the appearanc e of the patt ern. Progressi ve scan may
be selected by engaging the RGB TTI/LOW switch for a
jitter-free pattern. Most people prefer to use progressive
scan for convergence patterns, but some newer TV sets will
not accept the si gna l unless interlac ed sca n is used.
All convergence patterns are monochrome. On most sets the
entire 7 X 1 1 pat tern ( when 7 X 11 switch is engaged) will not be
visible due to overscan: it is desirable to display a pattern of at
least 7 horizontal a nd 10 vertical lines or dots.
BLACK RASTER PATTERN
1. Per f or m t he " IN IT IA L SE T-UP" proc edure.
2. Press the RAST switch. The COLOR OFF switch should
have no effect on the display regardless of whether it is
engaged or disengaged.
3. The screen s hould not b e c ompletely black (black raster or
black-burst).
4.5 MHz SUBCARRIER USE
To check for audio isolation, the 4.5MHz can be switched on
when the NTSC color bars pattern is selected. In a well designed
properly adjust ed receiver, the sound tra p should pr event the 4.5Hz
subcarrier from affecting the picture quality. In receivers where
the audio is not completely removed from the video component
of the signal, a "herri ng bone" patt ern will app ear on the sc reen.
To check the audio circuitry, the 4.5MHz switch should be
engaged when any pattern is selected. The 4.5MHz subcarrier is
modulated b y an a udio t one (approxi mat ely l KHz ) that ca n be us ed
to troub leshoot the audio circuitry in video equipment.
RGB OUTPUT
Independent red, green, and blue (RGB) outputs are available
for testing and adjusting color monitors that use separate red,
green, and blue inputs rather than a composite video input. Such
color monit ors are of ten us e d wi th c o mp uter s havi n g c ol or grap h ic
display capabilit y, etc.
The Model 1249B will provide compatible test s ignals f or most
RGB monitors using sta ndard 525 line, 15 .750KH z horiz ontal
26
OPERATING INSTRUCT IONS (CONT.)
scan. It is no t compatible with high resolution graphics monitors
which use special high frequency scan rates.
Some color monitors accept either composite video signals or
RGB signals. Often, positive polarity vertical and horizontal sync
is required in RGB monitors. Some RGB monitors use low level
RGB signals and vary color saturation in response to analog
changes of the signal level. Others use higher TTL level excitation
and display only fully saturated colors- The Model 1249B NTSC
Generator pr ovides si gnals for most versions.
Separate R, G, and B outputs with selectable TTL or LOW
level are available at BNC connectors on the front panel. In
addition, positive polarity Vs (vertical sync) and Hs (horizontal
sync) are a vailable at additi onal BNC c onnect or s, als o on the fr ont
panel. To simplify connections, a 9-pin connector (sub-miniature
D-t ype) i s provided whic h mates with the 9-pin connector used on
the most common RGB monitor configuration (the connector is
IBM PC c ompati ble). This duplicat es the functions of the R, G , B
Vs, and Hs jacks in one connector so that all connections are
made simultaneousl y with a single cabl e.
The procedure for using the RGB outp uts is as follows:
1. Connect the RGB outputs of the NTSC Generat or to the
in p uts of t he c ol or m oni t or .
a. Connect the R, G, and B outputs of the G enerator to the
corresponding red, green, and blue i nputs of t he c olor
monitor.
b. If composite sync is required, connect the
COMPOSITE SYNC output of the Generator to the
sync input of the monitor.
c. If separate vertical and horizontal positive polarity sync is
required connect the Vs and Hs outputs of the generator to
the corresponding vertical and horizontal sync inputs of the
monitor.
d. If the color monitor is equipped with a 9-pin connector that
mates with t he RGB r eceptacl e on the Generator, connect it.
Al l n ecessar y connections are made simultaneously.
2. Select TTL or LOW level a s appropriat e for t he monitor
being tested.
3. Select the desired pattern.
WA VEFOR M M ONIT ORI NG
It is often desirable to examine the waveform on an oscilloscope
or waveform monitor. For example, in troubleshooting a television
receiver, the COMPOSITE VIDEO output may be applied to an
oscilloscope or waveform monitor and the waveform used for
reference. Meanwhile, the rf or i-f output which is modulated with
the same wa veform ma y be ap pl ied at var ious points i n the eq uip ment
under test. The waveform measured at the video detector of the unit
under tes t may be c ompared to the reference waveform generated by
the NTSC Generator. Degradation of the waveform indicates poor
circuit performance or misadjustment. A dual trace oscilloscope is
very h a n d y for s uch w a ve -f orm compar ison.
1. Connect a coaxial cable fr om the COMPOSITE VIDEO
output jack to the vertical input of the oscilloscope.
Terminate i nto 75Ω.
27
OPERATING INSTRUCT IONS (CONT.)
2. Connect anot her cable fr om t he
COMP SYNC
output
jack to t he exter nal tri gger input of t he oscillosc ope.
3. Select the external triggering mode on the oscilloscope.
4. A sweep rat e of ab out 10µs/di v is a ppropriat e for
viewing horizontal tines of composite video, 2 ms/ div
for viewing vertical fields, and 5 ms/div for viewi ng
vertic al fra mes. The s weep vernier may be us ed for ti ne
adjustment of the wavefor m displa y.
SIMULT ANEOUS OUTPU TS
For maximum flexibility, all output jacks may be used
simultaneously if desired. This can be a valuable aid in many
applica tions . Thes e outp uts are s ummarized as foll ows:
The COMPOSITE VIDEO output is continuously
available when the instrument is operating. The video
component of the si gnal is dependent upon the s elect ed
pattern.
The IF/RF output is continuously available when the
instrument is operating. It may be set to operate on
channel 3, channel 4, or i-f frequencies. It is modulated
by the same signal that appears at the COMPOSITE
VIDEO output jack (however. level is fixed and sync
pulse i s negat i ve going), a lthough t he modula t ed 4.5M Hz
subcarrier can be added.
The COMP SYNC, Vs, Hs, and 30 Hz are also
continuously available. The COMP SYNC output
supplies negative polarit y sync, and the Vs and Hs sync
outputs supply positive polarity signals. The 30Hz
signals is a TTL level square wave useful for video
recorder tr oubleshooti ng.
28
APPLICATIONS
NTSC COLOR BARS
Versatility
The N TSC c olor ba rs pa tter n is th e basi c pa ttern us ed for
most testing, troubleshooting and adjustments in video
equipment. It is one of the most valuable and versatile
color pa tter ns ever de vise d. T he NTS C col or ba rs patt ern is
very effective for adjusting any type of consumer or
industrial color video equipment for maximum
performance. For troubleshooti ng and s ervici ng, anal ysis of
the NTSC color bars pattern or its waveform usually
localize a color related problem to a specific few circuits.
Color Television Receivers
The NTSC color bars pattern provides a standard
reference for color adjustments and troubleshooting in
television receivers. The pattern contains bars of the three
primary colors: red, blue, and green. These are good
reference for checking 3.58MHz phase problems. The grey,
yellow, cyan, a nd magenta help define pr obl ems wher ein the
mix of colors is not in the correct proportions. The
COLOR OFF switch removes the chroma component
entirely and is very helpful in defining problems as either
chro ma or l u mina nce r elated.
Video Recorders
The NTSC color bars pattern is virtually a necessity for
video rec order servici ng. This i ncludes video c assett e
recorders a nd video disc players.
Most manufacturers specify an NTSC color bar input signal
in their literature. Adjustment procedures are usually based
upon an N TSC color bar input, and the wa vefor ms s hown at
various points on the schematic diagram are those obtained
with an NTSC color bar input. Some manufacturers provide
"field" a nd "factory" pr ocedures in t heir literat ure. However,
the "field" procedures merely eliminate all adjustments that
require an NTSC color bars pattern which severely restricts
the amount of servicing that can be performed. With an
NTSC generator you can perform the "factory" procedures.
The NTSC color bars pattern is essential for chroma and
luminance alignment and is also preferred for general
troubleshooting.
Overall VCR Performance
An overall performance test of a VCR may be conducted
by recording the NTSC color bars pattern then playing it
back on a video monitor. There should be no noticeable
differenc e between the video pla yed back from the VCR and
an NTSC c olor bars pa ttern appl ied dir ectly t o t he monitor.
Luminance a nd Chroma Bala nce
In a VCR, the luminance and chroma signals are
separated during the recording process and recombined
during the playback process. If luminance and chroma
signals are not maintained at the proper proportions when
separated, color distortion will probably occur, particularly
in the vividness of colors or color saturation. Wavefor ms
29
APPLICATIONS (CONT.)
may be exam-fined throughout t he VCR for p roper luminance
to chroma proportions. Another problem that may be
encountered is a difference in delay between the luminance
signal and the chroma signal. This will cause fuzziness along
the edges of the color bars.
STAIRCASE
The staircase pattern (NTSC BARS and COLOR OFF
switches engaged) is recommended for frequency equalization
adjustment in the recorder amplifier circuit of VCR's. The FM
signal which carries luminance information in a VCR is shifted
to a different frequency with each step of the staircase signal.
However, record current should remain constant across the FM
frequency band. Frequency equalization should be adjusted so
that record current is equal for all steps of the staircase input
signal.
CONVERGENCE
Center Cross Pattern
The center cross pattern (LINE switch engaged. 7 X 11
switch disengaged) should intersect at the center of the screen
and there should be no tilt of the horizontal line. Improper
centering indicates the need for centering adjustment or a
deflection circuit fault. Tilt may require repositioning of the
deflection yoke for correction. This pattern also provides a
good genera l c heck of verti cal and hor iz ontal sync.
Center Dot Patter n
Some technicia ns and engineers prefer to us e a cent er dot for
centering adjustment.
Dots Pattern
The dots pattern (DOT and 7 X 11 switches both engaged)
is used for static convergence, usually by converging the
center dot of the pattern. A 7 x I 1 dot pattern is generated.
Most sets have some overscan so that all dots are not visible,
except possible under l ow voltage condi tions. Some set s have
a tendenc y towa rd mor e overs c an tha n ot hers . It is desirab le to
displa y at least a 7 x 9 dot pattern.
Crosshatch Pattern
The crosshatch pattern (LINE and 7 X 11 switches both
engaged) is normally preferred for dynamic convergence,
although some technicians prefer the dots pattern for both
static and dynamic convergence. The crosshatch pattern
checks vert ical and hori z ontal linea ri ty. Eac h s quare s houl d be
the same size which is a convenient reference for making
linearity adjustments. The crosshatch pattern is also used to
check pi ncushi on distorti on whic h often app ears at the out side
edges of lar ge screen TV s ets as bends i n the lines .
RF and I -F
The tuners and i-f sections of VCR's and color television
receivers are essentially the same. Servicing of these sections
can b e aided b y the rf and i-f output s of the NTSC Generator.
Performance of the VCR or TV set should be nearly as good
when using the rf signal on channel 3 or 4 as when applying
compos ite video dir ect ly into t he video sec tion. If not, there is
a problem in the tuner or i-f section which can be isolated by
injecting rf or i-f signals at various points and identifying the
point at which norma l opera tion is lost.
30
APPLICATIONS (CONT.)
SYNC
The NTSC color bars and staircase pattern include NTSC sync
pulses, the same type as those produced by a broadcast station.
The sync amplitude of 40 IEEE units is often the reference
against which the remainder of the luminance signal is compared.
Circuits can be checked for sync clipping by observing the
staircase pattern on an oscilloscope and checking whether the
sync puls e amplitude r emains at 0.53 c ompared to the 75% white
step (grey) which is a reference of 1.0. AGC circuits, which
respond to sync pulse amplitude can be checked by using the
COMPOSITE VIDEO output and varying the level. The
overall amplitude of the video can be varied but the sync pulse
amplitude is a consta nt p ercentage of the total video a mplitude.
The precise timing of the sync pulses allows proper adjustment
of servo circuits which control tape speed in VCR's and switching
circuits which should switch between video heads to allow a
continuous t ransition fr om fi eld to fi eld.
30Hz OUTPUT
Due to their electro-mechanical nature, servos are a common
problem with VCR's. Using standard troubleshooting techniques
and tools, isolating a servo problem can be very difficult if not
impossible. Using the 30Hz output of the NTSC Generator
however, should allow relatively simple isolation of the trouble
spot.
VCR's utilize closed loop feedback circuits to control the heads.
By injecting the 30Hz signal at different points in the closed loop,
the faulty circuit should be relatively easy to isolate. For example,
if you were to i njec t th e 3 0 Hz si gn al f rom t h e G en era t or i nt o the
feedback path and no change in servo operation was noted, the
problem would be with the circuit that receives the feedback
signal. Conversely, if you noticed a change in the servo
operation, the problem would be in the circuit that sends the
feedback signal.
CCTV APPLICATIONS
Closed circuit television systems do not usually include a
built-in NTSC color reference signal. The NTSC Generator can
be used to supply such a reference. All equipment in the system
can t hen be a djusted t o the same refer ence while connected into
or removed from the system.
Virtually all equipment used in CCTV systems is designed
around certai n standard s ignal c ondit ions at t he input and out put
terminals. This allows equipment to the compatible, without
modification, when inter-connected as a system. Among the
standard signal conditions are positive polarity video signal
(negative sync pulses). 1 volt peak-to-peak signal amplitude
75Ω impedance and unbalanced line (one side grounded). The
NTSC Generat or has these characteristics w hich si mplifies s et-
up for t esting, troubl eshooting a nd a djus t me nt.
CATV APPLICATIONS
Cable television systems also use the standard signal
conditions specified in the "CCTV Applications" paragraph at
input and output terminals. The channel 3 or 4 rf output of the
unit ca n be used throughout a CATV network to test, adjust, or
troubles hoot amplifi ers, cabl es, and a ny ot her equipment.
31
APPLICATIONS (CONT.)
MATV APPLICATIO NS
Master antenna systems for hotels, motels, apartment
buildings, etc. can be check ed by applying the cha nnel 3 or 4
rf output of the Generator to the input of the network (or a
branch of the network) and examining the pattern obtained
on channel 3 or 4 directly from the screen of each TV set.
To isolate problems in the distribution network from
problems i n an individual TV s et, apply the c hannel 3 or 4 rf
output of the NTSC Generator directly to the antenna
terminals of the TV set. A proper display on the screen
indicates that there is a problem i n the distrib ution network.
VECTORSCOPE MEASUREMENTS
A vectorscope measurement is usually more helpful for
trouble analysis than observing the pattern displayed on the
picture tube. If an NTSC Vectorscope is available, it is
recommended. The display on an NTSC Vectorscope with
the NTSC c olor bars patt ern app li ed should b e six dot s located
withi n the si x smal l boxes of the Vect orsc ope as shown i n Fig.
3. The displayed vector pattern may be extracted from
anywhere in the composite video or 3.58MHz color circuits.
Amplitude must be initially adjusted so the color burst aligns
with the 75 % mark on the vect orscop e gratic ul e.
If an NTSC vectorscope is not available, the demodulated
color signals from the red and blue guns can be used as the
X and Y i nputs to a good la boratory oscill oscope (such as the
B+K Precision Model 2120). The resulting display is a
vectorscope pattern as shown in Fig. 7. The oscilloscope
should be s et up f or vect orscope operation as f ollows:
1. Select the NTSC BARS pattern and apply to the TV set
under test.
2. Set up to the oscilloscope for X-Y operation. Adjust the
position controls to center the dot on the screen with no
signal Input t o th e osc i ll os cop e .
3. Connect the X and Y inp uts of t he oscilloscop e to the r ed gun
as shown in Fig. 5.
4. Adjust the vertical and horizontal oscilloscope gain to equal
amounts. This will cause the spot to become a 45° line as
shown in Fig . 5.
5. Leave the vertical ( Y) input c onnect ed to the r ed gun but
move the horiz ontal i nput to t he bl ue gun as s hown in Fig. 6.
6. A display similar to that shown in Fig. 7 shoul d be obtained.
However, several factors may affect the display as follows:
a. The HUE control of the TV under test will rotate the
display. The HUE control may be adjusted to obtain the
display nearest to that shown in Fig. 7. Starting from a
centered position, the HUE control can typically rotate
the display ±30
b. The COLOR control of the TV under test (chroma
amplitude) adjusts the amplitude of the display. This
control should typically be adjusted for the highest
amplitude obtainable without distortion (just below the
point where further rotation of the control does not
increase amplit ude of display).
32
APPLICATIONS (CONT.)
d. The display shape depends upon the chroma bandpass,
demodulator alignment, and design of the TV chassis.
The better the alignment and bandwidth, the closer the
vector waveform will be to the ideal waveform.
e. Display shape will vary depending upon whether TV
chassis uses 90° or 105° angle of demodulati on.
7. The vectorscope pattern can be a valuable tool for
troubleshooting color problems, including improper
alignment and adjustment, if the normal vectorscope
pattern is known. However, since normal patterns vary
consi derably fr om one TV to anot her, a library of nor mal
displays measured from various popular TV chassis in
good working conditi on is desirable f or refer ence.
Fig. 5. Using a Conventional Oscilloscope
as a Vectors cope, step 1 (set-up).
Fig. 6. Using a Conventional Oscilloscope a s a Vectorscope,
step 2 (set-up).
33
APPLICATIONS CONT.)
Fig. 7. Typical Vectorscope Display of Demodulated
Color Bars Pat tern Viewed o n Conventional Oscilloscope.
34
MAINTENANCE
WARNING
The following instructions are for use by
qualified service personnel only. To avoid
electrical shock, do not perform servicing
unless you ar e qua lified to do so.
A shock ha zard is pre sent when the top cover
is removed if the power cord is plugged into
an ac outlet. AC line voltage may be present
on the fuse holder, line cord receptacle,
POWER switch, and power transformer
even when the POWER switch is off.
CASE REMOVAL
In order t o replac e the fuse or cal ibrat e the N TSC Genera tor t he
case must be removed. To remove the case, perfor m the foll owing
steps:
1. Turn the Generator upside down and remove the four screws.
2. Lift the bottom hal f o f t he ca s e st ra i ght up.
FUSE REPLACEMENT
If the f use blows t he pil ot light will go out a nd the G enerator wil l
not operate. The fuse should not open unless a problem has
developed in the unit. Determine and c orr ect t he cause of the
blown fus e, then r eplac e only with a 1/16A, 250V sl ow blow
fuse (B +K Precision Part No. 198-303-0-062). The f use is
only accessible by removing the case. For fus e location r ef er
to Fig. 8 .
CALIBRATION
This unit was carefully checked and calibrated at the
factory prior to shipment. Readjustment is recommended
only if repairs have been made in a circuit affecting
calibration. The location of the calibration adjustments is
shown in Fig. 8. Keep in mind that some calibration
procedures require high precision test instruments. Those
adjustments should be attempted only if the proper test
equipment is available and you are experienced in its use.
The following test equipment is required for complete
calibration:
• NT SC Vec t orsc op e .
• Wa ve for m M on it or .
• Frequency Counter with l ppm time b ase accuracy.
B+K Precision Model 1856D or eq ui valent.
1. Before begi nning calibra tion, t urn on t he NTSC
Generator a nd allow 15 minutes of warm-up time.
2. Engage COLOR OFF and BAST sw itches. A ll other
swit c h es (e xc ept POWER) should be disengaged.
35
MAINTENANCE (CONT.)
R7
Fig. 8. Adj ustment an d T est P oint Lo cat io ns.
36
MAINTENANCE (CONT.)
3. Connect the Waveform Monitor and the Vectorscope to the
COMPOSITE VIDEO jack (t erminat ed into 75 S2) . Set the
Waveform Monitor response to FLAT and the sweep to 2H.
Set the variable a mplitude control on t he Wavefor m Monitor
to the CAL positi on. Set t he sync to internal, and turn on the
DC rest orer.
Color Subcar rie r Adj ustment
1. Connect the fr equency count er at the junc tion of R95 and pin
6 of IC1 (the ri ght hand si de of R95) and a dj ust C4 for a
readi ng of 3.579545 MHz ±3Hz on the freq uenc y count er.
Sound Subcarrier Adjustment
1. Press the 4.5M Hz switch on t he Genera tor
2. Connect the frequenc y count er at the junc tion of R81 and pin
13 of IC18(t he back lead of R81) and adjust L4 for a readi ng
of 4.49MH z ±10k Hz on the frequenc y count er.
3. Release the 4.5 MHz switch on the NTSC Generat or.
I-F a nd RF Adjustme nts
1. Ma ke s ur e t hat th e CH 4/C H 3 switc h is disengaged (i n the
CH 3 position), connect the frequency counter to the IF/RF
jack, a nd adjust t he c ore of L2 f ully clockwis e (to t he
bottom) or until t he frequenc y counter reads below
61.245MHz.
2. Now adjust L2 count erclockwise unt il t he frequency
counter reads 61.250MHz ±5KHz . T ur n t he c or e an
additional 1 /2 t urn counter-cl ockwise. The r eadi ng on the
frequency c ounter shoul d r etrain stable.
3. Pr es s t h e CH 4/CH 3 switch on th e NTS C Gen erat or ( so th at it
is in the CH 4 position).
4. With the frequency counter still connected to the IF/RF jack,
adjust th e core of L3 full y clockwise (to th e bottom) or unt il the
frequency counter reads below 67.245MHz.
5. Now adjust L3 counterclockwise until the frequency counter
reads 67.250MH z ±5KHz. Turn the core an additiona l 1/2 turn
counter-clockwise. The reading on the frequency counter
should remain stable.
6. Press th e IF/RF switch on th e Generator (so tha t it is in th e IF
position).
7. Adjust the core of LI fully clockwise (to the bottom) or until
th e f r equ en c y c ounter reads b elow 45.745MHz.
8. Now adjust L I counterclockwise' until the frequency counter
reads 45.750MHz ±5 KHz. Turn the c ore an additional 1/2 tu rn
counter-clockwise. The reading on the frequency counter
should remain stable.
9. Release the IF/RF switch (return to channel 4 rf operation).
The counter should now read 67.250MHz ±5KHz. If the
readin g is un stab le, repeat st ep 5.
10. Release the CH 4/CH 3 switch. The switch should now be in
the CH 3
position. The frequency counter should now read
61.250MHz ±5KHz. If the reading is unstabl e, repeat step 2.
Sync Pulse Adjustment
1. Set the COMPOSITE VIDEO LEVEL control to CAL
position and adju st VR8 for sync pulse amp litude of -40 IRE on
the Waveform Mon itor (baselin e on zero line).
37
MAINTENANCE (CONT.)
2. Press the NTSC BARS switch a nd r el eas e th e COLOR
OFF s witch. Set the Wa veform Moni tor for a sweep
speed of 1µs/div.
3. Adjust VR10 and VR11 on the 1249B for minimum
ripple on the bottom edge of the sync pulse. Repeat until
no furt her improveme nt is p ossib le .
Color A djustme nts
1. Adjust t he vertical and horizontal positi on controls on the
Vector-scope so that the dot is exactly centered on the
screen and make sure that the gain control is adjusted for
sync pulse amplit ude of -l0 IRE.
2. Press the NTSC BARS s w i tch a nd r elea se t h e COLOR
OFF switch on the Generat or.
3. Adjust VR12 on the NTSC Generator to align the burst
vector with the mark on the horizontal axis of the
Vectorscope. Readjust the phase control on the
Vectorscope if necessar y.
4. Adjust VR4 and VR9 on the Generator to bring t he r ed
vector into the small R box on the Vectorscope display.
5. Adjust VR6 t o bring t he bl ue vector i nto the s mall B b ox
on the Vectorscope display.
6. Adjust VR5 to bring the green vector into the small G
box on the Vectorscope display.
7. If necessary, readjust VR12 to align the bunt vector
with the proper mark. Also if necessary, readjust VR4,
VR5, VR6 and VR9 to bring all six vectors into their
proper boxes.
8. Return the Waveform Monitor sweep switch to 2H and
adjust VR7 on Generator for grey level of 77 IRE on the
Waveform Monitor. Recheck Vectorscope display and
rea d jus t vec t ors if nec ess a ry.
9. Release all of the pattern selection switches (the four light
colored pushbuttons) by slightly depressing one of them.
With the Waveform Monitor sweep switch still set on 2H,
adjust VR20I on the Generator for a white level of 100 IRE
units on the Waveform Monitor. Engage the NTSC BARS
switch.
10. Adjust VR2 on the G enerator s o that t he black c olor bar the
last one) is 2.5 divisi ons wide on the Waveform Moni tor. If
waveform jitters, readjust VR2 slightly so that spacing is
between 2.5 a nd 2.0 divisions.
11. Press the LINE and 7 X 11 switches on the NTSC
Generat or. Adjust VR3 so that the top horizontal l ine of the
Wavefor m Monit or disp lay is at 100 IRE.
12. Adjust VR1 fully counterclockwise. If the tops of the
vertical lines on the Waveform Monitor display are not at
100 IRE, a dj us t V R1 until t hey are.
INST RUMEN T RE P AI R S ERVI C E
Because of the specialized skills and test equipment
required for
instrument repair and calibration, many
customers prefer to rely upon B&K Precision for this
service. We maintain a network of B&K Precision
authorized service agencies for this purpose. To use this
service, even if the instrument is no longer under warranty,
follow the instructions given in the WARRANTY SERVICE
INSTRUCTIONS. There is a nominal charge for instruments
out of warrant y.
38
SERVICE INFORMATION
Warranty S ervi ce: Please return the product in the original packaging with proof of purchase to the address below. Clearly state in writing
the performance problem and return any leads, probes, connectors and accessories that you are using with the device.
Non-Warra nty Service: Return the product in the original packaging to the address below. Clearly state in writing the performance problem
and return any leads, probes, connectors and accessories that you are using with the device. Customers not on open account must include
payment i n the form of a money order or credit card. Fo r the most curr ent repair charges please vi sit www.bkprecision.com and click on
“service/repair”.
Return all merchandise to B&K Precision Corp. with pre-paid shipping. The flat-rate repair charge f or Non-Warranty Service does not include
return shipping. Return shipping to locations in North American is included for Warranty Service. For overnight shipments and non-North
American shipping fees please contact B&K Precision Corp.
B&K Pr ecision Corp.
22820 Savi Ranch Parkway
Yorba Linda, CA 92887
www.bkprecision.com
714-921-9095
Include with the returned instrument your complete return shipping address, contact name, phone number a nd descri pti on of
problem.
39
LIMITED ONE-YEAR WARRANTY
B&K Precision Corp. warrants to the original purchaser that its products and the component parts thereof, will be free from defects in
workmanship and materials for a period of one year from date of purchase.
B&K Precision Corp. will, without charge, repair or replace, at its option, defective product or component parts. Returned product must be
accompanied by proof of the purchase date in the for m of a sales recei pt.
To obtain warranty coverage in the U.S.A., this product must be registered by completing a warranty registration form on
www.bkprecision.com within fifteen (15) days of purchase.
Exclus ions: This war ranty does not apply in the event of misuse or ab use of the p rod uct or a s a result of u nauthorized a lterati ons or
repairs. The w arranty is void if t he serial number is altered, def aced or remove d.
B&K Pr ecision Corp. shall not be liable for any consequential damages, including without limitation damages resulting from loss of use.
Some states do not allow limitations of incidental or consequential damages. So the above limitation or exclusion may not apply to you.
This warranty gives you specific rights and you may have other rights, which vary from state-to-state.
B&K Pr ecision Corp.
22820 Savi Ranch Parkway
Yorba Linda, CA 92887
www.bkprecision.com
714-921-9095
40
TEST I NSTRUMEN T SAFETY (CONT.)
(continu ed from insid e front c over)
7. Testing "hot chassis" video-equipment is especially hazardous unless the proper safety precautions are taken. Most recent television
receivers and other equipment with a two-wire ac power cord are the “hot chassis" type: this even includes many with polarized power
plugs. A plasti c or wooden cabinet usually in sulat es the chassi s to prot ect the cust omer but when the cabin et is remo ved for ser vicing th ere
is gr eat danger of s erious elect rical sh ock i f the chassi s is touched. To prevent electrical sh ock, always connect an is olation t ransformer
between th e ac out let and an y hot chassis eq uipment und er test. Th e B+K Precision Model 1604A or TR-110 Isola tion Transformer, or
Model 1653A or 1655A AC Power Supply is suitable for most applications. To be on the safe side, treat all two-wire ac powered
equip ment as "hot cha ssis " unless you are su re it has an is olated cha ssis or an earth ground cha ssis. Use of an isolati on t ransformer has no
disadvantage, even if it is not required.
8. In addition to the hot chassis shock hazard mentioned in Item 7, severe damage to test instruments or the equipment being tested is
probab le from conn ecting a cable between the NTSC Generator and any "hot chassis " equipment unless an is olation transformer is used.
The antenna terminals of a h ot chassis set should alread y b e isolated from the cha ssis , unless d efective, an d the isolat ion trans former may
not be req ui red . For c onn ecti on t o an y ot h er point , an isolati on tran sformer is n eeded.
9. Capacitive coupled outputs of the Model 1249B NTSC Generator are rated at ±35 volts (DC + AC peak) maximum: this includes the
IF/RF and COMPOSITE VIDEO jack. All other input and output jacks are direct coupled and are rated at ±5 volts (DC + AC peak)
maximum. Make test connections at circuit points which do not exceed this value. If in doubt, first make voltage measurement with
voltmeter or osci lloscope. Conn ection t o higher voltage ma y damage the equipment.
10. When testin g an y ac powered equipment, rememb er that ac line volt age is usually pres ent on some power inpu t circuit s such as the on -
off s witch, fuses, p ower t rans former, etc. an y tim e th e equipm ent is c onn ected t o an ac outlet, even i f the equ ip ment i s tu rn ed of f.
11. Servicin g of this unit should be performed only by quali fied electronics technicians who are trained to work safely in the presence of high
voltage.
12. Never work alone. Someone should be nearby to render aid if necessary. Training in CPR (cardio-pulmonary resuscitati on) first aid is
highly recommended.
