INSTRUCTION MANUAL Model 1249B
Contents
1. 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 within this interval Vertical Resolution Smallest increment of a television picture that can be discerned in the vertical plane This increment is dependent upon the number of lines of scan per 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 to achieve interlaced scan THE NTSC COLOR VIDEO SIGNAL 1 m EL Tm bees se ap mj mm maen we Fig 1 Composite of Video Signal One Horizontal Line of NTSC Color Bars Signal HISTORY In 1953 the NTSC National Television Systems Committee established the color television standards now in use by the television broadcast industry in the 11 United States and many other countries It was of course2. 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 579545MHz subcarrier contains the color information The phase angle of the subcarrier represents the hue the amplitude of the subcarrier represents saturation HORIZONTAL SYNC Refer to Fig 1 The beginning of a line horizontal scan occurs at the leading edge of the horizontal blanking pedestal In a television receiver the horizontal blanking pedestal starts as the electron beam of the CRT reaches the extreme right hand edge of the screen plus a little overscan in most cases The horizontal blanking pedestal prevents illumination of the screen during retrace that is until the electron beam deflection circuits are reset to the left edge of the screen and ready to start another line of video display The entire horizontal blanking pedestal is at the blanking level or the sync pulse 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 front porch the horizontal sync pulse and the back porch The front porch is a 1 40 microsecond period at second THE NTSC COLOR
3. considerably greater than for other hues Also the luminance level for each color differs The NTSC color bars signal generates standard colors at the prescribed luminance level brightness chroma phase angle hue and chroma amplitude THE NTSC COLOR VIDEO SIGNAL CONT Darker R Y _ luminance lighler 1 Yellow 168 Burst Saturation 1 Cyan 303 LIN 284 Cyan Standard color phase vector diagram 3 Dimensional concept of color Fig 3 Elements of Color Television Signal 16 THE NTSC COLOR VIDEO SIGNAL CONT saturation set forth by the NTSC This is the test signal used in broadcasting studios and transmitting equipment This makes the NTSC Generator a superior instrument for servicing and adjusting color television receivers and all types of other video equipment An NTSC color bars pattern is specified or recommended for most tests and adjustments in video cassette recorders The precision of the NTSC color bars signal is beyond comparison with that of a low cost color bar generator A color bar generator usually produces all hues at the same 17 luminance level or with no luminance component and same chroma amplitude which of course is not equivalent to the color signals being transmitted by broadcast stations Many hues are oversaturated Also the chroma phase angle is normally produced by using a carrier that is offset enough from 3 58MHz so that 360 pha
4. 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 oscillator is phase locked to the color burst reference phase before starting each horizontal line of video display When a monochrome signal is being generated there is no color burst during the back porch VERTICAL SYNC 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 image is scanned twice at a 60Hz rate 59 94Hz to be more precise and the lines of Field 2 are offset to fall between the lines of Field interlaced to create a frame of 525 lines at a 30Hz repetition rate At the beginning of each vertical field a period equal to several horizontal lines is used for the vertical blanking interval In a television receiver the vertical blanking interval prevents illumination of the C
5. location of its high voltage points However remember that high voltage may appear at unexpected points in defective equipment 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 Use the time proven one hand in the pocket technique while handling an instrument probe Be particularly careful to avoid contacting a nearby metal object that could provide a good ground return path When testing video equipment that includes a picture tube or CRT remember that the high voltage power supply and CRT anode operate 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 high voltage pints Also avoid bumping the CRT with a sharp edge Because of the high vacuum a nicked CRT may implode and cause flying glass fragments continued on inside rear cover 2 TABLE OF CONTENTS Page Black Raster Pattern eere TEST INSTRUMENT SAFETY es inside front cover i E AD INTRODUCTION 4 RGB Output Waveform Monitoring FEATURES ncecsccssccsesssscsessecsseesecsucsueesucsussssesucsueesecsussaeesecsussusesecause
6. with high voltage points 22 3 outputs have a source impedance of 75Q Therefore 75Q coaxial cable RG 59 U is recommended for interconnecting cables FAMILIARIZATION To familiarize yourself with the operating controls capabilities and operating characteristics of the NTSC Generator we recommend that you connect it to a color television receiver that is in proper operating condition and observe all the patterns An oscilloscope or waveform monitor may also be used to observe all the waveforms produced INITIAL SET UP 1 2 Connect the power cord of the NTSC Generator to 120VAC 60Hz outlet Turn on the instrument by setting the POWER switch to the ON position engaged The POWER indicator will light when the power is on Apply power to the equipment under test and turn it on For hot chassis equipment use an isolation transformer OPERATING INSTRUCTIONS CONT RF Output The rf output of the NTSC Generator may be applied to a television receiver video tape recorder or other video equipment tunable to channel 3 or 4 Use the following procedure a Connect a coaxial cable from the IF RF output jack of the NTSC Generator to the antenna terminals The 75Q input point is desired or use 722 to 300Q coupler Set the RE IF switch on the Generator to the RF position disengaged Set the channel selector of the equipment under test to channel 3 or channel 4 whichever is not used for broadcasting in
7. BK PRECISION INSTRUCTION MANUAL Model 1249B is lt 22 NTSC GENERATOR TEST INSTRUMENT SAFETY WARNING Normal use of test equipment exposes you to a certain amount of danger from electrical shock because testing must sometimes be performed 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 low as 35 volts dc or ac rms should be considered dangerous and hazardous since it can produce a lethal 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 cables are at earth ground Don t expose high voltage needlessly to the equipment under test Remove housings and covers only when necessary Turn off equipment while making test connections in high voltage circuits Discharge high voltage capacitors after removing power If possible familiarize yourself with the equipment being tested and the
8. GB signals for computer and static and dynamic convergence video monitors with standard 525 line 15 750KHz scan D Type sub miniature connector provides red green blue BLACK RASTER horizontal sync and vertical sync signals and is Model 5153 PC monitor compatible Output level is switch Provides sync and reference black for a clear blemish free selectable between TTL and LOW 0 8x0 2V raster 30Hz OUTPUT CRYSTAL OSCILLATORS 30Hz TTL output is useful for video recorder applications IF CH 3 CH 4 30Hz and sync generation are crystal controlled for frequency accuracy and stability 4 5MHz SOUND SUB CARRIER Z COMPOSITE VIDEO OUTPUT 4 5MHz subcarrier modulated with 1KHz audio tone can be switched on to check sound and verify picture and sound Composite video output with variable 0 to 1V amplitude isolation into standard 750 impedance Calibrated 1 V with negative sync SPECIFICATIONS PATTERNS NTSC Color Bars White 75 or 100 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 scan Chroma Accuracy 5 and 5 units Raster Black Convergence Center dot 7 x 11 dots center cross 7 x 11 crosshatch Selectable interlaced or progressive scan RF OUTPUT Channels CH3 CH4 IF Frequenc
9. MHz CH 4 by the CH 4 CH 3 and IF RF switches 30Hz Jack Provides a 30Hz square wave TTL level output useful for troubleshooting video recorders COMPosite SYNC Jack Provides both horizontal and vertical sync pulses for external use such as monitors requiring separate composite sync or sync trigger for an oscilloscope Sync pulse is negative polarity Output impedance is 75Q level is TTL compatible 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 750 Level is TTL compatible 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 75Q level is TTL compatible B Jack Provides blue output signal for use with RGB monitors Output impedance is 43 and output level is switch selectable using the RGB TTL LOW switch CONTROLS AND INDICATORS CONT NTIS SRR NAR meeen cancan TP PEPEHRREHEVETPIRPEPIPPEPRERRIAEVERVERERIRRIEEERURERERERERERU Fig 4 Controls and Indicators 20 CONTROLS AND INDICATORS CONT 19 20 G Jack Provides green output signal for use with RGB monitors Output impedance isQ75 and output level is switch selectable using the RGB TTL LOW switch R Jack Provides red output signal for use with RGB mon
10. RT 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 blanking 12 interval begins with the first equalizing pulse which consists 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 vertical 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 is at the 40 IEEE units level and the narrow portion 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 timing relationship produces the interlace of Fields and 2 The NTSC color bars pattern generated by this instrument is interlaced per NTSC standards AMPLITUDE Refer to Fig 1 A standard NTSC composite video signal is 1 volt peak to peak from the tip of a sync pulse to 100 whit
11. ST POINT ON SMALL PCB 1 VR12 VR10 VR9 L4 SOUND SUBCARRIER TEST POINT Fig 8 Adjustment and Test Point Locations 35 MAINTENANCE CONT 3 Connect the Waveform Monitor and the Vectorscope to the COMPOSITE VIDEO jack terminated into 75 52 Set the Waveform Monitor response to FLAT and the sweep to 2H Set the variable amplitude control on the Waveform Monitor to the CAL position Set the sync to internal and turn on the DC restorer Color Subcarrier Adjustment Connect the frequency counter at the junction of R95 and pin 6 of the right hand side of R95 and adjust C4 for a reading of 3 579545MHz 3Hz on the frequency counter Sound Subcarrier Adjustment Press the 4 5MHz switch on the Generator Connect the frequency counter at the junction of R81 and pin 13 of IC18 the back lead of R81 and adjust L4 for a reading of 4 49MHz 10kHz on the frequency counter Release the 4 5 MHz switch on the NTSC Generator I F and RF Adjustments 1 Make sure that the CH 4 CH 3 switch is disengaged in the CH 3 position connect the frequency counter to the IF RF jack and adjust the core of L2 fully clockwise to the bottom or until the frequency counter reads below 61 245MHz Now adjust L2 counterclockwise until the frequency counter reads 61 250MHz 5KHz Turn the core an additional 1 2 turn counter clockwise The reading on the frequency counter should retrain stable 36 10 Press the CH 4 CH 3
12. computer and video monitors using standard 525 line 15 750KHz scan The inputs to these RGB monitors are separate digital signals for red green and blue and separate digital composite sync or separate digital vertical and horizontal sync The signal level at the RGB outputs is switch 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 for use with 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 recorders The switch selectable 4 5MHz sound sub carrier modulated by a 1KHz tone and is used to check the sound circuits and audio video isolation FEATURES RF OUTPUT NTSC COLOR BARS Standard 750 output modulated by composite video at Generates standard NTSC color bars pattern eight bars of 10mV rms on channel 3 channel 4 or 45 75MHz i f standard EIA colors at NTSC prescribed luminance and chrominance levels and phase SYNC PULSE OUTPUTS SELECTABLE COLOR All outputs can be used simultaneously for maximum flexibility Permits more complementary testing or Color can be switched on or off multiple independent usage of instrument CONVERGENCE PATTERNS RGB OUTPUTS Dots crosshatch center dot and center cross patterns for Digital red green and blue R
13. corresponding red green and blue inputs of the color monitor b If composite sync is required connect the COMPOSITE SYNC output of the Generator to the sync input of the monitor 26 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 the color monitor is equipped with 9 pin connector that mates with the RGB receptacle on the Generator connect it All necessary connections are made simultaneously 2 Select TTL or LOW level as appropriate for the monitor being tested 3 Select the desired pattern WAVEFORM MONITORING 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 waveform may be applied at various points in the equipment under test The waveform measured at the video detector of the unit under test may be compared 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 handy for such wave form comparison f Connect a coaxial cable from the COMPOSITE VIDEO output jack to the vertical input o
14. ding improper alignment and adjustment if the normal vectorscope pattern is known However since normal patterns vary considerably from one TV to another a library of normal chassis uses 90 or 105 angle of demodulation displays measured from various popular TV chassis in good working condition is desirable for reference Oscilloscope Adjust for equal X and Y gain spot at 45 Y Input Vertical X Input Horizontal X Input Horizontal COLOR BAR Move To Blue Gun SIGNAL 12498 NTSC GENERATOR Fig 5 Using a Conventional Oscilloscope Fig 6 Using a Conventional Oscilloscope as a Vectorscope as a Vectorscope step 1 set up step 2 set up 32 APPLICATIONS CONT Yellow Red Magenta Reference Fig 7 Typical Vectorscope Display of Demodulated Color Bars Pattern Viewed on Conventional Oscilloscope 33 MAINTENANCE WARNING The following instructions are for use by qualified service personnel only To avoid electrical shock do not perform servicing unless you are qualified to do so A shock hazard is present 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 to replace the fuse or calibrate the NTSC Generator the case must be removed To remove the case perfor
15. e 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 black threshold At 100 units the signal represents 100 THE NTSC COLOR VIDEO SIGNAL CONT FIELD 1 odd field Bottom of picture Top of picture Pattern Pattern Equalizing Vertical Equalizing pulse syne pulse pulse 3 lines 3 lines 3 lines Vertical blanking interval Fig 2A Compo site Video Signal Showing Vertical Blanking Interval Field 1 13 THE NTSC COLOR VIDEO SIGNAL CONT FIELD 2 even field IEEE Units I 100 90 80 4 70 60 50 40 30 20 gt 10 260 261 262 0 10 20 30 40 L Top of picture Pattern Bottom of picture Equalizing Vertical Equalizing 1 2 Line gt puise sync pulse pulse 3 lines 3 lines 3 lines Produces interlaced Vertical blanking interval scan Fig 2B Composite Video Signal Showing Vertical Blanking Interval Field 2 14 THE NTSC COLOR VIDEO SIGNAL CONT white Levels between 7 5 and 100 units produce various shadings of grey Even when a composite vid
16. en the IF RF switch is in the rf position disengaged and this switch is disengaged in the CH 3 position the output signal at the IF RF jack corresponds 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 the output signal at the IF RF jack corresponds to TV channel 4 67 25MHz When IF RF switch is in the IF position engaged this switch has no effect on the output 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 1 Vp p into 75Q 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 into 752 19 12 13 14 15 16 17 18 COMPOSITE VIDEO Jack Provides a video output for signal substitution directly into the video circuits of a television receiver and for testing video recorders IF RF Jack Provides approximately 10mV rms int amp 2 5f envelope modulated by composite video Output carrier frequency can be set to 45 75MHz IF 61 25MHz CH 3 or 67 25
17. eo signal is not at the 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 for 100 white There is also a specific relationship between the amplitude of the composite video signal and the percentage of modulation of an rf carrier A television signal uses negative modulation wherein the sync pulses 40 units produce the maximum peak to peak amplitude of the modulation envelope 100 modulation and white video 100 units produces the minimum amplitude of the modulation envelope 12 1 2 modulation This is very advantageous because the weakest signal condition where noise interference can most easily cause snow is also the white portion of the video There is adequate amplitude guard band so that peak white of 100 units does not reduce the modulation envelope to zero COLOR Refer to Fig 3 The color information is a composite video signal consists of three elements luminance hue and saturation Luminance or brightness perceived by the eye is represented by 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 to black 15 Hue is the element that distinguishes between colors red blue gree
18. 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 in an individual TV set apply the channel 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 in the distribution 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 color bars pattern applied should be six dots located within the six small boxes of the Vectorscope as shown in 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 vectorscope graticule 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 inputs to a good laboratory oscilloscope such as the B K Precision Model 2120 The resulting display is a vectorscope pattern as shown in Fig 7 The oscilloscope should be set up for vectorscope operation as follows 31 Select the NTSC BARS pattern and apply to the TV set under test Set up to the oscilloscope for X Y operation Adjust the position cont
19. f the oscilloscope Terminate into 75Q OPERATING INSTRUCTIONS CONT 2 Connect another cable from the COMP SYNC output jack to the external trigger input of the oscilloscope 3 Select the external triggering mode on the oscilloscope 4 sweep rate of about 10ps div is appropriate for viewing horizontal tines of composite video 2 ms div for viewing vertical fields and 5 ms div for viewing vertical frames The sweep vernier may be used for tine adjustment of the waveform display SIMULTANEOUS OUTPUTS For maximum flexibility all output jacks may be used simultaneously if desired This can be a valuable aid in many applications These outputs are summarized as follows 27 The COMPOSITE VIDEO output is continuously available when the instrument is operating The video component of the signal is dependent upon the selected 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 is negative going although the modulated 4 5MHz subcarrier can be added The COMP SYNC Vs Hs and 30 Hz are also continuously available The COMP SYNC output supplies negative polarity 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
20. ge 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 Exclusions This warranty does not apply in the event of misuse or abuse of the product or as a result of unauthorized alterations or repairs The warranty is void if the serial number is altered defaced or removed B amp K Precision 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 amp K Precision Corp 22820 Savi Ranch Parkway Yorba Linda CA 92887 www bkprecision com 714 921 9095 39 TEST INSTRUMENT SAFETY CONT 10 continued from inside front cover 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 plastic or wooden cabinet usually insulates the chassis to protect the customer but when the cabinet is removed for servicing there is great danger of serious electrical shock if the chassis is touched To prevent electrical shock always connect an isola
21. he center of the screen DOT and 7 X 11 switches engaged 7 horizontal rows by 11 vertical columns of dots RAST Switch Selects a black or blank raster pattern Sync and reference black are provided for a blemish free raster NTSC BARS Switch Selects NTSC Color Bar pattern COLOR OFF Switch Works in conjunction with NTSC BARS switch and selects color or monochrome black and white output When this switch is engaged the color subcarrier is switched off and the NTSC BARS pattern will be displayed as shades of grey When this switch is disengaged the color subcarrier is switched on and the NTSC BARS pattern will be displayed in color 4 5 MHz Switch Turns 4 5MHz subcarrier sound on and off When this switch is engaged a 4 5MHz sound carrier modulated by 9 10 11 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 signal IF RF Switch Sets modulated output signal at the IF RF output jack to rf or i f frequency When this switch 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 the signal at the IF RF jack is at rf signal frequency 61 25MHz for CH 3 or 67 25MHz for CH 4 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 Wh
22. he 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 general check of vertical and horizontal sync Center Dot Pattern Some technicians and engineers prefer to use a center dot for centering adjustment 29 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 low voltage conditions Some sets have a tendency toward more overscan than others It is desi
23. ible test signals for most RGB monitors using standard 525 line 15 750KHz horizontal OPERATING INSTRUCTIONS CONT scan It is not 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 provides signals 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 available at additional BNC connectors also on the front panel To simplify connections a 9 pin connector sub miniature D type is provided which mates with the 9 pin connector used on the most common RGB monitor configuration the connector is IBM PC compatible This duplicates the functions of the R G B Vs and Hs jacks in one connector so that all connections are made simultaneously with a single cable The procedure for using the RGB outputs is as follows 1 Connect the RGB outputs of the NTSC Generator to the inputs of the color monitor a Connect the R G and B outputs of the Generator to the
24. is usually present on some power input circuits such as the on off switch fuses power transformer etc any time the equipment is connected to an ac outlet even if the equipment is turned off Servicing of this unit should be performed only by qualified electronics technicians who are trained to work safely in the presence of high voltage Never work alone Someone should be nearby to render aid if necessary Training in CPR cardio pulmonary resuscitation first aid is highly recommended 40 BK CISION 22820 Savi Ranch Parkway Yorba Linda CA 92887 www bkprecision com 2006 B amp K Precision Corp Printed in USA PN 480 760 9 001 41
25. itors Output impedance is 75Q and output level is switch selectable using the RGB TTL LOW switch 21 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 OPERATING INSTRUCTIONS WARNING To prevent electrical shock observe the precautions listed in the TEST INSTRUMENT SAFETY section located on the inside front cover of this manual PRECAUTION AND TIPS 1 The most commonly encountered hazard in the use of this instrument is hot chassis equipment Always connect an isolation transformer such as the B amp K Precision Model TR 110 or 1604 Isolation Transformer or Model 1653A or 1655A AC Power Supply between the wall outlet and any hot chassis equipment under test See the TEST INSTRUMENT SAFETY section steps 7 and 8 for more information The and COMPOSITE VIDEO outputs of this NTSC Generator are rated to withstand voltages of 35 to 35 volts All other outputs are rated to withstand 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 voltage measurement first Also take care to prevent accidental contact
26. m the following steps 1 Turn the Generator upside down and remove the four screws 2 Liftthe bottom half of the case straight up FUSE REPLACEMENT If the fuse blows the pilot light will go out and the Generator will not operate The fuse should not open unless a problem has 34 developed in the unit Determine and correct the cause of the blown fuse then replace only with a 1 16A 250V slow blow fuse B K Precision Part No 198 303 0 062 The fuse is only accessible by removing the case For fuse location refer 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 e NTSC Vectorscope e Waveform Monitor e Frequency Counter with ppm time base accuracy B K Precision Model 1856D or equivalent 1 Before beginning calibration turn on the NTSC Generator and allow 15 minutes of warm up time 2 Engage COLOR OFF and BAST switches All other switches except POWER should be disengaged MAINTENANCE CONT COLOR VR201 SUBCARRIER TE
27. n 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 to create any hue A phase shift of 360 will produce every hue in the rainbow by changing the combination of red blue and green Saturation is the vividness of a hue which is determined 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 diagram Saturation is indicated by the length of the 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 the amplitude 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
28. n 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 in the form of a money order or credit card For the most current repair charges please visit www bkprecision com and click on service repair Return all merchandise to B amp K Precision Corp with pre paid shipping The flat rate repair charge for 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 amp K Precision Corp B amp K Precision 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 and description of problem 38 LIMITED ONE YEAR WARRANTY B amp 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 amp 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 form of a sales receipt To obtain warranty covera
29. neeness 5 SPECIFICATIONS rrt ere D 6 APPLICATIONS s oet ac uu cao eei coe oak LT DEFINITIONS OF TERMS 8 NTSC Color Staircase THE NTSC COLOR VIDEO SIGNAL 11 Convergence History hene ee rn RO e EO eed wll RF and LE Horizontal Sync prt exe eee et wll SYNC Vertical Sync 12 30Hz Output Amplitude 12 CCTV Applications Color 15 CATV Applications NISC Color Bars Signal tete 15 Applications CONTROLS AND INDICATORS 18 Vectorscope Measurements 21 OPERATING INSTRUCTIONS 22 MAINTENANCE 34 Precautions and Tips 4422 Case Removal e 34 Familiarization 1 22 Fuse Replacement 34 Initial Set Up XO d pr on 992 Calibration Coe cane petet welt utet eios 34 NTSC Standard Color Bar Pattern 24 Staircase Patteri 25 SERVICE INSTRUCTIONS aE EKET 38 Color Bars With 100 White 425 Staircase With 100 White 25 LIMITED ONE YEAR WARRANTY 39 Convergence Patterns 25 INTRODUCTION The B K PRECISION Model 1249B NTSC Generat
30. or is a versatile low cost precision television video signal generator It generates a variety of test signals and patterns 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 channel 3 channel d or the standard television i f frequency of 45 75MHz This provides the proper signal for injection at any point in the equipment The video patterns include standard NTSC color bats with standard 75 white or with 100 white staircase black raster and an assortment of convergence patterns An engineer or technician with a good knowledge of video circuits can use the 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 allowing 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 signal unlike that used during normal operation Separate RGB and sync outputs are available for use with most
31. p 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 Generator so that the black color bar the last one is 2 5 divisions wide on the Waveform Monitor If waveform jitters readjust VR2 slightly so that spacing is between 2 5 and 2 0 divisions 11 Press the LINE and 7 X 11 switches on the NTSC Generator Adjust VR3 so that the top horizontal line of the Waveform Monitor display 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 adjust until they are INSTRUMENT REPAIR SERVICE Because of the specialized skills and test equipment required for instrument repair and calibration many customers prefer to rely upon B amp K Precision for this service We maintain a network of B amp 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 warranty SERVICE INFORMATION Warranty Service 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 Warranty Service Retur
32. pecifications and information are subject to change without notice Please visit www bkprecision com for the most current product information DEFINITIONS OF TERMS BARS Pattern See NTSC Color Bars Back Porch The portion of a composite video signal between the trailing edge of the horizontal sync pulse and the end of the horizontal blanking pedestal The color burst occurs during the back porch interval Blanking Level The level of the front and back porches Zero IEEE units Burst See Color Burst CATV Cable Television Also used for Community Antenna Television CCTV Closed circuit television Chroma or Chrominance The color information contained in a video signal consisting of hue phase angle and saturation amplitude of the color subcamer Chroma Amplitude Amplitude of 3 58MHz color subcarrier Represents saturation Chroma Phase Angle Phase angle of 3 58MHz color subcarrier Represents hue Color Bars See NTSC Color Bars Color Burst 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 color burst 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 Composi
33. peed of lus div Adjust VRIO and 11 on the 1249B for minimum ripple on the bottom edge of the sync pulse Repeat until no further improvement is possible Color Adjustments Adjust the vertical and horizontal position 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 amplitude of 10 IRE Press the NTSC BARS switch and release the COLOR OFF switch on the Generator 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 the Vectorscope if necessary Adjust VR4 and VR9 on the Generator to bring the red vector into the small R box on the Vectorscope display Adjust VR6 to bring the blue vector into the small B box on the Vectorscope display Adjust VR5 to bring the green vector into the small G box on the Vectorscope display 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 37 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 readjust vectors if necessary 9 Release all of the pattern selection switches the four light colored pushbuttons by slightly depressing one of them With the Waveform Monitor swee
34. r on the left side of the screen should now be displayed STAIRCASE WITH 100 WHITE 1 Perform the INITIAL SET UP procedure 2 Release all of the pattern selection switches the four black pushbuttons by slightly depressing one of them Make sure that the 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 100 white CONVERGENCE PATTERNS 1 Perform the INITIAL SET UP procedure 2 Any of the four convergence patterns may be selected by 24 pressing the appropriate switch es as follows OPERATING INSTRUCTIONS CONT Only LINE switch engaged A single vertical and horizontal line intersecting at the center of the screen LINE and 7 X 11 switches engaged 7 horizontal lines and I vertical lines Only DOT switch engaged A single dot at the center of the screen DOT and 7 X 11 switches engaged 7 horizontal rows by I I vertical columns of dots 3 Convergence patterns use interlaced scan when the RGB TTL LOW switch is released This causes a slight jitter effect in the appearance of the pattern Progressive 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 signal unless interlaced scan is used All convergence patterns are monochrome On most se
35. rable to display 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 vertical and horizontal linearity Each square should be the same size which is a convenient reference for making linearity adjustments The crosshatch pattern is also used to check pincushion distortion which often appears at the outside ed es of large screen TV sets as bends in 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 be aided by the rf and i f outputs 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 composite video directly into the video section 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 normal operation is lost 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 ob
36. rols to center the dot on the screen with no signal InPut to the oscilloscope Connect the X and Y inputs of the oscilloscope to the red gun as shown in Fig 5 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 Leave the vertical Y input connected to the red gun but move the horizontal input to the blue gun as shown in Fig 6 A display similar to that shown in Fig 7 should 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 amplitude of display 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 The vectorscope pattern can be a valuable tool for troubleshooting color problems inclu
37. se shift occurs during each horizontal line This produces a gated rainbow pattern rather than specific phase controlled colors CONTROLS AND INDICATORS POWER Switch Turns power on and off 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 jacks R G and B BNC jacks and the RGB 9 pin D type connector is at 0 8V 0 2V level When this switch is engaged TTL position the pulses are at a TTL level This switch also selects interlaced or progressive scan for convergence patterns when the switch is released the convergence patterns use interlaced scan and then the switch is engaged the convergence patterns use progressive scan NOTE The DOT LINE RAST and NTSC BARS switches are mechanically interlocked se lection of a new pattern automatically releases the previous selection 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 available at the COMPOSITE VIDEO IR RF or RGB output jacks 3 CONVERGENCE Switches Select one of four available convergence patterns as follows 18 Only LINE switch engaged A single vertical and horizontal line intersecting at the center of the screen LINE and 7 X 11 switches engaged 7 horizontal lines and 11 vertical lines Only DOT switch engaged A single dot at t
38. serving the staircase pattern on an oscilloscope and checking whether the sync pulse amplitude remains at 0 53 compared 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 constant percentage of the total video amplitude 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 transition from field to field 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 inject the 30Hz signal from the Generator into the 30 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
39. switch on the NTSC Generator so that it is in the CH 4 position With the frequency counter still connected to the IF RF jack adjust the core of L3 fully clockwise to the bottom or until the frequency counter reads below 67 245MHz Now adjust L3 counterclockwise until the frequency counter reads 67 250MHz 5KHz Turn the core an additional 1 2 turn counter clockwise The reading on the frequency counter should remain stable Press the IF RF switch on the Generator so that it is in the IF position Adjust the core of LI fully clockwise to the bottom or until the frequency counter reads below 45 745MHz Now adjust L I counterclockwise until the frequency counter reads 45 750MHz 5 KHz Turn the core an additional 1 2 turn counter clockwise The reading on the frequency counter should remain stable Release the IF RF switch return to channel 4 rf operation The counter should now read 67 250MHz 5KHz If the reading is unstable repeat step 5 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 unstable repeat step 2 Sync Pulse Adjustment 1 Set the COMPOSITE VIDEO LEVEL control to CAL position and adjust VR8 for sync pulse amplitude of 40 IRE on the Waveform Monitor baseline on zero line MAINTENANCE CONT 2 Press the NTSC BARS switch and release the COLOR OFF switch Set the Waveform Monitor for a sweep s
40. tains sync and luminance but no color burst or chroma NTSC National Television Systems Committee Established the color television standards now in use in the U S A and many other nations 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 saturated hues of yellow cyan and magenta mixtures or two colors in 1 1 ratio without third color DEFINITIONS OF TERMS CONT Resolution See Horizontal Resolution and Vertical Resolution Saturation Vividness of color Degree to which a color 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 separation between blanking and black reference levels This instrument uses the NTSC standard 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 luminance Subcarrier See Color Subcarrier VCR Video cassette recorder VTR Video tape recorder In this manual the term VTR includes reel to reel and cassette type 10
41. te Video Signal The entire video signal consisting of blanking pulses sync pulses color burst and chrominance and luminance information Duty Cycle Percentage of cycle during which pulse is working A square wave has a 50 duty cycle Horizontal sync pulses have about 8 duty cycle about 5 5 pulse width at 63 5us pulse repetition period EIA Electronic Industries Association Equalizing Pulse A portion of the vertical blanking interval which is made up of blanking level and six pulses 8 duty cycle 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 DEFINITIONS OF TERMS 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 are vertically interlaced with Field 2 for 525 lines of resolution Frame A complete television picture consisting of two fields See Field Front Porch Blanking level pulse at end of line of horizontal scan before horizontal sync pulse 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
42. 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 monochrome television receiver 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 colors Red blue green yellow etc are hues White black and grey are not considered 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 100 100 white levels Chroma amplitude is the peak 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 to fall between the lines of Field 2 Also see Field Luminance The amount of light intensity perceived by the eye as brightness Luminance information is represented by the amplitude of the composite video signal Master antenna television Monochrome Black and white television signal Con
43. 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 then be adjusted to the same reference while connected into or removed from the system Virtually all equipment used in CCTV systems is designed around certain standard signal conditions at the input and output 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 75Q impedance and unbalanced line one side grounded The NTSC Generator has these characteristics which simplifies set up for testing troubleshooting and adjustment 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 can be used throughout a CATV network to test adjust or troubleshoot amplifiers cables and any other equipment APPLICATIONS CONT MATV APPLICATIONS Master antenna systems for hotels motels apartment buildings etc can be checked by applying the channel 3 or 4 rf output of the Generator to the input of the network or a branch of the network and
44. tion transformer between the ac outlet and any hot chassis equipment under test The B K Precision Model 1604A or TR 110 Isolation 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 equipment as hot chassis unless you are sure it has an isolated chassis or an earth ground chassis Use of an isolation transformer has no disadvantage even if it is not required In addition to the hot chassis shock hazard mentioned in Item 7 severe damage to test instruments or the equipment being tested is probable from connecting a cable between the NTSC Generator and any hot chassis equipment unless an isolation transformer is used The antenna terminals of a hot chassis set should already be isolated from the chassis unless defective and the isolation transformer may not be required For connection to any other point an isolation transformer is needed 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 oscilloscope Connection to higher voltage may damage the equipment When testing any ac powered equipment remember that ac line voltage
45. troubleshooting APPLICATIONS NTSC COLOR BARS Versatility The NTSC color bars pattern is the basic pattern used for most testing troubleshooting and adjustments in video equipment It is one of the most valuable and versatile color patterns ever devised The NTSC color bars pattern is very effective for adjusting any type of consumer or industrial color video equipment for maximum performance For troubleshooting and servicing analysis 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 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 and magenta help define problems wherein 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 chroma or luminance related Video Recorders The NTSC color bars pattern is virtually a necessity for video recorder servicing This includes video cassette recorders and video disc players 28 Most manufacturers specify an NTSC color bar input signal in their literature Adjustment procedures are usually based upon an NTSC color bar input and the waveforms shown at
46. ts the entire 7 X 11 pattern 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 and 10 vertical lines or dots BLACK RASTER PATTERN 1 Perform the INITIAL SET UP procedure 25 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 should not be completely 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 adjusted receiver the sound trap should prevent 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 herring bone pattern will appear on the screen To check the audio circuitry the 4 5MHz switch should be engaged when any pattern is selected The 4 5MHz subcarrier is modulated by an audio tone approximately IKHZz that can be used to troubleshoot 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 monitors are often used with computers having color graphic display capability etc The Model 1249B will provide compat
47. various points on the schematic diagram are those obtained with an NTSC color bar input Some manufacturers provide field and factory procedures in their literature 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 difference between the video played back from the VCR and an NTSC color bars pattern applied directly to the monitor Luminance and Chroma Balance 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 Waveforms APPLICATIONS CONT may be exam fined throughout the VCR for proper 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 t
48. ximum amplitude with negative polarity sync Clockwise rotation reduces level and the center of rotation is minimum level Rotation past the center reverses the polarity of the signal to positive sync and further clockwise rotation increases signal level Maximum clockwise rotation is approximately 1Vp p level although it is uncalibrated OPERATING INSTRUCTIONS CONT 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 may now be selected NTSC STANDARD COLOR BAR PATTERN 1 Perform the INITIAL SET UP procedure 2 Press the NTSC BARS switch Be sure that the COLOR OFF and 4 5MHz switches are released 3 NTSC Color Bar pattern should now be displayed on the screen STAIRCASE PATTERN 1 Perform the INITIAL SET UP procedure 2 Press the NTSC BARS switch and the COLOR OFF switches 3 A monochrome bars staircase display with progressively darker shades of grey should now be displayed with the lightest baron the left side of the screen and the darkest on the right side of screen on the screen COLOR BARS WITH 100 WHITE 1 Perform the INITIAL SET UP procedure 2 3 Release all of the pattern selection switches the four black pushbuttons by slightly depressing one of them Make sure that the COLOR OFF switch is disengaged A color bars pattern with 100 white color ba
49. y 61 25 67 25 45 75MHz 0 008MHz Level 10mV rms minimum into 75 ohms Impedance 75 ohms Stability 50 ppm VIDEO OUTPUT Polarity Negative and positive sync available Amplitude Variable 0 to 1 into 75 ohms Calibrated available with negative sync Impedance 75 ohms RGB OUTPUTS BNC and D Type Sub Miniature Connectors Patterns Convergence and color bars Levels TTL level and low level 0 8 0 2 switch selectable Impedance 75 ohms SPECIFICATIONS CONT SOUND SUBCARRIER 4 5MHz 0 2 modulated by approximately 1 KHz audio tone switch selectable 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 TTL level positive polarity sync Vertical TTL level positive polarity sync Impedance 75 ohms 30 Hz OUTPUT Level TTL level square wave Impedance 75 ohms COLOR SUBCARRIER NTSC signal 3 579545MHz 50Hz adaptable to PAL M MISCELLANEOUS Power Requirements 105 to 130VAC 60Hz 8 Watts Operating Temperature 0 to 50 C Dimensions 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 Weight 2 8 Ibs 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 Cable part number 539 123 0 000 NOTE S
50. your area Set the CH 4 CH 3 switch on the NTSC Generator to the same channel that was selected on the equipment under test Patterns may now be selected I F Output 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 b Connect a probe to the IF RF output jack of the NTSC Generator Set the RE IF switch on the Generator to the IF position engaged 23 6 d The probe may be used to inject the 45 75MHz i f signal at the desired point Patterns may now be selected 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 Connect a coaxial cable or probe from the COMPOSITE VIDEO jack of the Generator to the desired point in the equipment under test Adjust the COMPOSITE VIDEO LEVEL control to obtain the desired signal level and sync polarity at the output jack Fully counterclockwise rotation gives ma
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