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INSTRUCTION

MANUAL

Model 1249B

NTSC GENERATOR

Содержание 1249B

Страница 1: ...INSTRUCTION MANUAL Model 1249B NTSC GENERATOR ...

Страница 2: ...when necessary Turn off equipment while making test connections in high voltage circuits Discharge high voltage capacitors after removing power 3 If possible familiarize yourself with the equipment being tested and the location of its high voltage points However remember that high voltage may appear at unexpected points in defective equipment 4 Use an insulated floor material or a large insulated ...

Страница 3: ... Up 22 NTSC Standard Color Bar Pattern 24 Staircase Pattern 25 Color Bars With 100 White 25 Staircase With 100 White 25 Convergence Patterns 25 Page Black Raster Pattern 25 4 5MHz Subcarrier Use 25 RGB Output 25 Waveform Monitoring 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...

Страница 4: ...em 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 ar...

Страница 5: ...ed 1V p p with negative sync RF OUTPUT Standard 75Ω output modulated by composite video at 10mV rms on channel 3 channel 4 or 45 75MHz i f SYNC PULSE OUTPUTS All outputs can be used simultaneously for maximum flexibility Permits more complementary testing or multiple independent usage of instrument RGB OUTPUTS Digital red green and blue RGB signals for computer and video monitors with standard 525...

Страница 6: ... dots center cross 7 x 11 crosshatch Selectable interlaced or progressive scan RF OUTPUT Channels CH3 CH4 IF Frequency 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 1V p p into 75 ohms Calibrated 1V p p available with negative sync Impedance 75 ohms RGB OUTPUTS ...

Страница 7: ...sive 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...

Страница 8: ...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 Composite Video Signal The entir...

Страница 9: ...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 leve...

Страница 10: ...ideo tape recorder In this manual the term VTR includes reel to reel and cassette 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 within this interval Vertical Resolution Smallest increment of a television ...

Страница 11: ...orizontal 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 ar...

Страница 12: ...ertical deflection circuit so the electron beam will return to the top of the screen before video scan resumes The vertical blanking 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 pu...

Страница 13: ...13 THE NTSC COLOR VIDEO SIGNAL CONT Fig 2A Compo site Video Signal Showing Vertical Blanking Interval Field 1 ...

Страница 14: ...14 THE NTSC COLOR VIDEO SIGNAL CONT Fig 2B Composite Video Signal Showing Vertical Blanking Interval Field 2 ...

Страница 15: ...inguishes 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 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...

Страница 16: ...16 THE NTSC COLOR VIDEO SIGNAL CONT Fig 3 Elements of Color Television Signal ...

Страница 17: ... 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 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 nor...

Страница 18: ...lable at the COMPOSITE VIDEO IR RF or RGB output jacks 3 CONVERGENCE Switches Select one of four available convergence patterns as follows 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 the center of the screen DOT and 7 X 11 swi...

Страница 19: ...rated 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 1Vp p into 75Ω 12 COMPOSITE VIDEO Jack Provides a video output for signal substitution directly into the video circuits of a tele...

Страница 20: ...20 CONTROLS AND INDICATORS CONT Fig 4 Controls and Indicators ...

Страница 21: ... Jack Provides red output signal for use with RGB monitors Output impedance is 75Ω and output level is switch selectable 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 ...

Страница 22: ... 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 with high voltage points 3 All outputs have a source impedance of 75Ω Therefore 75Ω coaxial cable RG 59 U is recommended for interconnecting cables FAMILIARIZATION To familiarize yourself with t...

Страница 23: ...erator to the IF position engaged c The probe may be used to inject the 45 75MHz i f signal at the desired point d Patterns may now be 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 b...

Страница 24: ... the darkest on the right side of screen on the screen COLOR BARS 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 disengaged 3 A color bars pattern with 100 white color bar on the left side of the screen should now be displayed STAIRCASE WITH 10...

Страница 25: ...e 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...

Страница 26: ...G and B outputs of the Generator to the 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 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...

Страница 27: ...e outputs are summarized as follows 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 COMPOSI...

Страница 28: ...ette recorders and video disc players 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 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 proced...

Страница 29: ...ring 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 low voltage conditions Some sets have a tendency toward more overscan than others It is desirable to display at lea...

Страница 30: ...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 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 wo...

Страница 31: ...nals 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 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 pos...

Страница 32: ...dulation 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 considerably from one TV to another a library of normal displays measured from various popular TV chassis in good working condition is desirable for reference Fig 5 Using a Conventional...

Страница 33: ...33 APPLICATIONS CONT Fig 7 Typical Vectorscope Display of Demodulated Color Bars Pattern Viewed on Conventional Oscilloscope ...

Страница 34: ... 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 calibr...

Страница 35: ...35 MAINTENANCE CONT R7 Fig 8 Adjustment and Test Point Locations ...

Страница 36: ...ockwise The reading on the frequency counter should retrain stable 3 Press the CH 4 CH 3 switch on the NTSC Generator so that it is in the CH 4 position 4 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 5 Now adjust L3 counterclockwise until the frequency counter reads 67 250MHz 5K...

Страница 37: ...m 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 sweep switch still set on 2H adjust VR20I on the Generator for a white level of 100 IRE ...

Страница 38: ...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 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 Serv...

Страница 39: ...ation 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 K Precision Corp shall not be liable for any consequential damages including without limitation damages resulting fr...

Страница 40: ...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 9 Capacitive coupled outputs of the Model 12...

Страница 41: ...41 22820 Savi Ranch Parkway Yorba Linda CA 92887 www bkprecision com 2006 B K Precision Corp Printed in USA PN 480 760 9 001 ...

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