INSTRUCTION MANUAL Model 1249B 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.
TABLE OF CONTENTS Page Page Black Raster Pattern .......................................................... 25 4.5MHz Subcarrier Use ........................................................... 25 RGB Output ............................................................................. 25 Waveform Monitoring ............................................................. 26 Simultaneous Outputs .............................................................. 27 TEST INSTRUMENT SAFETY .........................
INTRODUCTION 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. The 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 patterns for comprehensive testing, servicing, and adjustment of video and television equipment.
FEATURES RF OUTPUT Standard 75Ω output modulated by composite video at 10mV rms on channel 3, channel 4, or 45.75MHz i-f. NTSC COLOR BARS Generates standard NTSC color bars pattern (eight bars of standard EIA colors) at NTSC prescribed luminance and chrominance levels and phase. SYNC PULSE OUTPUTS All outputs can be used simultaneously for maximum flexibility. Permits more complementary testing or multiple independent usage of instrument. SELECTABLE COLOR Color can be switched on or off.
SPECIFICATIONS PATTERNS Impedance: 75 ohms. 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 scan. Chroma Accuracy Stability: 50 ppm. VIDEO OUTPUT Polarity : Negative and positive sync available. : ±5° and ±5 EEE units. Amplitude: Raster: Variable 0 to ±1V p-p into 75 ohms.
SPECIFICATIONS (CONT.) COLOR SUBCARRIER NTSC signal: 3.579545MHz (±50Hz) (adaptable to PAL-M). SOUND SUBCARRIER 4.5MHz ±0.2% modulated by approximately 1KHz audio tone, switch selectable. MISCELLANEOUS Power Requirements: 105 to 130VAC, 60Hz. 8 Watts. Operating Temperature: 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). 0° to +50°C.
DEFINITIONS OF TERMS 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. 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.
DEFINITIONS OF TERMS (CONT.) Frame. A complete television picture, consisting of two fields. See "Field". 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.
DEFINITIONS OF TERMS (CONT.) Resolution. See "Horizontal Resolution" and "Vertical Resolution". 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. Saturation. Vividness of color. Degree to which a color is not diluted by white light. Highly saturated color is very vivid.
THE NTSC COLOR VIDEO SIGNAL 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 3.579545MHz subcarrier contains the color information.
THE NTSC COLOR 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.
THE NTSC COLOR VIDEO SIGNAL (CONT.) Fig. 2A. Compo site Video Signal Showing Vertical Blanking Interval (Field 1).
THE NTSC COLOR VIDEO SIGNAL (CONT.) Fig. 2B.
THE NTSC COLOR VIDEO SIGNAL (CONT.) 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 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.
THE NTSC COLOR VIDEO SIGNAL (CONT.) Fig. 3.
THE NTSC COLOR VIDEO SIGNAL (CONT.) 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° phase shift occurs during each horizontal line. This produces a gated rainbow pattern rather than specific, phase controlled colors.
CONTROLS AND INDICATORS 1. POWER Switch. Turns power on and off. Only LINE switch engaged: 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 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.
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. 12. COMPOSITE VIDEO Jack. Provides a video output for signal substitution directly into the video circuits of a television receiver and for testing video recorders. 9. IF/RF Switch. Sets modulated output signal (at the IF/RF output jack) to rf or i-f frequency.
CONTROLS AND INDICATORS (CONT.) Fig. 4.
CONTROLS AND INDICATORS (CONT.) 19. G Jack. Provides green output signal for use with RGB monitors. Output impedance isΩ75 and output level is switch selectable (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 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.
OPERATING INSTRUCTIONS 3. WARNING To prevent electrical shock, observe the precautions listed in the TEST INSTRUMENT SAFETY section, located on the inside front cover of this manual. 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.
OPERATING INSTRUCTIONS (CONT.) 4. c. The probe may be used to inject the 45.75MHz i-f signal at the desired point. d. Patterns may now be selected. 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. b. c. Connect a coaxial cable from the IF/RF output jack of the NTSC Generator to the antenna terminals. The 75Ω input point is desired, or use 75Ω to 300Ω coupler.
OPERATING INSTRUCTIONS (CONT.) c. d. 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. Patterns may now be selected. 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.
OPERATING INSTRUCTIONS (CONT.) Only LINE switch engaged: A single vertical and horizontal line intersecting at the center of the screen. 2. Press the RAST switch. The COLOR OFF switch should have no effect on the display regardless of whether it is engaged or disengaged. LINE and 7 X 11 switches engaged: 3. The screen should not be completely black (black raster or black-burst). 7 horizontal lines and I I vertical lines. Only DOT switch engaged: 4.
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.
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. A sweep rate of about 10µs/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.
APPLICATIONS 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.
APPLICATIONS (CONT.) 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 least a 7 x 9 dot pattern.
APPLICATIONS (CONT.) SYNC 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. The NTSC color bars and staircase pattern include NTSC sync pulses, the same type as those produced by a broadcast station.
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 examining the pattern obtained on channel 3 or 4 directly from the screen of each TV set.
APPLICATIONS (CONT.) d. e. 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. 7. Display shape will vary depending upon whether TV chassis uses 90° or 105° angle of demodulation. Fig. 5. Using a Conventional Oscilloscope as a Vectorscope, step 1 (set-up).
APPLICATIONS CONT.) Fig. 7. Typical Vectorscope Display of Demodulated Color Bars Pattern Viewed on Conventional Oscilloscope.
MAINTENANCE W ARNI N G 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. 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.
MAINTENANCE (CONT.) R7 Fig. 8. Adjustment and Test Point Locations.
MAINTENANCE (CONT.) 3. Connect the Waveform Monitor and the Vectorscope to the COMPOSITE VIDEO jack (terminated into 75 S2). 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 1. Connect the frequency counter at the junction of R95 and pin 6 of IC1 (the right hand side of R95) and adjust C4 for a reading of 3.
MAINTENANCE (CONT.) 2. Press the NTSC BARS switch and release the COLOR OFF switch. Set the Waveform Monitor 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 further improvement is possible. Color Adjustments 1. 2. 3. 4.
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: 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.
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 form of a sales receipt. To obtain warranty coverage in the U.S.A.
TEST INSTRUMENT SAFETY (CONT.) (continued from inside front cover) 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.
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