Chapter 1 Applications of Television 1-1 a. b. c.
A picture tube is similar to a loudspeaker. The two Baseband signals are video and audio. Video signals have a higher frequency compared to audio signals.
a. b. c. d.
The vidicon is a camera tube. The chroma subcarrier signal frequency is 3.58 MHz. The frequency in TV channel 2 broadcast is 54-60 MHz. The maximum beam current in the picture tube is for white in the picture.
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1-3 What are the abbreviations for the following types of equipment? a. Special-effects generator. SEG b. Studio-transmitter link. STL c. Electronic newsgathering. ENG 1-4 a. b.
Rotating heads increase the writing writing speed for video video recording. T The type C video recorder produces produces two slanted tracks tracks on the tape for each picture field. field. T
a. b. c.
TV channel channel receiver receiver set set for cable cable input input in a 36-channel 36-channel system system is 3,4 or 6. The head end feed the trunk. The line drop is at the subscriber branch.
a. b. c.
Facsimile is an example of slow-scan TV. Facsimile pictures generate low video frequency, compared with with those those for TV broadcasting. broadcasting. T An infrared infrared vidicon camera tube tube can show difference difference of temperature in the scene. T
a. b.
The channel 3 signal is a modulated RF signal. The maximum maximum RF signal at the antenna input terminals terminals from from a video game is is 3 mV.
c. d.
A modern unit unit has two functions: modulation and demodulation. T The ASCII ASCII code uses 128 combinations of7 bits bits for alphanumeric information. T
a. b. c.
The Flyback high voltage depends on horizontal scanning. AFC is used for horizontal synchronization. Channel 14 is a UHF channel.
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Chapter 2 The Television Picture 2-1 a. b. c.
One picture element is a pixel. A still picture has many pixels, T The position of a picture element is important in the reproduction.
a. b.
How many complete picture frames are scanned in 1 sec? 30 How many scanning lines are there In one frame? 525
a. b.
Motion is shown shown by a rapid succession of still pictures. T Flicker results when the screen is m ade alternately bright and dark.
a. b.
How many scanning fields are there in one one picture picture frame? 2 How many fields are scanned in one second? 60
a. b. c.
What is the horizontal scanning frequency in hertz? 15750 Hz. What is the time for scanning scanning one horizontal line in one second? second? 63.5 s. What is the vertical field-scanning frequency, in hertz? 60 Hz.
a. b.
What is the frequency frequency of horizontal synchronizing synchronizing pulses for every line, in in hertz? 15,750 Hz. What is the frequency frequency of vertical synchronizing synchronizing pulses for every every field? field? 60 Hz
a. b.
The Y luminance is for black-and-white black-and-white picture information. The chrominance signal for color is 3.58 MHz.
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c.
The chrominance signal includes red, green, and blue picture information.
a. b.
More video signal increases the contrast. The average screen illumination is its brightness.
a. b. c.
What is the width of TV broadcast channel? 6 MHz What is the intercarrier sound frequency? 4.5 MHz What is the maximum frequency deviation for the FM sound signal? 25 kHz
a. b. c.
What is the aspect ration for a TV picture? 4:3 The picture carrier signal is AM. The sound carrier signal is FM
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Chapter 3 Television Cameras 3-1 a. b. c.
The lens inverts the optical image on the faceplate of the camera tube. The composite video signal includes the camera signal, signal and blanking. The standard composite video signal from a camera is 1 Vp-p with negative sync.
a. b.
The diameter of the vidicon image plate is about 2/3, 1 or 1.2 inch. The plumbicon camera tube uses a lead-oxide target plate.
a. b. c. d.
The signal variations are produced by the target plate. The photoconductive layer have less resistance with increasing light. The dark current is checked when the lens cap is on. Image lag is a problem of the target plate.
a. b.
The target of the Saticon is not constructed in the same way as that of the Plumbicon. The use of bias lighting in Saticon reduces the image lag.
a. b.
The typical target voltage is more than 50 V. Beam alignment is similar to centering of the electron beam.
a. b. c. d.
Dichroic mirrors are more efficient than optical filters for separating red, green, and blue light. Dynamic Shading corrects for optical effects in the light splitter. Static shading corrects for non-uniform dark currents. White balance is necessary for color cameras.
a. b. c.
The gamma required for the camera tube is 0.4545. Gamma correction is more important for color TV. White is stretched by the picture tube.
a.
The horizontal scanning with and the linearity affect the color video signal in single-tube color pick-up.
a. b. c. d.
The SEG can also be used as s production switcher. CVBS means composite video, burst and sync. Commercial movie film is run at 24 film frames per second for TV. Gen-Lock is used to synchronize multiple cameras.
a. b. c.
A low f stop rating allow more light. The depth-of-field is improved with a higher f stop. To how many lux units is the illumination of 3 fc approximately equal? 30
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Chapter 4 Picture Tubes 4-1 a. b. c.
What is the diagonal screen size for 19CP4 picture tube? 19 To what deflection angle does a maximum deflection angle of 45 either side of center correspond? 90 The usual heater voltage for picture tubes is 6.3V.
4-2 a. b.
Typical anode voltage for a 25-in color picture tube is 30 kV. Typical anode capacitance is 2000 pF.
a. b. c.
The phosphor numbers for monochrome is P4 and for color picture tubes is P22. Aluminized tubes do not need an ion-trap. What is the color of the P1 phosphor? Green
a. b. c.
Control Grid is the most negative electron gun. Ultor or Anode is the most positive electron gun. Most of the electrons in the beam flow out of the anode terminal.
a. b. c.
The crossover point for focusing is formed by the first electron lens. A G3 voltage of 200V is used for low-voltage focus method. For most color picture tubes, the G3 focus voltage is an adjustable value of several kilovolts.
a. b. c. d.
The small magnets embedded in the yoke housing correct for pincushion distortion. The coils above and below the electron are for H scanning. Two permanent-magnet rigs just behind the yoke are used for centering the beam in monochrome receivers. Neck shadow result when the deflection yoke is too far back.
a. b.
Separation of the beams for the red, green and blue colors is accomplished by the shadow mask. In-line guns are easier than the delta guns in making the convergence adjustments.
a. b.
A shadow mask has about 300,000 holes. The holes in the shadow mask is conical in shape to prevent secondary emission.
a. b.
Ambient room lighting makes black on the screen appear lighter. Opaque phosphor masking improves contrast by making black appear darker.
a. b.
A TV projection picture shows less detail than the image on a direct-view picture tube. The typical anode voltage for projection tubes is 30 to 80 kV.
a. b.
When a picture tube is being discharged, the ground end of the clip lead should be connected first. Hold-down circuits limit the amount of color saturation.
a.
Weak emission from the cathode of the electron gun causes saturation limiting, with the picture appearing silvery gray where it should appear white. No picture, with a bright, blank raster and no control of brightness, may indicate a short circuit between the cathode and the control grid in the picture tube. A yellowish brown monochrome picture slowly balancing to a neutral gray scale indicates weak emission in the blue gun.
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b. c.
Chapter 5 Set up Adjustments for the Color Picture Tubes 5-1 a. b. c.
The color purity magnet serves as a centering magnet. The color purity and beam landing adjustments are the same. The color purity is adjusted for the raster, one color at a time. T
a. b. c.
Degaussing should be done before the color purity adjustments. The degaussing is done 60 Hz ac. The ADG circuit have a high current when the receiver is first turned on.
a. b. c.
A solid red raster is a check for good color purity. Small white dots in the picture are used for convergence adjustments. Color fringing on the edges of the picture is a sign of misconvergence.
a. b.
Static convergence is done for the center of the screen. Permanent magnets are used for static convergence.
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a.
The basic waveform for dynamic convergence is the parabola or a half sine wave.
a. b.
Pincushion magnets are used for monochrome picture tubes. The abbreviation TB (Top to Bottom) is vertical pincushion correction.
a. b. c.
Typical dc grid bias for 19-in picture tube is –60 V. Typical ac signal drive for a 19-in picture tube is 140 Vp-p. The brightness control vary the dc bias for the picture tube.
a. b. c. d.
The R, G, and B screen-grid adjustment is set for visual cutoff. The R, G, and B video drive controls are set for white. The background controls are for dc bias. The G2 master screen control varies the dc voltage video signal.
a.
The color purity is adjusted before the dynamic convergence.
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Chapter 6 Scanning and Synchronizing 6-1 a. b.
Retrace is faster than trace. V retrace takes more time than H trace.
a. b.
Interlace scanning require odd number of horizontal lines. How many horizontal lines are in an odd or even field? 262 and ½
a. b. c.
How many scanning H lines are there in a complete frame? 21 How many H lines are there in each field? 10 and ½ How many H lines are there in each V retrace? 3
a. b.
Flicker is caused by the changes between black and white. Increasing the vertical blanking rate prevents flicker.
a. b. c.
All synchronizing pulses have the same amplitude. The frequency of equalizing pulses is 60 Hz. The H sync pulses have a higher frequency than the V sync pulses.
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Chapter 7 Video Signal Analysis 7-1 a.
What are the 3 parts of the composite video signal? Camera signal, H sync and H blanking.
a. b. c.
IRE of Sync: 40 Black set up: 7.5 The camera signal: 92.5
a. b. c.
Width of H blanking pulse? 10.2 s. Visible H trace? 53.5 s. Width of H sync pulse? 5 s.
a. b. c.
V sync: 3H lines wide V blanking 21H lines wide Equalizing: 31,500 Hz
a.
Typical video signal voltage for the picture tube is 100 V with negative polarity.
a.
Sync polarity is negative.
a. b.
Maximum number of pixels for each horizontal line is 426. For the total picture area, it is 144,000.
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7-8 a. b.
The average dc level is close to the blanking level for a dark scene. The picture tube reproduce black with zero beam current.
a. b.
Gamma affects the contrast. Picture tubes have a gamma greater than 1.
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Chapter 8 Color Television Circuits and Signals 8-1 a.
What are the phosphor colors for the tricolor tube? RGB
a. b. c.
What color when added to yellow, will produce white? Blue What color is the complement of blue? Yellow Green, when added to blue, produces cyan.
a. b. c.
Red is the hue of the color. Pink is different from red in saturation. Red has a low luminance.
a. b. c.
The input to the matrix includes R, G and B video signals. The output to the matrix includes Y luminance and two color-mixture signals. The Y signal has 59 percent G video.
a. b. c. d. e.
Name the three output of the matrix. Y, I and Q The two inputs to the modulator are I and Osc. What is the phase angle for the Q modulator? 90 Which stage has inputs of Y + C signals? Multiplexer Which resistor has I and Q modulation? Rc
a. b. c.
What is the frequency of the chroma bandpass filter? 3.58 MHz. Name the two inputs to the R – Y demodulator? C and Osc (r-y) What is the phase angle between B-Y and R-Y? 90
a. b. c. d. e.
What is the value of the Y voltage for the following bars? White: 1.00 Red: 0.30 Green: 0.59 Blue: 0.11 Yellow: 0.89
a. b. c. d.
The hue of the B-Y video signal is mainly blue. The R-Y phase is in quadrature with B-Y. The B-Y and R-Y can be combines to form G-Y. The B-Y is 180 out of phase with the color sync burst.
a. b.
What is the frequency of the individual cycles in the color sync burst? 3.58 MHz What is the repetition rate for the complete group of the color sync burst? 15,750 Hz
a. b. c.
What is the hue of the color sync burst? Yellow-Green What is the phase difference between the color sync burst and the B-Y signal? 180 What is the phase angle of the R-Y video? 90
a. b. c.
Calculate the values for the yellow and blue bars in the following: Y signal: 0.89 and 0.11 Q signal: -0.39 and 0.31 C signal: 0.45 and 0.45
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8-12 a.
Compared with 100 percent saturation, a desaturated color have more luminance for the Y signal and less chrominance for the C signal.
a. b.
What are the practical Baseband frequencies for the color video signal? 0.5MHz Large areas of picture information is easier to show in color.
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8-14 a. b. c. d.
What is the exact horizontal line-scanning frequency for color TV? 15,734.27 MHz What is the exact vertical field-scanning frequency for color TV? 59.94 Hz What is the exact color subcarrier? 3.579545 MHz Which frequency is made exactly an odd multiple of H /2? C signal.
a.
The PAL system alternates the phase of the color signal in successive lines.
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Chapter 9 Video Test Signals 9-1 a. b. c. d.
In the test pattern, the H resolution measures the vertical lines. How many horizontal details can be resolved with 300-line resolution? 400. How many gray-scale steps are in the EIA test pattern? 10. Smooth diagonal lines show good interlacing.
a. b. c.
The line in the vertical wedges indicates horizontal resolution. How many actual horizontal details correspond to the resolution of 210 lines? 280. What video frequency corresponds to 240 lines of horizontal resolution? 3Mhz.
a.
Excessive gain at 3.75 Mhz cause ringing.
a. b.
Monoscope is a special type camera tube with a fixed image of a test pattern printed on the target. A fixed image is engraved on the target plate of the Monoscope. T.
a. b. c.
A ball chart is used with crosshatched pattern. The ball chart test is for the camera. The maximum permissible nonlinearity for broadcast cameras is 2 percent.
a. b.
Which peak C value matches 100 percent white in amplitude? Cyan. A vectorscope is an oscilloscope.
a. b.
How many IRE units is the white window signal? 100. How many microseconds is the width of the window signal? 26.25 s.
a. b. c. d.
A T sine-squared pulse have an HAD of one picture element. A 2T sine-squared pulse has an HAD of 0.25 s. A 2T sine-squared pulse has no high frequency components above 4 Mhz. A modulated 12.5T pulse has a peak amplitude higher than the flat part of the window signal. This means that the gain for 3.58 Mhz is too high.
a. b.
How many H lines wide is the vertical sync pulse? 3. What is the count for the H line just after all the equalizing pulses? Line 10.
a.
What is the p-p value for a 3.58 Mhz signal on each step of the modulated stair-step in IRE units? 7.5.
a. b. c.
Which two lines in V blanking are used for VITS? 17 and 18. What line is used for the mulitiburst test signal? 17. What is the highest test frequency in the multiburst? 4.2 Mhz.
a. b. c.
Name the test signals transmitted in the vertical blanking interval. VIRS and VITS. VIRS is transmitted on line 19. Which test signal has the reference values for the chroma phase and amplitude? VIRS.
a. b. c.
The SMPTE code uses lines 12, 13 and 14 in the vertical blanking time. SMPTE – Society of Motion Pictures and Television Engineers SMPTE time code is used to identify the program material, time of day, frame number, and other production information. Videotext – when data are distributed in the form of video signals
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d.
e. f.
Teletext – method of using TV broadcast signal. It is the system of transmitting communications signals in the vertical blanking interval, by either broadcast or cable television. Visual captions for the TV picture can be encoded in the V blanking time. T
CHAPTER 10 Video Tape Recorders and Disk Players 10-1 a. b. c. d.
The range of 30 to 40 Hz is 3 octaves. T Frequency modulation is used for video signals. In video recording, both the tape and the head gap are in motion. T The VCR and TV receiver must be operating on the same channel in order to record. F
a. b. c.
Which is nonmagnetic, the head core, the gap or the tape? Gap The high-frequency response improved with a thinner head gap. There are 2 octaves in a range of 4:1 in frequencies equal.
a. b. c.
The frequency range of the recorded FM signal is less than 3 octaves. For video recording FM is better than AM. T In the VHS and Betamax systems, the luminance signal is modulated for recording. T
a. b. c. d.
The luminance is recorded as an FM signal. A 700 kHz is a color-under. In VHS system, 3.58 MHz corresponds to 629 kHz color under frequency. The highest frequency to be played back in a typical VCR is 5-6 MHz.
a. b. c. d.
One TV field does a slant track record in one pass. The angle of wrap that the tape makes around the scanner head slightly is more than 180 . Head switching takes place at the bottom of the TV picture. Increasing the drum diameter increases the writing speed.
a. b. c. d.
The timing reference for the scanner servo in the recording is the V sync divided by 2. T A tone generator on the scanner shaft indicates the frequency of rotation. T A pickup coil next to a magnet on the scanner shaft indicates the position of the reference video head. T A sample-and-hold circuit is used as a timing comparator. T
a. b. c. d.
The control and audio are the two stationary recording heads. Tape speed is controlled by the capstan. The poor tracking of the video heads causes snow in the picture. The exact frequency of the CTL pulses is 29.97Hz.
a. b. c. d.
In the zero guard-band system, at 6 or 7 is the angle in each head canted. The canted azimuth angle work better for luminance signals. The time delay of the comb filter is 1H or 63.5 s. th The frequency that is the 455 harmonic of H/2 is 3.579545 MHz.
a. b. c.
The supply reel of tape in the video cassette is at the left side. T The audio track can be erased, but the video tracks cannot. F The audio and the control heads rotate in the same direction as the scanner. F
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10-10 a. b. c.
The CED system is based on variations in capacitance. T The VLD system requires a laser light beam. Videodisk machines are generally used for playback but not for recording. T
10-11 a. b. c.
A laser source produces coherent light. T The recorded pits on an optical videodisk vary in depth. F The color-under process is necessary in optical videodisk recording. F
10-12 a. b. c. d.
The CED and VHD systems both use capacitance variations for signal. T The deeper the pit in a disk, the lesser the capacitance. The color-under system is used in the CED method bit not for optical disks. T Disk rotation is 450rpm in the CED system.
Chapter 11 Television Transmission 11-1 a. Maximum white 10 to 15, or 12.5 average b. Blanking 75 c. Tip of sync 100 11-2 a. b. c.
Vestigial sideband transmission of the AM picture signal. All the upper sideband is transmitted. T A part, or about 0 to 0.75 MHz of the lower sideband is transmitted. With 0.1-MHz modulation of a 61.25-Mhz carrier, the side frequencies are 61.15 and 61.35 MHz. T
11-3 a. b. c.
The picture and sound signals use separate. T The UHF television channels are 6 MHz wide. Channels 6 and 7 are most likely to have adjacent-channel interference. F.FM spectrum lies between channels 6 and 7.
11-4 a. b. c. d.
List the values for the following frequencies in Channel 4, which is 66 to 72 MHz. Picture carrier. 67.25 MHz. Upper side carrier for 3-MHz video modulation. 70.25 MHz. Color sub carrier. 70.83 MHz. Sound carrier. 71.75 MHz.
a. b. c.
Values for the FM sound signal in TV. Maximum frequency deviation. 25 kHz. Separation of center frequency from the picture carrier signal. 4.5 MHz. Percentage of modulation for +/- 20 kHz swing. 80%
a. b. c.
The tolerance for the picture carrier frequency is +/- 1000 Hz. The emission-type number for vestigial sideband transmission is A5C. The frequency offset for the cochannel stations. 10 kHz.
a. b. c. d.
Line-of-sight transmission uses sky waves from the ionosphere. F A half-wave dipole is shorter for higher frequencies. T Multipath signals cause ghosts in the picture. T The higher the antenna, the longer the radio horizon distance. T
a. b. c. d.
A 6 GHz is an uplink frequency. A 4 GHz is a downlink frequency. There are 1000 megahertz in a 1 GHz. Satellites differ in angular heading by 3-5 .
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Chapter 12 Television Receivers 12-1 1. Picture IF 2. Second sound IF carrier 3. Chroma after the video detector 4. Vertical Sync
45.75 Mhz. 4.5 Mhz 3.58 Mhz 60 Hz
12-2 a. b. c. d. e. f.
Is the sync used for the deflection oscillator of the amplifier? Oscillator The V oscillator frequency is too low, which control needs to be adjusted? V Hold The screen has too much black area across the bottom. Which control would you adjust? Height Is a sawtooth waveform of current needed in the V coils, H coils, or both? Both Is AFC used for the V or H deflection oscillator? H Oscillator Is high voltage for the picture tube anode produced by the V or H output circuit? H output circuit
12-3 a. b. c.
The AGC rectifier is a peak detector. T More AGC bias reduces the receiver gain. The AGC action keeps the picture contrast approximately the same for different station. T
12-4 a. b. c.
18 V – a typical dc supply voltage for small signal transistor amplifiers. 25 kV – the anode high voltage for a color picture tube. Horizontal Flyback – horizontal retrace time
12-5 a. b. c. d. e.
The local oscillator beat above the RF signal frequencies. RF Amplifier- stage in the tuner that is the most efficient in reducing oscillator radiation. Mixer- stage that produces the greatest receiver noise. 517 Mhz- the local oscillator frequency for the tuning in channel 14. IF Amplifier- stage in the receiver that the output signal of the VHF mixer feed.
12-6 a. b. c. d.
The 41.25 Mhz IF sound signal is 4.5 Mhz above the picture signal. The IF response at 45.75 Mhz is equal to 50 percent. Channel selectivity is determined IF. Video detector is the stage in the TV receiver that is driven by the IF section.
12-7 – wala lng 12-8 a. b. c.
AC video signal drive is varied by the contrast. The input signal for the video amplifier is supplied by the video detector. The video amplifier bandwidth in a monochrome receiver is generally 3.2 Mhz.
12-9 a. b.
The dc component of the video signal determine the brightness. The direct coupling method preserves the dc component.
12-10 a. b. c.
The frequency of the second sound IF signal when the receiver is tuned to UHF channel 14 is 4.5 MHz. The resonant frequency of the sound takeoff trap in the video circuits is 4.5 MHz. The maximum frequency deviation of the FM associate sound signal is 25 kHz.
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The mixer is the main source of receiver noise. A break in the IF section can cause the symptom of no picture on a clean raster without snow. T A break in the antenna circuit can cause the symptom of no picture but with snow. T An overload picture is usually out of sync. T
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A TV monitor does not have an RF tuner. T The standard level of composite video signal for connections between modular units is 1 Vp-p. A high-voltage supply for the picture tube is included in the TV monitor. T
Chapter 13 Raster circuits and Sync 13-1 a. b. c.
All the sync pulses have the same amplitude. T The synchronizing pulses produce the scanning raster. F The V sync pulse has the lowest frequency. T.
a. b. c.
The sync separator is a common-emitter amplifier. The separated sync includes all the sync pulses. T The separated sync is inverted from the pulses in the composite video signal. T.
a. b. c.
The input for the V integrator is taken from the sync separator. The output from the RC integrator is the voltage across C. A typical time constant for the vertical integrator is 50 s.
a d. e.
A single bright line across the center of the screen can be caused failure of the oscillator or amplifier or a defect in the coupling circuits or yoke. Too much black space at the bottom of the screen can be caused by weak vertical output. The dc bias on the vertical amplifier affects the height and linearity of the raster.
a. b.
The diagonal black bar represents H scanning. V Hold control makes the picture stop rolling.
a. b. c. d.
HAFC – Horizontal AFC. It is a PLL. HAFC is for horizontal sync. Horizontal Flyback is for high voltage. The output stage operates similar to class c amplifier.
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a. b. c. d.
The gen-lock system is used in television cameras and other studio equipment to provide the V and H drive signals. It provides excellent interlacing. The whole gen-lock circuit can be contained in one dedicated chip. T The master oscillator operates at 31.5 khz. No vertical hold is used. T
a. b.
For the TV power supply: The Tripler is for high voltage. The voltage regulator is used for the line rectifier.
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13-9 a.
No horizontal output results in a total loss of the raster since the Flyback high voltage depends on the horizontal output.
Chapter 14 Color Television Receiver Circuits 14-1 a. b. c.
The Y signal produces a monochrome picture. The drive controls adjusted for white. Color red generally does not have a drive control.
a. b. c.
When the blue gun is dead, the monochrome picture and raster will be yellow. T A monochrome picture can be produced without the 3.58-MHz chroma section. An open in the green output-adder stage results in a magenta picture. T
a. b. c.
The value of the beat frequency between the associated sound carrier and color subcarrier is 920 kHz. The beat frequency between the associated sound carrier and the picture carrier is 4.5 MHz. The relative gain for 42.17 MHz in the IF amplifier is 50%.
a. b. c. d. e. f.
The bandpass amplifier is tuned to 3.58 MHz with a typical bandwidth of +/- .05 MHz. T The color control varies the gain of the bandpass amplifier. T The burst amplifier is on during H Flyback time. A synchronous demodulator needs two input signals. T The AFPC circuit provides dc control voltage for the color oscillator. T The tint control adjusts for the phase angle f or the demodulated color video signals.
a. b. c.
Circuits that can cause the trouble of no color are Bandpass amplifier, color oscillator and color killer. A fixed phase error in the color oscillator causes wrong hues. The R-Y demodulator fails, colors red and cyan will be missing from the picture.
a. b. c. d.
The ACC circuit varies the gain of the first BPA. The manual color control varies the amplitude of the 3.58 MHz chroma signal. The output from the BPA feed the demodulators. The burst amplitude used to determine the ACC bias.
a. b. c.
The color killer bias is on the PBA. T Burst is used to produce the dc bias from the color-killer diode detector. T Color snow, or confetti is predominantly magenta. T
a. b. c.
The angle between R-Y and B-Y is 90 . The bandwidth of the I signal is 1.3MHz. DC coupling used for the demodulator output.
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14-10 a. b. c. d.
The crystal ringer is shock-excited by color burst. T In an AFPC phase detector, the burst and oscillator cw signals are 90 out of phase. The burst separator is off during horizontal trace line. T No color sync means that colors drift through the picture. T
Chapter 15 Cable Television 15-1 a. b.
The superband channel number just above VHF broadcast channel 13 is 23. VHF broadcast channel does a TV receiver with a cable converter stay tuned at 2,3 or 4.
15-2 a. b. c.
The outer conductor of coaxial cable serves as a shield. Generally RG-59U cable is used for the drop line. T Thinner cable has greater losses. T
a. b. c. d.
The value of R that was used to terminate RG-59U coaxial cable for impedance matching is 75 ohms. A line with more C per unit length has a lower Zo. Open ends of transmission line correspond to a parallel resonant circuit. The value of the VSWR when a cable is terminated in its Zo is 1.0.
a. b. c.
Cable losses increases at higher frequencies. T 2 Coaxial cables have I R losses. A 6-dB loss reduces the signal level by one-half.
a. b. c. d.
The head end of a cable system is the starting point of cable signals. T A trunk cable is the main line for cable signals. T The insertion loss is lower than the tap loss for line taps. A balun is used to match the 75- coaxial cable to the 300- receiver input.
a. b. c.
The reference level for the dBmV unit is 1mV. The signal level of 2 mV in dBmV units is 6dBmV. The signal level of 0.5 mV in dBmV units is –6 dBmV.
a. b. c.
Sync and blanking bars from another channel can be caused by overload distortion. T Losses increase with higher temperature. A slope-control circuit increases the amplifier gain for higher-frequency channels. T
a. b. c.
In two-way cable systems, the same cable for downstream and upstream signals. The upstream signal is in the band of 5 to 30 MHz. The poling signal is in the band of 107 to 119 MHz.
a. b. c. d.
The cable converter uses two local oscillators. T The video IF carrier in a cable converter is generally 612.75 MHz. The local oscillator for the up converter operates in the UHF range. T Each cable channel is selected by setting the frequency of the VCO for the up converter. T
15-3
15-4
15-5
15-6
15-7
15-8
15-9
15-10 a. b. c.
Wave traps to attenuate premium channels are usually located in the feed line to each subscriber. A scrambled channel usually has a picture that is out of sync, as evidenced by rolling and diagonal bars. A scrambles channel needs decoding pulses to restore the sync. T
15-11 a. b. c.
Supertrunks have the cable channels that are heterodyned down to lower frequencies. The frequency of 13 GHz is in the microwave band. T FM can be used for microwave links for television. T
15-12 a. b. c. d. e.
Fiber-optics cable has very low losses. T A light-modulated signal is limited to narrow bandwidth in the modulation. F Refraction means the bending of light waves. T Fiber-optic cable makes use of internal reflections of light. T Typical index of refractions: glass- 1.8, diamond-2.4, water-1.3
Chapter 16 Television and Video Servicing 16-1 a. b.
An isolation transformer has separate primary and secondary windings. T The wider blade in a polarized ac line plug connects to the chassis in receivers with a line-operated halfwave rectifier. T
a. b. c.
DMM has higher resistance as a dc voltmeter. Meter loading decreases the voltage reading. The external multiplier for a high-voltage probe is 900M .
a.
An oscilloscope with a 50 MHz bandwidth must be used for TV servicing. F
16-3
16-4
b. c. d. e.
The TV switch on an oscilloscope can be set for two cycles of video signal, at either the V or the H scanning rate. T A dual-beam oscilloscope has a CRT with two electron guns. A delayed-sweep oscilloscope uses two internal time bases. T A tuner subber produces the IF output signal. T
a. b. c.
The NTSC color-bar generator produces standard chroma and luminance values. T The color bars in a gated rainbow pattern differ in hue phase by 30 . Color bars have the standard amplitude of 75 IRE units.
a. b. c.
The range of the tint control when it can move a color one bar to the left and right is +/-30. Which color-difference signal has the same phase as the burst? (B-Y) Which color bar has the output from a B-Y demodulator? Sixth
a. b.
No horizontal output can kill the sound. T A receiver with current in the ADG coils has AC power input. T.
a. b.
Two pairs of horizontal bars are produced by 120-Hz ripple in the video signal. T. Hum in the sync can cause bend in the picture. T.
a. b. c. d. e.
If the anode potential drops a few kilowatts, the raster will be bigger. A gassy picture tube can make the anode voltage too low. Blooming in the picture tube indicates a poor HV regulation. The grounded clip lead should be connected first in order to discharge the high voltage. The picture tube shows a thin vertical line before the screen goes black. The trouble is in the Horizontal Oscillator.
16-5
16-6
16-7
16-8
16-9
16-10 All answers are TRUE. a. Transformer T1 is the horizontal output transformer. b. Conduction in the SCR kills the high voltage. 16-11 a. b. c. 16-12 a. b. c. d.
An inexpensive way to obtain a good alignment tape is a copy the manufacturer’s original. F A large error in the scanner rotational speed makes the picture look as if it were out of horizontal sync. T. Excessive moisture can trigger the automatic stop in a VCR. T.
Ina single-tube color camera, the problem of no color can be paused by poor electrical focus. T. Balancing red, green and blue for color camera is done by pointing the camera at a stair-step reflectance chart. Insufficient beam current in a vidicon causes a low-contrast picture. T. The standard output voltage from a color camera is 1V p-p.
END CHAPTER QUESTIONS: Chapter 1 Applications of Television
Matching Type 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
Vidicon Baseband signal TV channel bandwidth Channel 2 frequencies Amplitude modulation Frequency modulation Picture frames per second Horizontal lines per frame Cable television Special-effects generator Channel 3 or 4 Infrared TV Facsimile Coaxial cable impedance Chroma signal Byte Intercarrier frequency Anode high voltage
-
Camera tube Video signal 6 MHz 54 to 60 MHz RF picture carrier signal RF sound carrier signal 30 525 Head end SEG VCR RF output Closed-circuit TV Slow-scan TV 75 ohms 3.58 MHz 8 bits 4.5 MHz Brightness
Chapter 3 Television Cameras Fill in the blanks. 1.
Plumbicon is a camera tube that uses a lead oxide (PbO) for the photoconductive target plate.
2.
Camera signal output without sync is called non-composite video.
3.
A low-contrast picture in which white seems flat and lacking in detail suggests a low beam current.
4.
A Plumbicon is a camera tube that has a minimum lag.
5.
The part of the invisible spectrum where camera pickup tubes have the greatest output is the yellowgreen.
6.
Precise scanning size and linearity are most important in a single-tube color pickup.
7.
Beam alignment magnets for the camera tube are adjusted while rocking which control the electrical focus.
8.
Special effects and production switching are done by the SEG.
9.
The gamma of the picture tube is 2.2.
10. If the camera cannot be placed far away enough to include everything in the scene, change the lens to one with a shorter focal length. 11. A typical value of vidicon dark current is 0.2 A. 12. A lens has an 8-cm focal length and 4-cm diameter. Its f rating is 2.
Chapter 6 Scanning and Synchronizing Fill in the blanks. 1.
In the sawtooth waveform for linear scanning the complete cycle includes trace and retrace.
2.
Given a 635-s vertical retrace time, the number of complete horizontal lines scanned during vertical flyback is 10.
3.
One-half line spacing between the start positions for scanning even and odd fields produces exact interlacing.
4.
The number of lines scanned per frame in the raster on the picture tube screen is 525.
5.
In the frame for which interlaced scanning is used, alternate lines are skipped during vertical scanning because the vertical scanning frequency is doubled from 30 to 60 Hz.
6.
If the horizontal flyback is 10%, this time equals 6.4 s.
7.
“The keystone effect produces a square raster”- it is a false statement.
8.
The width of a vertical sync pulse with its serrations includes the time of six half-lines, or three lines.
9.
Sawtooth generator circuits produce the scanning raster, but the sync pulses are needed for timing.
10. “31,500 Hz for the vertical scanning frequency” is a wrong assertion.
Chapter 8 Color Television: Circuits and Signals Fill in the blanks. 1.
Brightness variations of the picture information are in the Y signal.
2.
The hue 180 out of phase with red is a cyan.
3.
Greater p-p amplitude of the 3.58-MHz chrominance signal indicates more saturation.
4.
The interfering beat frequency of 920 kHz is between the 3.58-MHz color subcarrier and the 4.5 MHZ intercarrier sounds.
5.
The hue of color sync phase is yellow green.
6.
I signal has color information for 1.3-MHz bandwidth.
7.
“A fully saturated color is mostly white.” – it is a false statement.
8.
The color with the most luminance is yellow.
9.
The hue of a color 90 leading sync burst phase is cyan.
10. The average voltage value of the 3.58-MHz modulated chrominance signal is the brightness of the color. 11. The second IF value for color in receivers, for any station, is 3.58 MHz. 12. If the 3.58-MHz C amplifier in the receiver does not operate, the result will be no color.
Chapter 10 From the multiple choice questions: 1.
How many octaves is the frequency range of 1 to 8? 3
2.
Which system can be used for both recording and playback? VHS
3.
How many TV fields are recorded on one slant track of tape? 1
4.
The video heads rotate at high velocity to increase the writing speed.
5.
A typical frequency for the FM luminance signal in VCR recording is 3.5 Mhz.
6.
Which of the following applies to the color-under technique? Chroma frequencies are reduced.
7.
What oscillator frequency is needed to heterodyne 629 khz up to 3.58 Mhz? 4.21 Mhz
8.
A comb filter is used to cancel chroma crosstalk.
9.
Switching for each field is required for the video heads.
10.
Servocontrol of speed and phase is used for the video scanner head.
11.
The part that rotates to meter o the tape at constant speed is capstan.
12.
To make the tape speed the same in playback as in recording, the tapespeed is regulated by the controltrack pulses.
13.
Tilting the video head gaps is necessary with the zero guard bands.
14.
Which system uses a laser light beam for playback? VLP
15.
In the CED system, the disk capacitance varies with the pit depth.
Chapter 11 1.
The modulated picture carrier wave includes the composite video signal as the symmetric carrier level without the lower envelope.
2.
Which of the following statements is true? Negative transmission means that the carrier amplitude decreases for black.
3.
With a 2 Mhz video signal modulating the picture carrier signal for channel 4 (66 to 72 Mhz), which of the following frequencies are transmitted? 67.25 Mhz carrier frequency and 69.25 upper side frequency.
4.
With a 0.5 Mhz video signal modulating the picture carrier, both upper and lower side frequencies are transmitted.
5.
In all standard television broadcast channels, the difference between the picture and sound carrier frequencies is 4.5 Mhz.
6.
The difference between the sound carrier frequencies in two adjacent channels is 6 Mhz.
7.
Line-of-sight transmission is a characteristic of propagation for the VHF band and higher frequencies.
8.
In channel 14 (470 to 476 Mhz), the 3.58 color signal is transmitted at 474.83 Mhz.
9.
The difference between the sound carrier and color subcarrier frequencies is 0.92 Mhz.
10.
The maximum deviation of the FM sound signal, in kilohertz is 25 kHz.
Chapter 12 1.
Contrast of picture
Video amplifier
2.
Audio signal output
FM detector
3.
Gain control of RF and IF
AGC
4.
IF conversion
Mixer
5.
Synchronization of picture
Sync separator
6.
Brightness of raster
High-voltage supply
7.
DC electrode voltages
Low-voltage supply
8.
Snowy picture
RF amplifier
9.
Adjacent-channel selectivity
IF wave traps
10.
Baseband video signal
Video detector
Chapter 14 1.
Which of the following applies for a monochrome picture? Chroma amplifier off.
2.
Which of the following is not tuned to 3.58 Mhz? Video preamplifier
3.
The contrast control is in the Y video amplifier.
4.
The color level control is in the BPA.
5.
The color oscillator does not operate. The trouble is no color.
6.
The balance for Y video signals to the three guns in the picture tube is set by the drive controls.
7.
Which needs a 0.8s time delay? Y video.
8.
The output of the burst separator feeds the AFPC for color oscillator.
9.
The output of the color oscillator feeds the color demodulators.
10.
Drifting color bars in the picture indicate trouble in the AFPC for color oscillator.
11.
The beat frequency between the 3.58 color subcarrier and the 4.5 Mhz sound signal is 0.92 MHz.
12.
Which control varies the phase angle of the color video signal? Tint
13.
Which of the following stages has the bias from the AGC and color killer circuits? Chroma BPA.
14.
Which of the following stages must be on during horizontal Flyback time? Burst separator.
15.
A crystal-ringer circuit is used for the AFPC on color oscillator.
Chapter 15 1.
Which of the ff is a midband cable TV channel is A or 14.
2.
Coaxial cable for distribution systems has an impedance of 150 ohms.
3.
The cable converter output for the TV receiver is usually on channel 3.
4.
A tap for the subscriber drop line has a high tap loss.
5.
The most popular plug for the RG-59U coaxial cable is the F connector.
6.
Which of the ff is true? Weak signal causes snow in the picture.
7.
The upstream signal in two-way cable systems has the frequency of 5 to 30 MHz.
8.
A typical value for the IF signal, in megahertz, for up-down cable converter is 612.75.
9.
Frequency synthesis is used for the VCO in the up-converter.
10.
For in-band descramblers, the decoding pulses are sent on the sound carrier.
11.
A trunk cable run has a loss of –20 dBmV. To make up for this loss, the voltage gain of the next amplifier should be at least 10.
