Start Grob TV End Chapter Exercise 12
Answers are Underlined
Chapter 12
Television Receivers
12-1
- 1. Picture IF 45.75 Mhz.
- 2. Second sound IF carrier 4.5 Mhz
- 3. Chroma after the video detector 3.58 Mhz
- 4. Vertical Sync 60 Hz
12-2
- a. Is the sync used for the deflection oscillator of the amplifier? Oscillator
- b. The V oscillator frequency is too low, which control needs to be adjusted? V Hold
- c. The screen has too much black area across the bottom. Which control would you adjust? Height
- d. Is a sawtooth waveform of current needed in the V coils, H coils, or both? Both
- e. Is AFC used for the V or H deflection oscillator? H Oscillator
- f. Is high voltage for the picture tube anode produced by the V or H output circuit? H output circuit
12-3
- a. The AGC rectifier is a peak detector. T
- b. More AGC bias reduces the receiver gain.
- c. The AGC action keeps the picture contrast approximately the same for different station. T
12-4
- a. 18 V – a typical dc supply voltage for small signal transistor amplifiers.
- b. 25 kV – the anode high voltage for a color picture tube.
- c. Horizontal Flyback – horizontal retrace time
12-5
- a. The local oscillator beat above the RF signal frequencies.
- b. RF Amplifier - stage in the tuner that is the most efficient in reducing oscillator radiation.
- c. Mixer - stage that produces the greatest receiver noise.
- d. 517 Mhz - the local oscillator frequency for the tuning in channel 14.
- e. IF Amplifier - stage in the receiver that the output signal of the VHF mixer feed.
12-6
- a. The 41.25 Mhz IF sound signal is 4.5 Mhz above the picture signal.
- b. The IF response at 45.75 Mhz is equal to 50 percent.
- c. Channel selectivity is determined IF.
- d. Video detector is the stage in the TV receiver that is driven by the IF section.
12-8
- a. AC video signal drive is varied by the contrast.
- b. The input signal for the video amplifier is supplied by the video detector.
- c. The video amplifier bandwidth in a monochrome receiver is generally 3.2 Mhz.
12-9
- a. The dc component of the video signal determine the brightness.
- b. The direct coupling method preserves the dc component.
12-10
- a. The frequency of the second sound IF signal when the receiver is tuned to UHF channel 14 is 4.5 MHz.
- b. The resonant frequency of the sound takeoff trap in the video circuits is 4.5 MHz.
- c. The maximum frequency deviation of the FM associate sound signal is 25 kHz.
12-11
- a. The mixer is the main source of receiver noise.
- b. A break in the IF section can cause the symptom of no picture on a clean raster without snow. T
- c. A break in the antenna circuit can cause the symptom of no picture but with snow. T
- d. An overload picture is usually out of sync. T
12-12
- a. A TV monitor does not have an RF tuner. T
- b. The standard level of composite video signal for connections between modular units is 1 Vp-p.
- c. A high-voltage supply for the picture tube is included in the TV monitor. T
Matching Type:
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1. Contrast of picture 2. Audio signal output 3. Gain control of RF and IF 4. IF conversion 5. Synchronization of picture 6. Brightness of raster 7. DC electrode voltages 8. Snowy picture 9. Adjacent-channel selectivity 10. Baseband video signal |
Video amplifier FM detector AGC Mixer Sync separator High-voltage supply Low-voltage supply RF amplifier IF wave traps Video detector |
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