電子產(chǎn)品調(diào)試與測試總復(fù)習(xí)電視技術(shù)小知識（General review of electronic products debugging and testing, TV technology, little knowledge）

1、電子產(chǎn)品調(diào)試與測試總復(fù)習(xí)電視技術(shù)小知識（General review of electronic products debugging and testing, TV technology, little knowledge）The tube is a kind of special electric vacuum device, the electron gun is mainly composed of filament cathode, grid, accelerator, focusing electrode and high voltage anode etc.The interla

2、ced broadcast television system used in China, the frequency is 15625Hz, frequency is 50Hz, the frame rate of 25Hz.The three elements of color refers to the brightness, hue, color saturationThe three primary colors used in television system are red (R), green (G) and blue (B)Which color TV signal in

3、cluding luminance signal, chrominance signal, color synchronization signal, the composite sync signal, composite blanking signal.In the television system used in China, modulation of image and audio are am and FMThe basic components include tuner input circuit, a high frequency amplifier, frequency

4、conversion circuit etc.The main part in channel circuit, including pre SAW filter, amplifier, video frequency detector, AGC, ANC etc.Composition of the luminance channel including the color subcarrier in the final brightness filter, delay circuit, DC clamp circuit, contour compensation circuit, vide

5、o amplifier circuit etc.Audio channel consists of audio format conversion circuit, audio circuit, audio frequency discriminator circuit, amplifier circuit, power amplifier circuit lowComposition of scanning system includes a synchronous separation circuit, scanning circuit, field scanning circuitCom

6、position of the line scanning circuit includes AFC circuit, oscillation circuit, driving circuit, output circuit etc.? field scanning circuit includes field oscillation circuit, sawtooth wave forming circuit, driving circuit, field field output circuitThree color system is popular in the world today

7、 are PAL, NTSC system and SECAM systemThe main component of the NTSC encoder including encoding matrix, low-pass filter, subcarrier oscillator, delay circuit, balanced modulator, adderNTSC decoder is mainly composed of a band-pass filter, subcarrier recovery circuit, synchronous detector, delay circ

8、uit, matrix circuit, subcarrier trapPAL encoder adds inverter, PAL switch circuit compared with NTSC encoder.In the PAL decoder, composed of a comb filter including the adder, subtracter, a delay line circuit.PAL decoder consists of brightness, chroma channel, subcarrier recovery circuit, decoding c

9、ircuitIn the PAL decoder, which includes the chrominance channel chroma bandpass amplifier, ACC circuit, ACK circuit, comb filter, synchronous detectorThe main circuit includes color subcarrier recovery synchronous gating circuit, voltage controlled oscillator, phase detector, low pass filter, PAL s

10、witch, 90o phase shifterThe RF television signal, audio frequency than the image carrier frequency high 6.5MHz.Image signal with negative polarity modulation with positive modulation has higher power utilization.Video signal in the equalizing pulse is applied to overcome the parallel phenomenon.A co

11、lor television system does not send and receive green difference signal.My TV signal adopting negative polarity modulation.Second TV Sound IF signal is generated by the image and sound if the first intermediate frequency mixing.Contour compensation circuit (contouring circuit) is essentially a lumin

12、ance signal high frequency compensation circuit.Surface acoustic wave filter is formed if the amplitude frequency characteristic curve.Method of varactor tuner by changing the varactor bias tuning.The TV video output is large signal voltage amplifier.Adjust the video amplifier circuit can change the

13、 gain of image contrast.In the current field deflection coil current is sawtooth shaped.Field scanning circuit of the sawtooth wave forming circuit usually consists of RC components.The control object of the AGC circuit is high frequency amplifier and intermediate frequency amplifier.The three color

14、 signal processing process combination form color TV signal is called encoding.PAL color balance amplitude modulation wave without carrier frequency component 4.43MHz.A color television system does not send and receive green difference signal.In the color TV in red, green and blue three colors calle

15、d, any color can be produced by the other two kinds of color mixing.The United States, Japan and other countries to use the NTSC for TV, video signal bandwidth is only 4.2MHz.Each boot time, color TV will be an automatic degaussing.The high frequency tuner in the vibration vibration stop, there will

16、 be no image, no sound phenomenon.Synchronous separation circuit failure, will cause the horizontal and vertical synchronization phenomenon.If the gray box TV test card in both with a certain color, that color purity is not adjusted.When the fault occurs when the scanning circuit, may also cause the

17、 TV "three noes" phenomenon.Fault automatic degaussing circuit, may lead to the emergence of local color TV screen is not a normal phenomenon.When the TV (scanning current nonlinear), pictures will appear in the vertical direction of the imbalance phenomenon.In the interlaced scanning TV s

18、ystem used in China, field scan signal frequency is (50) HzIn PAL color TV, line scan signal frequency (15625Hz.PALD color TV, if the frequency of image carrier (38) MHz.The TV system in our country, the image signal using VSB transmission, the main reason is (to save bandwidth).China's televisi

19、on system, second audio frequency is (6.5) MHz.The size of the electron beam tube (potential difference between the gate and cathode) control.Electron beam tube is generated (electron gun).The aural signal used in China (SSB) sent.The frequency range of TV signal for (0 6) MHz.The role of tube filam

20、ent (heating cathode).In a television signal field blanking signal frequency (50 Hz).The TV can be interlaced (to solve the flicker problem).Our common TV is used (interlaced).The provisions of TV standards in China: modulation image signal (for negative modulation).The provisions of TV standards in

21、 China: the TV picture is transmitted per second (25 frames).Compared to color TV signal and compositevideo signal mainly increased (chroma and color synchronization signal).Explain the principle of three primary colors, brightness color light obtained by mixing equal to three colors (three colors a

22、nd brightness).China's TV image signal using (vestigial sideband) transmissionThe provisions of TV standards in China: video signal band width (6MHz?).China's TV sweep parameters in line for (15.625kHz).Negative video signal level is higher,The image (the black).The provisions of TV standard

23、s in China: each channel band width (8MHz).Scanning mode of China's TV is currently used (interlaced).Scanning China TV standard (is interlaced, 312.5 line / field).In the TV fault causes interference image may be (6.5MHz snubbercircuit offset)Color TV color grating blue (white balance) belongs

24、to fault.Which color TV signal comprises a luminance signal and chrominance signal, color synchronization signal, the composite sync signal composite blanking signalThe three elements of color refers to the brightness, hue, color saturationThe three primary colors used in television system are red g

25、reen blueColor TV is compatible with the black and white television, based on the principle of large area coloring principle, spectrum interleave techniqueDo not belong to the periodic signal is the image signal, the color signal and sound signalColor TV, put in the control range is about AGC (40) d

26、B.In the switching power supply circuit, power supply switch (switch) in the state.Automatic degaussing circuit of color TV, the resistance is (thermistor).The synchronous separation circuit is separated from the color TV signal (composite sync signal) signal.From the composite sync signal separatio

27、n circuit of the synchronous signal is played (integral) circuit.China's television standard, sound modulation signal with a bandwidth of kHz (130).The current line deflection coil in the waveform is (Ju Chibo).Oscillation signal waveform is generated for oscillator (rectangular pulse wave).High

28、 bandwidth (greater than 8) MHz.AGC refers to the circuit (automatic gain control) circuit.Absorption circuit in TV is (band stop) filter.In order to synchronize any free oscillation frequency of the oscillator should be field (less than 50Hz)The current line deflection coil in the waveform is (Ju C

29、hibo).The PAL system of TV image signal demodulation is used (synchronous detector).The output tube (switch) working in the state.Synchronous separation integral circuit used in circuit isolated from composite synchronization signal (field sync pulse).In a television receiver amplitude frequency cha

30、racteristic curve in the image on the carrier frequency (0.75MHz) range curve is a slope.In television, separated from the video signal in a circuit is a composite synchronization signal (amplitude separation circuit).The ABL is a circuit that limits the image (brightness).Surface acoustic wave filt

31、er is (discharge characteristic curve in the formation of a one-time).The television receiver image signal by the following definition in the signal (luminance) decision.The control object is AFT circuit (LO in LNB) circuit.In the TV tuner has the general requirements, (20) the control range of dB A

32、GC.The tube includes the internal electrode (cathode, anode, gate, focus).Composition of the line scanning circuit (including line oscillator, AFC circuit, drive circuit, line output stage).The AFT signal can be used (the vibration frequency and the stability of the automatic search as a tuner to ca

33、pture the signal process).Including the composition of the TV tuner (high frequency amplifier local oscillator mixer input circuit).Color TV circuit, signal output by the video detector (color TV signal second sound signal).In a television receiver signal processing circuit, which belongs to the com

34、mon circuit (audio frequency amplifier amplifier mixer circuit).Put the TV in the amplitude frequency characteristic curve, frequency absorption is required (30MHz 31.5MHz39.5MHz).The luminance channel of color TV (mainly by the subcarrier trap delay circuit for video amplifier).After the path of TV

35、 sound signal (audio amplifiers have video detector frequency discriminator circuit in LNB).The output signal tuner, frequency signal useful (31.5MHz 33.57MHz 38MHz).The main function is to realize the electron gun electron beam (emission accelerated focus modulation).Including the composition of th

36、e television channel put (video detector ANC intermediate frequency amplifier circuit).The electron gun CRT (cathode filament by the gate).Public TV channel (including on channel high-frequency tuner).In a television, control object AGC circuit (high frequency amplifier is placed in the front stage)

37、Including the composition of TV switching power supply (rectifier circuit filter circuit sampling circuit protection circuit).Including automatic degaussing circuit (degaussing coil thermistor).Switch type power supply compared with the stabilized power supply, with (without power transformer with h

38、igh efficiency, low power consumption and high reliability stability adapt to a wide range of voltage) characteristics.In a color television system, the signal is transmitted (RY, B-Y, Y).ACC (automatic circuit refers to the color saturation control circuit).Color TV signal decoder is output (three

39、primary signal).Color TV, color signal is a (both amplitude and phase modulation) modulation signal.PAL, pal signal (FV signal).The difference between PALD and PALI standard is (second sound if).In a color television system, as chroma signal transmission is (two color difference signals).PAL color d

40、ifference signal band width (1.3MHz).Three color R=G=B color TV signal, grating color (white).Color subcarrier frequency PALD color TV is (4.43) MHz.NTSC refers to two color difference signals (respectively on the same frequency and phase difference of 90 DEG) of the subcarrier balance amplitude mod

41、ulation.In the process of forming color television signals, compressed color signal frequency band (low pass filter) is through to complete.Color TV receiver, the comb filter is (U, V signal separation).In a color television system, the three primary signal into R -Y, Y, B circuit, Y (encoding) is c

42、alled.Color TV receiver of color signal is separated by (band pass filter).From the color TV signal in the process of taking out three color signals called (decoding).Color synchronizing signal is (subcarrier form).Chrominance signal is an amplitude modulation and phase modulation signal,The amplitu

43、de and phase respectively represent the color (hue and saturation).PAL color TV signal with two color difference signals on quadrature amplitude modulation subcarrier, the purpose is to solve the problem (two color difference signal phase).Two color difference signal is transmitted at the same time,

44、 color TV (R-Y and B-Y).China's current TV system (PALD system).The PAL system of modulation of the color difference signal is (quadrature amplitude modulation).Comb filter in (chroma) circuit.Color TV ultrasonic delay time is 63.943 microseconds.Color TV signal, color synchronizing signal is (t

45、o ensure correct demodulation color).Color synchronizing signal position (line blanking shoulder).Separation method for color signal and color synchronizing signal is (time separation method).PAL decoder, 4.43MHz bandpass filter is removed from the color TV signal (chroma and color synchronization s

46、ignal).The color of the color saturation refers to the color (depth).In a color television system, signal encoder output is (color TV signal).When the brightness signal set is increased, the corresponding color saturation will (decrease).Compared with the TV signal of TV signal with black and white

47、TV color TV, increased (chroma and color synchronization signal).Color TV signal encoder, the three color signal encoding for (Y RY B-Y).In color TV, CRT signal is applied to the cathode (green red blue color signal signal signal).PAL color TV, including a decoder component (recovery circuit decodin

48、g matrix chrominance subcarrier channel brightness).The chrominance signal passing path (put channel comb filter in LNB).In color TV, color synchronization signal after the circuit (high frequency amplifier videodetector ribbon filter).In the PAL decoder, including circuit restoring reference subcar

49、rier (subcarrier generator phase detector PAL switching frequency and half line amplifier).When the grating background color on a TV screen is green, indicating the presence of (white balance) fault.Color TV sets off the filament tube will appear (Wu Guangzha).When the electron gun axis and the tube

50、 axis do not coincide, there will be (the grating center is not in the center of the screen) phenomenon.The blue color TV and the blue beam electron gun off due to a fault, the screen will show (yellow color).Watch TV escape phenomenon after a period of time, the cause of the failure is possible (tu

51、ning voltage instability).When the TV sound is normal, and the image is blurred, failure may be due to (kinescope and accessory circuit).The TV in the field scanning circuit stops working, there will be a (horizontal line) fault phenomenon.When the tuning voltage generating circuit failure, may appe

52、ar (not pictured silent) fault phenomenon.When a fault occurs the decoder circuit, there will be (no color) fault phenomenon.Color TV tube gate circuit will appear (no image).When the bad convergence time of CRT (color edge) will appear.When the fault phenomenon of TV sound normal without the grating,The main check (line scanning circuit) circuit.If the TV tuner failure is (not only affect the image and sound effects).Color TV "X ray protection" in the circuit (high voltage high) protection.Treadmill phenomenon of television a