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67776 2010 年 07 月 28 日 23:41 Reading (loading. ..) Comments (0) Category: Personal Diary
Transfer from: Beijing TV repair blog, although not complete,
la gear walking shoes, but still very interesting.
learned TV repair personnel, whether they are professional or amateur, most people would feel more abstract theoretical beginner, esoteric. The author is no exception, the original new to when a headache on the theory that some simply can not understand. In the later practice and teaching of the repair digesting slowly, and finally not only mastered the theoretical knowledge, but also explored in the teaching work so easy for beginners to understand some of the ingenious theory of knowledge of experience, beginners are introduced to the maintenance of the Friends TV reference.
one, electricity and water associated
electricity is invisible, intangible (low), and in order to master its features, thanks to information on the presentations and their own imagination, really difficult to understand.
water is very familiar to both see and touch the people every day without water, the physical properties it is understood.
metaphor of water, electricity if we, the current, voltage, resistance, alternating current, direct current, leakage, twisted wave circuits, capacitors, and other terms it is easy to understand. The electricity as water, the current equivalent of water, voltage is equivalent to water pressure, water resistance equivalent to the barrier, leakage is equivalent to leaking, be able to wave the equivalent of water waves,
la gear sneakers, water equivalent circuit, the capacitor is equivalent to water storage container.
in the amplifier circuit, the first to get the appropriate DC voltage, it can work. For example, the NPN-type transistor amplifier tubes, then the DC current flows from the transistor's base-emitter, and collector-emitter current is flowing, the DC current direction is fixed, the equivalent of the river's flow; However, to be transistor amplified AC signal its current direction is regularly changed. This point is difficult to understand for beginners, since the DC current (voltage) is much larger than AC signal current (voltage), DC and how it will reverse them? Besides also transistor conduction current (voltage) direction of contradictions. Clever is not difficult to understand, to where the DC current flow as a large river; and the AC signal current as a large river motor boats, although the direction of flow the same, but motor boats sail both downstream can also be sailing against the current . Without water, the boat can not row (transistor no static current, no amplification.)
Second, the TV signal distribution associated with the transport
radio and television signals in the transmit side, video and audio signals must modulated high-frequency signal through the antenna out (video and audio signals can not directly launch). On the receiving end (TV), should receive high-frequency television signal into a fixed intermediate frequency signal (38MHZ), after amplification and other processing, recovery (demodulation) into the transmitter of video and audio signals, and then sent to their relevant the circuit to go. We put audio and video signals as the two neighbors,
la gear police, and together they travel to distant places (not suitable for walking),
la gears, lost flight (aircraft) procedures is modulated high-frequency signals, the aircraft is launched off the aircraft after a flight landing is received, they were further from the destination (airport) is turned into a taxi with the IF signal, the distance travel by public transport is off the end with the demodulation of the last their walk to their destination.
Third, the amplifier associated with the vehicle
amplifier is able to amplify weak signals of electronic devices, easy for beginners to understand,
la gear sale, both like a magnifying glass, does not conform to energy conservation. Auto throttle we all know, it is to control the vehicle speed in the same gear, the throttle was greater the faster the speed, whereas the more slowly. Car throttle is controlled by the driver's feet to the foot speed determines the speed of force, then we can consider that car to the foot to force the driver to enlarge the car is the amplifier, the foot is weak signal with the power, speed is enlarged signal. Nature is to achieve energy amplification control,
la gear, that is large with a small power to control energy, and energy conservation are not contradictory.
IV
inductance inductance associated with the love is always impede the current flowing through the coil changes, that is, not only hinder the inductor current flowing through the coil changes, but also impede the current flow through the smaller coil, where inductance likened girl, likened by the current situation; guy chasing girls, girls, while agreeing, but cautious, they have to go through the process of first love, love, progress can not be too fast, the girl (inductance) Progress of Love (current changes) play impediment. After a period of time with the girl on the boy very happy and feel devotion, when the guy if the cool girl, girl (inductance) will hold small group of hot pursuit, obstruction love back (current decreases). If the guy suddenly interrupted love, and along with (guy) disappeared, the girl suffers a mental shock, resulting in unimaginable consequences (sudden cut off the current flowing through the coil, the coil will produce a high force, damage to the circuit components).
V. feedback associated with the market economy
feedback is removed from the part of the amplifier output voltage or current signals sent back through some of the circuit input. Output signal is fed to the input of the amplifier increased magnification, called positive feedback, reduces magnification the amplifier, called a negative feedback. Here compared to the factory amplifier output compared to product distributors, dealers from all over the sales information obtained through certain channels to the factory, the same plant are very popular with customers welcome reflected, is hot, required to ensure supply supply, the factory working overtime to increase production immediately, to prevent out of stock (positive feedback). If you are reflecting sluggish sales, or even to sell their products, the factory is about to stop or reduce production to prevent excessive backlog of products (negative feedback).
VI sync signal associated with the Beijing
sync signal into horizontal sync signal and vertical sync signals, they were so horizontal and vertical scanning and sending the same frequency and phase. Requires the same frequency can be understood, but there are some difficulties understanding the phase. We are very familiar with the time clocks used in the country should be subject to Beijing, CCTV and the Central Broadcasting Station at intervals of 1 hour (full time) have reported that a Beijing time (synchronous signal), one of the reasons is to us watch on their own time (horizontal and vertical scanning signal) with which (synchronous signal) compared to most if the time error correction. If you buy a new watch or a very accurate clock, even though the Hong Kong Observatory and the Nanjing Purple bell Jingshan as precise, we can only say that they are the same frequency (same frequency), in Beijing before use must be corrected (to maintain the same phase) Otherwise, only the same frequency and different phase, did not use significance. For example, Beijing is 9 o'clock, and your new watch just before 5 o'clock, if not the school