The part such as the bar net inside picture tube of colour television machine, shade cover uses metallic stuff make it. Geomagnetic field, all round the magnetic field that when stray magnetic field and television work normally, forms inside machine, can make this this metal component is magnetized, what make electron beam blasts off thereby is red, blue, green the athletic contrail of 3 electron beam produces not due deviate, cannot hit the pigment of corresponding red, blue, green fluorescent material on fluorescent screen well and truly on base point, can produce unusual color so (or irregular splash) . To eliminate the magnetization appearance that the likelihood on picture tube appears, automatic degauss circuit was installed in color television.

One, the principle of common degauss circuit
The automatic degauss circuit in machine of common colour television is general person comprise by two, namely degauss coil and degauss resistor, graph 1 for 3 kinds common degauss circuit principle pursues. The degauss resistor of the action in machine of common colour television is a kind nonlinear resistor, call PTC resistor commonly (PTC is the) of English prefix abbreviate of temperature coefficient. The R-t character of this kind of resistor is very special (see the graph shows) 2 times, it is it is by BaTiO3 base the material of pottery and porcelain that expects the semiconductor that pass impure modified and forms is changed is made, and BaTiO3 has a Courier to nod (see a picture 2 medium Te are nodded, when make, through adjusting a recipe, the Courier that can change material is nodded, in order to get used to all sorts of different utility) , around Courier dot, make block cost rises quickly as a result of the reason that changes, in limits of this temperature above, material assumes open circuit position. The Courier dot of the degauss resistor that uses in color television is tens of spending commonly, below normal temperature, its block value reachs tens of Europe for ten Europe commonly. Accordingly, in the instant that switch on the mobile phone, through degauss loop (see the graph is shown 1 times) electric current is very big (average approximate number or so) , this electric current produces degauss magnetic field in degauss coil, undertake degauss to picture tube. In the meantime, as a result of voltaic fuel factor, make the temperature of degauss resistor rises quickly, after temperature achieves Courier to nod, its block cost rises quickly, make degauss loop assumes open circuit position. Actually, resistor of this kind of degauss had effect of a switch in degauss loop: Put through in power source the instant, this " switch " close, make degauss loop right color television degauss, degauss ends, "Switch " disconnect, make degauss loop quits the job.

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