LA76931 データシートの表示（PDF） - Unspecified

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LA76931

64Pin LA76931 for Color Television Receiver / SERVICE MANUAL

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A) +B is high

+B

Vb of V553

Ic of V553

Resistance of N501

Ib of V511

6

Ic of V511

B) +B is low

+B

+B

V 513 turn off

Ib of V513

Ic of V512

Ib of V512

Vb of V553

Ic of V553

Resistance of N501

Ib of V511

Ic of V511

+B

V 513 turn on

Ib of V513

Ic of V512

Ib of V512

Chapter Two Horizontal Deflection

2.1 How does the horizontal deflection circuit work

Although there are many variations, the basic operation of the horizontal deflection /high voltage power supplies in most Tvs, and other CRT

displays is very similar.

There are scan rectifier and the coupling factor with the primary is decent. But they make no use of the stored magnetic energy, they load the primary

directly during the scan part. They do not cause an increase of the stored magnetic energy so a heavy load is not a problem. The flyback rectifiers ( esp.

the EHT) draw from the stored magnetic energy. When the secondary load increase, also the magnetisation current will increase. Ultimately this will

cause saturation of the ferrite core. Excess beam current is a common cause for this and should be avoided by the beam current limiter. The advantage of

a flyback rectifier is that it provides 7 times more volts per winding than a scan rectifier.

+B

Scan

+V1

+B

Flyback

+HV

Rectifier

Rectifier

HOT

HOT

Here, V1 is just a typical example of an auxiliary supply derived from a scan rectifier and HV is the best known example of use of a flyback rectifier.

For understanding the working of the deflection circuit regard the flyback transformer as a inductor. The air gap stores energy, some of which may be

tapped off during flyback by secondary rectifiers(e.g. Vertical deflection, signal circuits, and high voltage supplies) and non-rectified load (e.g., Filament

supply) but these have hardly any influence on the basic working principles.

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