Philips Colour Television Specifications download pdf (Page 51)

Circuit Descriptions and Abbreviation List

GB 103EM3E 9.

9.10 Horizontal (Line) Deflection (diagram A3)

9.10.1 Principle

Figure 9-9

The HOP (located on the SSB) generates the line-drive

pulses (LINEDRIVE1), which have a frequency of 31250 Hz

(T = 32

ms).

When the LINEDRIVE1 signal is high, TS7409 and TS7408

will conduct. A constant DC voltage will be applied across

L5410, causing a linear increasing current through this coil.

The secondary voltage of L5410 has a negative polarity so

that TS7421 will block. When the set is switched ‘on’,the

current through L5410 is supplied by the 5V2 Standby supply

(via D6407), and taken over by the +11D voltage (via D6408)

of the main supply.

When the LINEDRIVE1 signal becomes low, TS7409 and

TS7408 will block. The voltage polarity across the primary

winding of L5410 will invert. The positive voltage on the

secondary winding will now drive TS7421 into conductivity.

Because of the storage time of the line transistor (TS7421),

L5410 cannot transfer its energy immediately to the

secondary side. This may result in high voltage peaks on the

collector of TS7409 and TS7408. To prevent that these

peaks will damage the transistors, a 'snubber' circuit (C2414,

C2412 and R3411) will suppress them.

When the LINEDRIVE1 signal is high again, the above

described sequence starts again. Circuit L5411 and R3409

will increase the switch ‘off’ timeofthelinetransistor.

The line stage is started via a 'slow start' principle. During

start-up, the HOP generates line drive pulses with a small

and a high frequency (50 kHz). T

OFF

is constant and T

is gradually increased until the frequency is 31.25 kHz

(normal condition).

The time interval from start to normal condition takes about

150 ms.

When switching off, the same procedure is followed, but now

in reverse order.

9.10.2 Implementation

To explain the operation of the line output stage, we use the

following start conditions:

• C2433 is charged to max. 141 V (V

BAT

)

• TS7421 is driven into conductivity.

CL 16532044_018.eps

140501

3481

6480 2426 6422

2421

7480

ARC

PROT

3414

2415

6406

3406

3431

2430

1417

5421

2431

141V

7482

3418

3488

HOTCOLD

2425 6423

2432//33//34

6408

6407

3416

3409

5411

2414

5410

3411

2412

7408

+8VB

+8VS

7409

MAIN SUPPLY +11D

STANDBY SUPPLY +5V2

2492

3407

3487

2420

7421

5430

2417

3417

3486

3412

6615

3404

LINEDRIVE 1

(HOP)

EW_DRIVE

(HOP)

STARTNORMAL

T7421 conducting

OFF

(*1)

(*2)

LINE

DEFL. COIL.

LINEARITY

COIL.

5422

Caused by

serial losses in

the line output stage

Linearity Correction

S-correction

Deflection centre

X > Y

7450-B

3490

3484

3492

7487

7486

3483

3479

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Philips Colour Television Specifications Page 51

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