Genius 1993, ISO XFR-75W, 2093, 1493, 2793, 3693, 1793, ISO XFR-100W manual

DYNAMIC FOCUS CIRCUIT FUNCTION AND CIRCUIT DESCRIPTION.

Model 1793-31.5DF

NO DVM Hs

.8KVp-p 27,G6

FLYBACK

CRT

Horizontal Drive

10

TRANSFORMER

EHT

Transformer

Grid.

Wire.

Wire.

CPT1505

1/2W, CC

G1

2

332

13

470Ω

433

520

Screen

White

Red

3

1N4007

V+

0Ω

9

FOCUS

1

4

435

452

#2 FOCUS

1.2Ω

SCREEN

12-18VDC Vs

H PLL

8

434

12 Dynamic Focus

DM Drive

50Vpp 29,F6

11

0Ω

GND

7

4

465

YC1

OVP

5

P/S Sync

Beam Current

426

VERTICAL

3

1,000uF

DEFLECTION

V-

1

2

Filament

35V

Vs

YC2

YOKE

+

CPT1555

453

GND

427

449

V+

2,200pF

1N4007

13-15VDC Vs

1KV

HORIZONTAL YOKE

3-5Vpp 31,F5

Vs

2.2MΩ

2.2MΩ

507

512

1.00MΩ

510

511

0VDC

Vs

504

200KΩ

1

CPT1556 2

1.6Vpp

2SC3467

Horizontal

.33uF

514

1KΩ

509

0.1uF

Linearity &

501

4

3

250V

270Ω

Width coils.

500

518

.47uF

.01uF

0Ω

330pF

516

.47uF

1.2Ω , 1W

191K

36K

Hs

517

200V

1.6KV

385

502

503

505

500V

443

444

441

515

GND

Horizontal Width Control.

(Diode Modulator)

The dual focus CRTs require a waveform on the #2 focus grid. This voltage waveform is dependent on the position of the beam on the CRT. The lowest voltage part of the waveform is in the center of the screen and the highest voltage part of the waveform is at the corners of the screen.

The dynamic focus circuit produces a composite waveform which consists of the horizontal parabolic waveform and the vertical parabolic waveform. This composite waveform is applied to the dynamic focus input, of the flyback transformer, and produces a sharp picture on the dual focus picture tubes. Typically dual focus picture tubes produces a sharper picture than the single focus picture tubes.

Dynamic Focus Circuit Operation: The vertical component of the dynamic focus circuit is derived by amplifying the voltage waveform across the vertical yoke coupling capacitor. The horizontal component of the dynamic to focus circuit is produced by applying the voltage waveform across the horizontal yoke coupling capacitor to the dynamic focus transformer primary. This transformer steps up the horizontal parabolic voltage from about 33V to about 300V to produce the horizontal component of the dynamic focus circuit.

Circuit Description: Transistor 509 amplifies the vertical parabolic waveform which exists across capacitor

449 . This waveform is coupled to the transistor base via capacitor 500 and resister 501 . The bias for this transistor is generated by resistors 503 and 504 . The gain of this amplifier is defined by resister and 505 .

Note; Resister 505 is connected to the vertical feed back line and not to ground. The supply voltage for the collector is produced by diode 512 which rectifiers the primary flyback pulse and is integrated by capacitor 507 .

The load resisters for this transistor are resistors	510	and	511		.	The waveform on the collector, which is the
vertical parabolic waveform, is conducted through resister						and through transformer		to the dynamic
			514				518
focus input of the flyback transformer. Resisters		and				provides arc protection for transistor				. The
	514			501					509

horizontal component of the dynamic focus waveform is produced by coupling the primary of the dynamic focus transformer at 518 to the horizontal yoke coupling capacitors at 443 and 444 . Capacitor 515 provides a low impedance pass to ground for the horizontal parabolic waveform which is developed across the dynamic focus transformer secondary at 518 . Capacitor 517 insures that there is no D. C. component across the transformer primary. Resister 516 protects the dynamic focus transformer primary from overload.

The flyback transformer 453 couples the dynamic focus waveform to the #2 focus grid via an internal capacitor.

86