Genius 2793 User Manual

RC4

483

482

486

500

Ω

750

Ω

1K

Vertical

Raster

Position

Vertical

Size

RC8

RC6

RC3

Remote Control Board

.1-.3VCD
3.8Vpp 17,E5

Vs

4-6VDC

2.8Vpp 18,D5

Vs

5.5-6.5V

1.4Vpp 23,F4

Vs

GND

18

17

GND

410

VERT.

OSC.

± SYNC INPUT

VERTICAL

VERTICAL

OSCILLATOR

OSC.  O/S

HEAT

SINK

378

362

365K

414

.01uF

361

127K

1

2

3

4

5

6

7

8

9

10

+12V

Ramp

Gen.

Slope

out

Vert.

Drive

Retrace

Booster

Drive

LA7838

Vertical

Deflection

004

510

Ω

375

401

1uF

380

470uF

388

392

391

393

68.1K

390

385

1.2

Ω

, 1W

403

V. osc.

363

203

0

Ω

V

377

CPC1058

.1uF

2.2M

ADJ.

V.+12V

376

100uF

+

5-6VDC

1.4Vpp 22,E5

Vs

V. size

Control

50/60Hz

5.5-6.4V

3Vpp 21,D5

Vs

One Shot

Tr.

R/C

out

374

.01uF

402

44.2K

Reset

Ramp

Reset

Ramp

369

1,000pF

+

+27V

VERTICAL DEFLECTION CIRCUIT DESCRIPTION.

Vs

VERTICAL SYNC

+12V SUPPLY

5.5-6.5V

1.2Vpp 19,D5

Vs

or

20

19

V+

VERTICAL

367

18

Ω

1N4005

382

H.+12V

VERTICAL

See

Table

     The vertical sync comes from the 
synchronized vertical sync interface 
circuit for monitors without interlace.   
For monitors with interlace the vertical 
sync comes from the sync comparator 
via a coupling capacitor and bypasses 
the synchronizing circuit.   Pin 19 of the
LA7851 is the vertical sync input and will
start the next oscillator cycle on either the
positive or negative sync pulse.   The vertical
oscillator capacitor  

410

   discharges to 4 volts

on the leading edge of the vertical sync by the
action of an internal transistor and resistor.
Capacitor   

410

  is then charged by resistor   

  

362

  until the next sync pulse or to 

8 volts, which ever comes first.   The V. osc.
frequency is set low such that the adjustment
resistor  

363   

can be used to act as a vertical

hold adjustment.   Solder connection  

V

   is

used to make this adjustment.

     The one shot in the LA7838 clamps the ramp
forming capacitor   

401

  to 5 volts for about half of

the vertical retrace time.   Capacitor   

374

  and

resistor   

402

  form the RC circuit for the ramp

reset one shot.

     The ramp capacitor   

401

  is charged by current

from a current generator with a 6 volt input node
at pin 4.   The vertical size is adjusted by the
vertical size control   

482

  which is connected to pin

4 via resistors  

 003

   &   

375

  .   The adjustment

range is set by resistor   

375

   and the maximum

deflection is set by resistor    

403

 .       A third input

to pin 4 comes from the vertical linearity circuit.
This circuit uses the above and below GND parts of
the vertical current waveform separately.
Transistor   

411

  conducts when the vertical current

waveform is below GND.   This transistor’s emitter
is referenced to GND by diode   

406

  and resistor 

  

371  

.   The emitter is connected to the vertical

current waveform through resistor   

407

  which is

adjusted for each tube and yoke combination.

80

     The vertical oscillator triggers the vertical
oscillator one shot, which outputs a pulse to
trigger the vertical sync input, pin 2, of the
LA7838.   This one shot is also used to
synchronize the CRT auto bias IC.   
Resistor   

361

  &   capacitor   

414

  set the 

timeout which must be longer than the CRT
auto bias Vs delay and shorter than the 
vertical blanking.   Resistors   

370

  &   

408

supply the pullup for this one shot.

362

370

408

414

361

363

403

384

003

402

407

371

411

375

406

410

482

410

401

375

401

V