Genius 2093, ISO XFR-75W, 1493, 2793, 3693, 1793 CRT TC12, Socket Board, CRT Auto Bias, Bright

5.6V to 1.1V, NEGATIVE ANALOG, DC COUPLED, VIDEO INTERFACE CIRCUIT DESCRIPTION.

SOCKET BOARD

0VDC Hs

Red Video Amp.

Beam current

56V

28,D3

800

Feedback

Beam current

TC11

Filament

Green Video Amp.

CRT TC12

Fil. Ret.

Feedback

Beam current

Screen

Blue Video Amp.

Focus

Feedback

ARC PROTECT

FIL.

EHT

HSync

B+G+R=

∑

Beam

127V TC8

+127V

Auto

GND

+12V

+16V

CRT Auto Bias

Buffer

Current

V Sync

ABA

Bright

TC2

TC4

TC1

+16V

TC7 Red

TC 10

TC 6

SOCKET BOARD CONNECTOR (TC)

206

+12V

TC5 Green

End Vertical Blanking

+

TC 3 Blue

Vertical O/S or Delayed Vertical O/S.

100uF

209

GND

Blanking & Beam Current Limit

S

VIDEO GAIN

Remote

T

U

FDH400

LINE

1K

Control PCB

1.62K

604Ω

1.21K

1.62K

4-7VDC Vs

062

+12V

084

5-9Vpp 61,B4

M. GAIN

FDH400

260

244

245

076

RC2

1K

2.7K

485 GND

1.21K

086

064

+12V

258

+12V

11.5V-12.5V

FDH400

GND

213

P

G

0Ω , CS=.30"

0Ω

+ 100uF

Note:

271

4.7K

The clamp

228

293

267

diodes are

270

16

13

9

6

239

11

10

3

5

12

12V

installed

268

Ro

Go Bo

+AEN

+12V

-ABL

TTL

MGAIN

backwards with

VC

BL

241

0

respect to the

B

Controls

XRC5346A

PCB legend.

GND 4

+12V

RIN

RR

GIN

GR

BIN

BR

PN2222

3.92K

2

1

14

15

7

8

272

3.5V

340Ω

1N4148

340Ω

1N4148

301Ω

1N4148

274

271

270

268

236

218

266

1K

2.15K

275

273

301Ω

340Ω

301Ω

278

277

GND

276

R		GND		Video	G			B
			Connecter
VC	RED	VC			VC	GREEN	BLUE	VC
4	INPUT	3		292	5	INPUT	INPUT	6

In each of the video interface circuit configurations, current from the interface circuit is converted to a voltage at the CRT cathodes. The simplest current path is accomplished by the negative analog video interface configuration.

The voltage drop across the input resistors 278 and

236, for the red channel, is the current which drives the video amplifiers when the video gain line is at

8.2volts. For a lower gain line voltage, part of the current is directed to the +12 volt line. During blanking all the input current flows to the +12 volt line.

and there is no video amplifier output. For the red and green channels, a 1 volt change at the video input produces a 15 volt change at the video amplifier output. For the blue channel this change is 18 volts but resistor

265subtracts the equivalence of .6 volts from the input which results in the same saturated color as the red and green channels.

The clamp diodes 271 , 270 , & 268 limit the maximum current to the video amplifiers. This avoids over driving the video amplifiers when undershoots at the input cables are present. The clamp reference

voltage is set by resistors			272	,	273	, and buffer
transistor						stabilizes this
	274	. Load resistor			275
buffered clamp voltage.

65