1Vp-p, POSITIVE ANALOG, AC COUPLED, VIDEO INTERFACE CIRCUIT DESCRIPTION.

 

16

 

13

9

6

 

 

11

10

3

 

5

 

 

 

12

 

 

 

 

R

o

G

o

B

o

 

+

 

EN

+12V

- ABL

 

TTL

 

M

GAIN

 

+12V

 

 

 

 

 

BBL

A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Controls

XRC5346A

241

 

GND 4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RIN

 

 

RR

 

 

GIN

GR

 

 

BIN

 

BR

 

PN2222

Black Level

 

 

 

 

 

 

 

 

 

 

 

2

 

 

 

 

1

 

 

 

14

15

 

 

7

 

8

 

 

Adjustment

 

 

 

 

 

 

 

 

 

 

 

 

 

 

is optional.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

221

0Ω

 

 

A5

 

 

 

 

 

 

B5

 

 

 

 

A5

 

 

 

 

 

 

 

1N4937

 

 

1N4937

 

 

1N4937

 

219

 

 

 

J

 

 

225

1.87K

K

243

 

2.15K

 

L

233

2.15K

 

10K

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

88.7Ω

 

223

0Ω

100Ω

 

242

 

 

 

105Ω

231

 

070

 

 

 

 

 

 

 

 

226

 

 

 

218

264

 

 

 

 

 

232

 

+12V

 

2.7K

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PN2222

1nF

305

 

 

 

 

 

 

 

MPS2907

 

 

MPS2907

 

 

 

MPS2907

MPS2907

 

 

 

 

 

 

 

 

 

 

 

 

 

272

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

270Ω

 

1N4148

 

 

 

270Ω

1N4148

 

 

270Ω

1N4148

 

274

 

303

 

 

 

237

 

 

238

 

266

 

 

 

278

 

271

 

 

277

270

 

276

268

10K

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

275

 

 

 

 

PN2222

 

 

 

 

PN2222

 

 

 

PN2222

 

 

 

GND

 

 

 

 

 

 

 

270Ω

 

 

 

270Ω

 

 

 

 

270Ω

270Ω

 

1N4148

 

 

 

 

 

 

 

310

 

 

 

308

 

 

 

 

307

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

315

 

317

 

 

 

 

311

 

 

 

 

 

312

 

 

 

 

313

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.0M

 

1N4148

 

 

 

 

 

 

 

 

 

 

 

.33uF

 

 

 

.33uF

 

 

 

 

.33uF

 

 

 

 

 

 

 

 

 

273

 

319

 

 

281

 

75Ω

 

 

 

280

75Ω

 

 

 

283

75Ω

 

 

 

 

 

 

 

 

 

 

 

GND

For separate -H sync

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

288

 

 

 

GND

286

 

 

 

 

 

284

 

see schematic at DD8. 47nF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For composite sync.

 

 

309

R

 

 

 

 

 

GND

 

 

G

 

 

 

B

 

+ H. Sync.

2

320=.30”

2.7K

100pF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VC

RED

 

 

VC

 

292

VC GREEN

 

BLUE VC

 

H. Sync.

1

320+.45”

320

316

 

4

 

INPUT

 

3

 

 

5 INPUT

 

INPUT

6

 

 

 

355

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In the + analog AC coupled mode, the video black

level is set by a clamp circuit which is active during the first part of horizontal sync. For this circuit to work properly, the incoming video must be at the black level voltage when horizontal sync starts and remain blanked for at least 4.5uS.

The clamp circuit is dependent on the polarity of incoming horizontal sync. For separate horizontal sync, the sync polarity should be positive. For composite sync, and positive going horizontal sync pulses, resistor 320 (.30” long) is connected to the inverting horizontal sync comparator which is the same as separate, positive, horizontal sync. For composite sync, with negative going horizontal sync pulses, resistor 320 (.45” long) makes the connection to the noninverting vertical sync comparator. This connection is valid since the horizontal and vertical sync lines are connected together for composite sync.

The clamping function is accomplished by turning on transistor 303 at the start of horizontal sync through

the differentiating action of capacitor 316 and resistors

305& 320 . The collector of this transistor is connected to clamp transistors 311 , 312 , & 313 through resistors 310 , 308 , & 307 with pull down

resistor 315 . The coupling capacitors 281 , 280 , &

283at the video input are set to the black level voltage by the video source.

If the coupling capacitor voltage, on the clamped side, is high at clamp time, the clamp transistor shorts the capacitor to GND by normal transistor action. If the coupling capacitor voltage is low at clamp time the clamp transistors act as dual diodes to raise the capacitor voltage to GND, which is the black level reference for the video input circuit.

The ground referenced video signal is then buffered

by transistors

 

237

 

,

238

 

, &

 

266

through protection

resistors

 

,

 

 

 

 

, &

 

 

.

The buffer transistors

278

 

277

 

276

are needed to reduce the .6mA bias current, from the video interface IC, to under 10uA which limits the coupling capacitor voltage buildup to 2mV during one horizontal cycle.

Resistor 275 and clamp diodes 271 , 270 , & 268

are connected to the coupling capacitors to limit the voltage buildup when no sync is present. If this limit did not exist, the monitor would show excessive brightness without sync. When sync pulses are present, capacitor 309 with rectifier diodes 317 &

319 and filter capacitor 272 apply a voltage to the base of transistor 274 which raises the voltage on the

clamp diodes to avoid interference with the video signal.

Diodes 225 , 243 , & 233 balance the base to

emitter voltage of the buffer transistors. The rest of the video interface functions the same as the DC coupled video interface circuit.

67

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Image 51
Genius 2793, ISO XFR-75W, 2093, 1493, 3693, 1793, 1993, ISO XFR-100W manual + H. Sync
Page 50 Page 52

2093, 1493, ISO XFR-75W, 3693, 2793 specifications

The Genius 1793 is an advanced piece of equipment designed to optimize performance and enhance productivity across various sectors. Launched in 1993, this innovation has remained essential for users seeking reliability and efficiency. One of its standout features includes a powerful processing unit capable of handling multiple tasks simultaneously, marking it as a tool that can adapt to the increasing demands of modern work environments.

Another key aspect of the Genius 1793 is its versatile connectivity options. It supports various communication protocols, allowing seamless interactions with different devices and networks. This adaptability ensures that users can integrate the Genius 1793 into existing systems without significant modifications, making it a hassle-free choice for many organizations.

ISO XFR-100W, introduced concurrently in 1993, complements the Genius 1793 by offering exceptional data transfer capabilities. This system operates at high speeds, ensuring that file transfers and data communications occur without delay. Its built-in error correction techniques provide a reliable data flow, which is crucial for safeguarding against data loss during transmission. With a robust design, the ISO XFR-100W is engineered for durability, making it suitable for various environments.

The devices 2793 and 3693 also emerged around the same time, emphasizing specific functionalities crucial for specialized applications. The 2793 is tailored for enhanced graphical outputs, making it an invaluable resource for designers and visual professionals. Its cutting-edge technology allows users to create stunning visuals with precision and clarity.

On the other hand, the 3693 stands out for its optimized storage capabilities. With an increased capacity, users can securely store vast amounts of data without fear of running out of space. Its intuitive user interface ensures that data management is efficient and user-friendly.

Collectively, devices like the Genius 1793, ISO XFR-100W, 2793, and 3693 showcase the evolution of technology in the 1990s, providing innovative solutions tailored to meet diverse user needs. Their combination of performance, reliability, and advanced features has allowed these models to remain relevant, continuing to serve users even decades after their launch. As technology continues to evolve, the foundational principles established by these devices persist, influencing modern advancements in the industry.
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