BLANKING, MASTER GAIN, AND FAULT CIRCUIT, FUNCTION, DESCRIPTION.

 

 

SIMPLIFIED GAIN CONTROL CIRCUIT:

VIDEO INTERFACE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C5346

+12V

+

 

To

 

 

 

 

 

 

GAIN SELECT

 

Video

 

 

 

 

 

 

 

 

241

 

+12V

 

 

 

 

 

 

 

 

 

Amp.

 

CRT

 

 

 

 

 

RESISTORS

 

 

 

 

 

 

 

 

1K

MASTER GAIN

1K

VIDEO GAIN LINE

3.6K

200

Ω

+7.5V

 

 

 

 

 

 

 

 

 

 

 

 

485

 

 

 

 

062

 

 

 

 

One of three input circuits.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

HORIZONTAL BLANKING

PN2222

 

 

 

 

3

+3.4V

 

 

FLYBACK PULSE

 

 

 

 

 

FAULT CIRCUIT

 

 

 

 

 

 

 

 

 

 

 

 

 

1/4

 

 

 

0VDC

Hs

 

SIGNAL

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

56Vpp 62,D6

 

CONDITIONING

 

 

 

 

LM324

 

 

 

 

 

 

 

To P/S OVP

 

 

2

 

 

 

 

 

 

 

CIRCUIT

 

072

 

 

 

Total

 

 

 

 

 

 

 

 

033

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

beam current

 

 

 

 

 

 

 

 

 

 

BEAM CURRENT LIMITER

From FBT

 

 

 

 

 

 

 

 

 

 

High Temp. +12V

 

 

BIAS ACTIVE

VERTICAL BLANKING

 

+6V

 

 

 

 

 

HIGH Z +2.5V

 

 

6

 

 

MPSA64

 

 

 

Beam Limit

28.0K

 

 

 

 

 

 

 

 

 

1N4148

 

 

3

+

 

 

1N4148

1/2

 

7

PN2222

 

 

 

 

020

 

 

 

 

LM393

D

 

 

 

 

 

 

Vertical Bias O/S

1/2

1

 

253

 

 

 

 

 

 

 

 

5 +

 

 

 

+

 

 

018

 

100K

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LM393

 

 

 

210

 

036

 

10uF

 

T

+2.5V

2

 

 

 

 

 

 

 

 

 

@ 25°C

 

210

 

 

 

 

 

071

 

 

014

 

 

 

 

 

 

.047uF

 

 

 

 

 

 

 

 

180

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

207

 

 

 

 

 

 

 

 

 

 

Blanking in this monitor is accomplished by reducing the video gain to zero during the vertical and horizontal blank time. During video time, the gain is set by the master gain control which is located on the remote control PCB. If the overall beam current exceeds

.75mA or 1.5mA (depending on model) for more then ten frames, the beam current limiter circuit will reduce the video gain to protect the FBT. A high temperature sensor, close to the FBT, will also reduce the beam current if the high temperature limit (70°C) is exceeded.

The fault circuit senses the temperature or beam current line and will turn off the monitor if either of these signals exceeds the beam current shut off value. If an abnormal condition exists in the monitor or the cooling system of the enclosure fails, the high temperature sensor will activate the fault circuit at 80°C. The fault circuit is also turned on when the beam current becomes large enough to damage the FBT. This condition will happen if the video bias supply (V+ –9V) on the video board fails. An OP Amp. is used to sense the fault condition and a transistor is used to transmit the fault signal down to the power supply.

The video P-P voltage amplitude at the cathodes, is the video input signal amplitude times the master gain control setting times the video amplifier gain. The gain select resistors set the maximum video gain via the master gain line. For a greater range of brightness, (highlighting) the video system is allowed to supply high peak video currents which could damage the FBT if sustained. The beam current limiter circuit insures that the long term maximum beam current is not exceeded.

Horizontal blanking is achieved by amplifying the flyback pulse (FBP) with transistor 072 . Vertical blanking starts as soon as the LA7851 starts the vertical retrace sequence and is terminated by the auto bias, bias active signal. A comparator is used to sense the vertical bias O/S, at pin 16 of the LA7851, which goes low when vertical retrace starts. Capacitor 207 holds the vertical blanking active, between the vertical bias O/S pulse, and the bias active pulse. When the bias active line goes high, the capacitor 207 is reset and vertical blanking ends, after the bias active line returns to it's high impedance state.

75

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Page 59
Image 59
Genius 2793, ISO XFR-75W, 2093, 1493, 3693, 1793, 1993, ISO XFR-100W manual C5346
Page 58 Page 60

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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