Browse Prior Art Database

Video Amplifier for RGB Video Display Terminals (VDT)

IP.com Disclosure Number: IPCOM000038195D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Jackson, FS: AUTHOR [+2]

Abstract

Disclosed is a video amplifier design that can be automatically adjusted during the manufacturing alignment of a VDT.

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Video Amplifier for RGB Video Display Terminals (VDT)

Disclosed is a video amplifier design that can be automatically adjusted during the manufacturing alignment of a VDT.

The manufacturing of a VDT involves two basic processes. The first process involves some simple assembly; mounting a CRT in a bezel, mounting a card assembly and attaching a rear cover. The second process is the actual alignment of the front-of-screen (FOS) which includes the screen geometry as well as the color balance (making 'white' appear white).

This disclosure describes a 3-channel (Red Green Blue or RGB) video amplifier that can be adjusted electronically via computer control with the machine's covers installed. This is beneficial for manufacturing because it eliminates the task of manually adjusting potentiometers and allows field service personnel to make adjustments in the field without being exposed to hazardous voltages that are contained inside the box.

A conventional RGB video amplifier design requires a potentiometer to adjust the gain and cut-off of each video channel for a total of 6 potentiometers in all. This amplifier design utilizes Digital-to-Analog Converters (DACs) in place of the potentiometers. The DACs in turn drive transistor amplifiers that accomplish the gain and cut-off functions. The DACs are LSI modules that are compatible with the Philips I2C Bus, an inexpensive 2-wire bus that communicates with the manufacturing test equipment. This equipment includes a person...