Browse Prior Art Database

Display Linescan Detector for Time To Failure Tester

IP.com Disclosure Number: IPCOM000122479D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 115K

Publishing Venue

IBM

Related People

Knox, AR: AUTHOR

Abstract

This disclosure relates to a useful low-cost tester of CRT displays in a thermal test manufacturing environment. Gross failure of a linescan of a display on test is detected by this device. An embodiment of this detector is described in the preceding two articles.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Display Linescan Detector for Time To Failure Tester

      This disclosure relates to a useful low-cost tester of
CRT displays in a thermal test manufacturing environment.  Gross
failure of a linescan of a display on test is detected by this
device.  An embodiment of this detector is described in the preceding
two articles.

      A test system exists to provide time to failure data. It
consists of four major parts: the detectors used in the test chambers
(to which this disclosure relates), 16 channel receiver cards, a bus
interface and control card and software to drive the tester.  The
software is written in 'C' and runs on an IBM PS/2* mod 70.

      The detector picks up the electric fields associated with a
working display at the faceplate of the CRT.  At this stage the
signal has a very high impedance and is buffered by a FET input
OP-AMP with gain.  Also connected to the input of this amplifier are
self-test circuits.  After the signal has been buffered, it is
rectified by a full-wave rectifier based on a pair of OP-AMPs.
Full-wave rectification is required for two reasons:
1.  A prototype of this system generated false display status when
more than about 30 displays were connected simultaneously, due to
crosstalk between channels by unsynchronized displays.  Now, only DC
signals are transmitted with no crosstalk problems.
2.  The varying component of the detected signal is due predominantly
to the field associated with linescan.  This can be either positive-
going (most usual) or negative-going as in IBM's 8515 display.
If only half-wave rectification were used on a product such as 8515,
there would be no distinction between ON and OFF. The output from the
rectifier is peak detected, smoothed and fed to a Schmitt trigger
with a few volts of hysteresis. This operates such that the presence
of linescan or otherwise causes the output signal to switch between
+12V and -12V, connected via underfloor cabling to the main part of
the tester.

      The detector has a bidirectional indicator fitted on its output
such that RED corresponds to OFF and GREEN corresponds to ON.  The
detector circuit board is held inside a small plastic enclosure with
the indicator protruding.  Detectors were taped to the screen of the
display which is not suitable where many displays have to be
connected in a short time period.  The detector enclosures are now
attached by means of rubber suckers to the faceplate and are capable
of supporting the detector and associated cable for the duration of...