Diagnosis of Malfunctions in Complex Electronic Assemblies. Final Report. Page: 38 of 66
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verifies correct fabrication by use of the aid and a general visual inspection
of these components and their connections. If the defects are component
failures, the assembler notes that C1, R1,or P1 are defective and gives the
unit to the troubleshooter who makes the final component fault isolation.
A photograph and a schematic drawing of the tester are shown in Figures 4
and 5. The schematic shows a. dual comparator which has adjustable limits
to detect correct logic-0 and logic-1 pulse amplitude levels. The following
gates accept either a negative or a positive pulse if these levels are met.
The pulse is shaped and applied to a counter which monitors 50 consecutive
pulses. If a sample of 50 pulses rheets amplitude requirements, a pulse-
width detector examines the width of the incoming pulse. The resolution
of the pulse width detector is approximately 70 nanoseconds. Indicator
lamps are activated for both accept and reject conditions.
Passive-Component Detector. This detector consists of a comparator type
of circuit. The original design considered three standards for comparison:
" Simulated components and networks;
* . A printed circuit board that had passed all inspection requirements; and
" Adjustable or programmable voltage limits.
The final tester circuitry used both of the first two types of standards. Some
modification was necessary if programmed voltage standards were to be
used. The simulated component or network standards were chosen for the
sake of simplicity and for the reason of economy. The same concept feasi-
bility would apply also to automatic or programmed comparator methods,
and modification required to adapt to this technique would be minimal.
The detector placs the component under test in series with the standard
and compares the total voltage across the standard with the voltage across
the component or network under test. The voltage across the standard is
one-half of the total voltage when components have the same value as the
standard. The voltage across the component under test is amplified by a
factor of two, inverted, and compared to the total voltage by a differential
corn.rator. The comparator is opened up with a strobe pulse and can be
strobed up at any time after the application of the driving function. The
driving function can be selected for the most ideal circuit response. This
extends the diagnostic capabilities of the detector by allowing some network
checks, as shown in-the following sketch.
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Losure, J. A. Diagnosis of Malfunctions in Complex Electronic Assemblies. Final Report., report, January 1, 1971; Kansas City, Missouri. (https://digital.library.unt.edu/ark:/67531/metadc1031893/m1/38/: accessed March 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.