Diagnosis of Malfunctions in Complex Electronic Assemblies. Final Report. Page: 20 of 66

Figure 1 categorizes over 1600 failure causes and assigns a complexity
code based on the skill required to perform the troubleshooting task.
" "S"T is used as a symbol for the least complex category. Failures falling
in this category require a small amount of knowledge of the overall
function and only a general knowledge of individual circuitry.
" "A" represents a category that requires a sound understanding of the particu-
lar overall circuit function and an average knowledge of detail circuitry and
electronic fundamentals.
" "C" represents a category defined as complex, and demands detailed
analysis of waveforms and general circuit operations. This type of
analysis requires a thorough knowledge of theory and troubleshooting
" "E"r represents those categories that require engineering skill. All
problems that involve design discrepancies in assemblies or components
and any diagnostic problems requiring a mathematical or technical back-
ground of an engineering nature are examples of this category. This
assumes that the diagnostician had not seen the problem before
Diagnostic Equipment Automation. The necessary skill level of the trouble-
shooter is dependent on the extent of the automatic analysis that can be done
by the diagnostic test equipment. Although analytical and diagnostic equip-
ment is considered in detail in Phase 2 of this report, general consideration
of this subject was necessary so the operator skill level could be defined and
equipment that would be compatible with that skill could be developed.
The techniques of self-check and computer-type analysis for diagnosis of
electronic malfunctions, as done in large permanent radar or computer
installations, are not directly applicable to troubleshooting procedures used
in a manufacturing plant where the plant mission involves the manufacture
of military products with a great variety of designs, relatively short
production runs, state-of-the-art designs, stringent reliability requirements,
and emphasis on reduced size and weight.
The size and weight restrictions prevent self-check type circuitry from being
built into the unit circuitry. Circuit nodes are very close together in minia-
ture and microminiature assemblies, making parallel fixturing pickup of all
nodes necessary for troubleshooting and analysis more complex than in
larger assemblies.
Fault diagnosis by computer methods was considered, but was not pursued
past the preliminary planning stage for the following reasons:
" High cost of initial equipment;


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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/m1/20/ocr/: accessed April 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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