Diagnosis of Malfunctions in Complex Electronic Assemblies. Final Report. Page: 31 of 66
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Phase 2 Development
Phase 2 work was concerned with the development of diagnostic equipment
and processes that would improve isolation. Four general categories of
testers were chosen for evaluation because they were expected to yield
significant economic and quality benefits if development efforts proved the
concepts feasible. The four types of testers are:
" In-process verifiers;
" Special diagnostic testers for electronic subassemblies;
* Diagnostic testers for the evaluation of components; and
e A product simulative-type tester.
The application and testing concepts associated with each of these testers
are discussed in the following paragraphs.
Concept Number 1. One method of simplifying the diagnostic problems
resulting from manufacturing errors and component failures is to evaluate
individual components or component networks by in-process testing at
selected stages of the fabrication of printed circuit hnarrl assemblies. A
component failure or a manufacturing error which causes only subtle changes
in output parameters can be difficult to isolate by functional-analysis methods.
This is particularly true if the assembly has a large number of components
or contains circuitry with complex feedback loops which make rircnit parame-
ters highly inter-related. For example, a fault in almost any stage of an
oscillator-type circuit or an AGC loop can disable the overall circuit function
and add to the difficulty of isolation by functional methods. The expected
advantages of isolating faults at the time of assembly by checking individual
components or component networks were: rapid feedback to the production
line; simplification of diagnostic problems caused by assembly errors and
initially-bad components; simplifying the isolation of more than one fault
in an assembly; and a more thorough check of components on the board.
Concept Number 2. The second tester concept chosen for development was
a special type of diagnostic tester with a design oriented toward diagnostic
capabilities rather than testing.
The typical inspection tester necessarily automates operator control and
influence out of the testing process. This is especially true in testers de-
signed to test military products that require permanently stored data that
is to be used for reference to determine environmental degradation. These
testers are often required to meet state-of-the-art accuracy requirements
which are seldom required to detect fabrication errors and faulty circuit
components, since a very high percentage of these errors result in significant
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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/m1/31/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.