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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum ( )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Posted by: John ( )
Date posted: Fri Jan 25 15:36:43 US/Eastern 2002
Subject: Unconfirmed Field Failures
When testing returned units (i.e. circuit cards) that have failed at customer sites, occasionally the reported failure or any failure can not be duplicated. Is there any information or rule of thumb regarding these unconfirmed field failure rates? I would be interested in any opinions or experiences.

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Subject: Unconfirmed Field Failures
Reply Posted by: John Turnbull
Date Posted: Fri Mar 15 5:55:30 US/Eastern 2002
I would suggest looking at the other components in the system. Could something, other than the returned component, have failed but in replacing the returned component been fixed. i.e. resetting system parameters. In power generating systems you can find that the generator trips the control unit off-line but because its "easier" to replace the control unit thats what the technician does. So where the generator caused the fault the control unit is sent back to base faulty and when tested is found to be an unjustified removal (NFF). We find this happens a lot. The easier an LRU is to remove the more NFF returns arise. Again, just a thought.

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