That reminds me of the troubleshooting charts found in some technical manuals. It never is complete, and you could end with, this is an unlikely event statement. I can remember a Rogowski coil failing to produce the proper amplitude feedback which resulted in the "unlikely event" statement in the service manual.That brings the question: is running down a really complete SELECT CASE statement the same as looking at a problem and troubleshooting it? I've seen stuff that made no sense at all. The intelligence part comes in persisting and finding the problem even though the symptoms do not point at the cure.