Standards teach you how the system works. The field teaches you how it breaks. This is a growing library of real troubleshooting cases — the symptom, the investigation, the root cause, and the lesson — written by the techs who lived them.
About the labels. Cases marked Composite are training scenarios built from standards-grounded concepts — realistic, but not records of a specific incident. Cases marked From the Field are real, contributed by a named technician. The library starts with composites to show the format; the real cases are what make it irreplaceable.