In this article, we explore the diagnosis and repair of common failures in the XTR116UA/2K5 4-20mA current loop. This sophisticated instrumentation plays a critical role in measurement and control systems, and understanding how to identify and fix problems with this component is essential for maintaining the reliability of industrial systems. Part 1 covers the basics of the XTR116UA/2K5, common failure modes, and initial troubleshooting steps, while Part 2 delves into advanced repair techniques and best practices for prevention.