  Troubleshooting systems is integral to experimental physics in both research
and instructional laboratory settings. The recently adopted AAPT Lab Guidelines
identify troubleshooting as an important learning outcome of the undergraduate
laboratory curriculum. We investigate students' model-based reasoning on a
troubleshooting task using data collected in think-aloud interviews during
which pairs of students attempted to diagnose and repair a malfunctioning
circuit. Our analysis scheme is informed by the Experimental Modeling
Framework, which describes physicists' use of mathematical and conceptual
models when reasoning about experimental systems. We show that this framework
is a useful lens through which to characterize the troubleshooting process.
