The Tracor Westronics 85J561001 is a strip‑chart recording unit used to log process variables via analog input and display them on a built‑in screen or output to external devices. Common failure modes in this class of equipment include power supply board faults (brownouts, capacitor failures), signal conditioning module degradation (input amplifier drift or clipping), and drive motor or stepper issues that prevent the chart head from moving correctly. First‑check diagnostics: verify 24 VDC/AC input voltage and regulator output; inspect the main PCB for burnt components or loose solder joints; test the analog input range with a calibrated signal generator and confirm the display responds to known inputs.[oss-gpt-20b]