Granville‑Phillips Series 270 Gauge Controller (model 270004‑1) is an ionization gauge controller used to supply regulated high‑voltage bias and read the output from vacuum gauges in industrial vacuum systems. Common failures on this unit include power‑supply tripping due to overcurrent, insulation breakdown between the high‑voltage output and chassis leading to arcing, and failure of the internal microcontroller or display circuitry after prolonged exposure to plasma‑induced contamination. First‑check diagnostics: verify that the AC input voltage matches the specified range (120–277 V) and that the controller’s power supply is delivering correct DC rails; inspect all exposed conductors for proper grounding and look for burn marks or corrosion on connectors; review any fault codes displayed on the panel or logged in the serial‑port interface.[oss-gpt-20b]