The Dotronix BHD‑900 is a 9‑inch monochrome CRT display module used in industrial control panels and test systems. Common failure modes for this class of CRT monitors include power supply capacitor degradation, tube filament burnout, phosphor decay leading to image washout, and backlight or high‑voltage transformer faults that cause flicker or complete loss of picture. First‑check diagnostics: verify the 12 V/5 V DC supplies feeding the monitor, inspect the high‑voltage transformer for signs of overheating or leakage, and perform a visual inspection of the CRT tube for cracks or internal damage; if available, review any error logs from the host controller for related fault codes.[oss-gpt-20b]