Spellman SL1200 is a compact high‑voltage DC power supply (up to 1 kV, 1.2 A) that uses a resonant high‑frequency inverter with proprietary control for efficient operation in transient and arcing environments. Common failure modes for this class include degradation of the resonant transformer windings, insulation breakdown on HV output leads, failure of the MOSFET driver or gate‑drive ICs, and overheating of the power stage due to inadequate cooling or over‑current conditions. First‑check diagnostics: verify input 220 VAC is within spec and that the unit’s main fuse/thermal cut‑out has not tripped; inspect HV output terminals for cracked insulation or loose connections; confirm the control IC and MOSFETs are at operating temperature and that the resonant oscillator voltage is within datasheet limits.[oss-gpt-20b]