The Lyman MK 4 Power Feed is a motor‑driven linear feed system used on Bridgeport milling machines, consisting of an AC drive unit, control panel, and mechanical linkage to the table. Common failure modes include worn or damaged gear teeth in the drive shaft, broken or misaligned linkages, electrical faults such as blown fuses or failed relays, and loss of power due to a defective motor or phase imbalance. First‑check diagnostics: verify that the unit receives proper line voltage and phase balance; inspect all wiring for continuity and secure connections; visually examine the gear train and linkage for wear or breakage; and review any error codes displayed on the control panel before proceeding with component replacement.[oss-gpt-20b]