The Quality Measurement Systems Gagemaster/GM4 Controller is a precision speed‑control module integrated into the GM4 optical comparator and measuring machine, providing regulated power to drive motors and sensor heads. Common failure points in this class of industrial controllers include burnt or tripped MOSFETs in the DC supply section, degraded heat‑sink connections, and worn capacitors on the input filtering stage; intermittent operation often indicates a loose I/O connector or faulty encoder interface. First‑check diagnostics: verify that the 12 V DC supply is within spec and stable, inspect all power and signal cables for continuity and secure terminations, and review any error codes displayed on the comparator’s readout panel for indications of over‑temperature or encoder faults.[oss-gpt-20b]