Quinton VSD 031225‑001 is the main control board for Quinton treadmill and club‑track models (e.g., TM‑55/ST‑55). Typical failure modes on this 15+ year‑old PCB include burnt or cracked power MOSFETs, degraded electrolytic capacitors, and loose or corroded I/O connectors that can cause intermittent motor control or error codes. First‑check diagnostics: verify the input voltage to the board (24 V DC) and ensure all supply rails are within spec; inspect for visible damage on power components and check for blown fuses or burnt tracks; review any displayed error codes against the treadmill’s service manual, then test I/O signals with a multimeter or oscilloscope before proceeding to component replacement.[oss-gpt-20b]