Johnson Fitness SDH‑T100 is a treadmill motor‑control board that manages speed, torque and safety interlocks. Common failures include failed MOSFETs or driver ICs causing the motor to refuse to start while lift functions remain intact; power supply voltage drops or shorted phase leads also trigger similar symptoms. For this unit, first verify the 48 V DC rail is within spec and check for any blown fuses or tripped breakers on the board’s power input. Next inspect the MOSFET array and driver ICs for discoloration or overheating, then confirm that the motor‑drive current sense resistors are intact. Finally review the error log (if available) for “motor not started” codes to pinpoint a specific fault.[oss-gpt-20b]