A diaphragm pump provides the airflow, controlled by a circuit that adjusts the motor speed via pulse-width modulation (PWM) or phase-angle control. Circuit Components and Common Failure Points Gordak 952-A Schematic Diagram | PDF - Scribd

If the unit is completely dead (no display, no fan), the primary fuse on the AC input is the first suspect. Following that, check the bridge rectifier and the main filtering capacitors in the PSU section of the diagram.

Q1‑Q4 (H‑bridge) ├─ OUT+ ----> Motor terminal A (J3) └─ OUT‑ ----> Motor terminal B (J4)