I got a Quincy QR25 that had a continuous-run motor and totally pneumatic pressure controls. I swapped in the largest motor the compressor was rated for, changed the motor pulley, and built a microcontroller "automatic dual mode" controller for it. Once it reaches the pressure on the pressure switch, the compressor in unloaded, and the motor continues to run for 30 seconds. If I need air again within that time, it just shuts off the unloader. If not, the motor is stopped. It also unloads the compressor for motor starting, and watches the oil pressure. See
Yeah, I've got some leaky regulators to either repair or replace.