For the C stepper drive, the OEM750 would be the recommended replacement stepper drives. The E-DC would be recommended if using 24-48vdc to power the C drive.
For the CX programmable stepper drive, the OEM750X would be a very close replacement. The CX was a unipolar drive. The OEM750X is a bipolar drive, so the motor could be rewired in series.
For a bipolar series drive, multiply the current of the unipolar motor by 1.414 to find what the OEM750/E-DC/OEM750X should be set to and wire the motor in series. The C series motors are compatible with these drives. As a reference:
Unipolar and Bipolar Motors FAQ
The C and CX had a maximum 90vdc input, 5A per phase output. The C and CX could be powered by the DC3 (90vdc).
The OEM750/OEM750X has a maximum 75vdc input. If needing a power supply, the OEM300 is a 300watt 75vdc power supply, good to power 2 or 3 OEM750/OEM750Xs.
The OEM750X uses the same X programming language to the CX, though there were improvements from the CX to the OEM750X.
The OEM750, E-DC and OEM750X have anti-resonance circuitry built-in. In addition to the bi-polar change, there's an estimated 10-20% increase in motor shaft torque.
The above replacement recommendations are based on product specifications. These recommendations should give a very close product replacement but are implied as a true dropin replacement. Sometimes not all features or performance of a product are being used in an application. Application requirements can be reviewed by the local Parker ATC for a more detailed system analysis and product recommendation.