*DRDY Signal Turned Off

What does 401 mean?

This alarm indicates that the *DRDY (Drive Ready) signal from the servo amplifier has turned OFF unexpectedly. The *DRDY signal is critical for indicating that the servo amplifier is powered up, healthy, and ready to accept commands from the Fanuc Series 20 CNC. Its loss means the servo system is not operational.

• Loss of control power (24VDC) to the servo amplifier.
• Internal fault within the servo amplifier (e.g., overcurrent, overvoltage, regeneration error, temperature fault).
• Loose or damaged control wiring between the servo amplifier and the CNC.
• Emergency stop engaged or other safety interlock active, deactivating the servo amplifier.
• Faulty servo amplifier.

Click steps to track your progress.

1. 1

   Check the servo amplifier's status LEDs for any internal fault indicators and refer to the amplifier's specific manual for their interpretation.

2. 2

   Verify all power supplies to the servo amplifier, including control power (e.g., 24VDC), are stable and present.

3. 3

   Inspect the control wiring connecting the servo amplifier to the CNC for loose connections or damage.

4. 4

   Confirm that no emergency stop or other safety interlocks are active that would disable the drive.

5. 5

   Reset the servo amplifier if possible and re-initialize the CNC. If the alarm persists and the amplifier shows no other specific fault, consider replacing it.