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Check available disk space

Press MOD key → System Settings → Display System Information → check SYS: partition free space. The system requires minimum 50-100MB free space for proper operation.

On iTNC 530 and TNC 620/640, you can also check disk space via PLC → Settings → System Information → Memory.

Delete unnecessary files

Navigate to File Management (PGM MGT key) → TNC:/ directory → delete old log files from TNC:/log/ directory, unnecessary backup files (*.bak), or old program files that are no longer needed.

Do not delete system directories or files you did not create. Only remove user-generated content or dated log files.

Archive programs to external media

Transfer large NC programs or unused part programs to USB storage or network drive to free up space. Use File Management → Copy function to move files externally.

Regularly maintain disk space by archiving completed jobs to external media as part of preventive maintenance routine.

Restart control after cleanup

Perform a controlled shutdown (MOD → Shutdown) and restart the control to allow the system to recreate backup files with sufficient space now available.

Power down the control

Perform a proper shutdown sequence via MOD key → Shutdown. Wait for the control to completely power down before proceeding.

Always perform controlled shutdown before accessing CF card to prevent file system corruption.

Inspect CF card write protection

Open the CF card access door (location varies by control model - typically on front panel or side of control unit). Check the small sliding switch on the CF card side - it should be in the unlocked position (away from 'LOCK' marking).

Mark the correct switch position with a label or photo for future reference, as the switch can be accidentally moved during maintenance.

Reseat the CF card

Remove the CF card completely, inspect for physical damage or dirt on contacts, clean if necessary with compressed air, and firmly reinsert ensuring full seating with audible click.

Handle CF card by edges only. Do not touch gold contacts.

Restart and verify

Power up the control and allow full boot sequence. The alarm should clear if write protection was the cause. Verify by making a minor configuration change to test backup functionality.

Check system error logs

Access MOD function → System Settings → Error Messages → Display Error Log. Look for file system errors (FS errors, mount errors, or I/O errors) that occurred prior to the backup alarm.

Note the timestamp and exact error codes - these are valuable for Heidenhain service diagnostics.

Perform controlled restart

Execute proper shutdown via MOD → Shutdown, wait 30 seconds, then power up. The control may automatically run file system checks (fsck) during boot. Allow this process to complete without interruption.

Do not interrupt file system check during startup - this can worsen corruption. The boot process may take 5-10 minutes.

Boot into service mode

If alarm persists, boot into service mode by holding MOD key during power-up. This provides access to file system utilities. Navigate to System Diagnostics → File System Check and run verification.

Service mode access may require service password on some control versions. Contact Heidenhain if access is restricted.

Run file system repair

In service mode, select File System Repair option. This runs fsck utility to check and repair file system inconsistencies on the SYS: partition. Follow on-screen prompts and allow completion.

File system repair should only be performed when machine is idle. Backup critical data first if possible.

Verify mount status

After repair, check that SYS: partition is mounted read-write. In normal operation mode, attempt to create a test file in TNC:/ directory to confirm write access is restored.