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Check NCU LED Status

Examine NCU front panel LEDs for hardware fault indicators. Red READY LED or flashing ERROR LED indicates NCU hardware problems.

Power down system before inspecting NCU board connections

Verify NCU Board Seating

Power down and reseat NCU board in rack. Check all connector pins for corrosion or damage, especially X101 and X102 connectors.

Use anti-static precautions when handling NCU boards

Test with Spare NCU

If available, swap NCU board with known good unit. If alarm clears, original NCU requires replacement.

Backup all machine data before NCU replacement

Contact Siemens Service

If NCU hardware failure confirmed, order replacement NCU and arrange for commissioning support.

Have NCU serial number and machine configuration ready for service call

Measure 24VDC Supply

Use oscilloscope to check 24VDC supply ripple at NCU X101 connector. Ripple should be <5% with stable voltage between 22.8-26.4VDC.

Check voltage under full machine load conditions

Verify UPS Battery Backup

Test UPS system functionality and battery condition. Weak batteries cause voltage drops during power transitions.

UPS failure can cause complete data loss during power outages

Check Grounding System

Verify electrical cabinet grounding and shield connections. Poor grounding causes electrical noise affecting memory operations.

Measure ground resistance - should be <1 ohm to earth ground

Install Power Line Filters

Add EMI filters to incoming power lines if electrical noise is detected. This prevents power-related memory corruption.

Use Siemens-approved power conditioning equipment

Clear SRAM Memory

Access Service menu → NCK → Memory → Clear SRAM. This removes corrupted data and reinitializes memory areas.

This operation deletes all machine data - ensure backup is available

Reload Machine Data

Restore machine data from backup archive via HMI → Commissioning → Data Backup → Restore. Load complete archive including parameters and programs.

Verify backup integrity before restoration process

Perform Memory Test

Execute extended memory test via Service → Diagnostics → Memory Test. Run complete test cycle to identify weak memory cells.

Memory test takes 30-45 minutes - schedule during maintenance window

Monitor for Recurrence

Log alarm occurrences and monitor system for repeated SRAM errors. Frequent recurrence indicates hardware replacement needed.

Document alarm frequency and conditions for trend analysis

Boot from Recovery Media

Insert Siemens recovery CF card and boot NCU in recovery mode. Access recovery menu via F8 during startup sequence.

Use original Siemens recovery media matching your NCK software version

Restore System Partition

Select System Recovery → Restore NCK Software. This reinstalls core NCK operating system and eliminates corrupted system files.

System restore deletes all user data and customizations

Reload Configuration Data

Import machine configuration via HMI → Commissioning → Machine Data. Load MD parameters, tool data, and work offset values.

Load machine data in sequence: basic MD first, then axis-specific parameters

Verify System Integrity

Run NCK diagnostic functions to verify proper system operation. Check all axes movement and spindle functions.

Perform complete machine checkout before returning to production

Identify EMI Sources

Survey facility for EMI sources near CNC control. Check for welding equipment, large motors, or radio transmitters within 50 meters.

Use EMI detector to measure field strength around NCU cabinet

Improve Cabinet Shielding

Verify electrical cabinet door seals and cable shield connections. Replace damaged EMI gaskets and ensure proper shield termination.

Maintain cabinet IP rating when modifying seals or connections

Install EMI Filters

Add ferrite cores to signal cables and install EMI filters on power inputs. Use Siemens-approved filtering components.

Install filters as close to NCU as possible for maximum effectiveness

Relocate EMI Sources

Move or shield EMI-generating equipment away from CNC control. Coordinate with facility management for equipment relocation.

Minimum 10-meter separation recommended for high-power EMI sources