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Heidenhain Controller
Communication · Intermediate · 30-120 minutes
HEIDENHAIN 250-1393 - Error in internal communication
This alarm stems from disrupted data exchange between the TNC's central processing unit and its internal subsystems. The internal communication architecture relies on deterministic real-time protocols, and any degradation in signal integrity, timing synchronization, or hardware interface functionality triggers this safeguard alarm. Unlike external communication errors (Ethernet, device connections), this is an internal control integrity issue requiring hardware-level diagnosis.
250-1393
HEIDENHAIN 250-1393 - Error in internal communication
Error in internal communication
This TNC7/TNC 640 error indicates a communication failure with a connected device. Internal software error. The control cannot establish or maintain proper data exchange.
Root Cause Summary
This alarm stems from disrupted data exchange between the TNC's central processing unit and its internal subsystems. The internal communication architecture relies on deterministic real-time protocols, and any degradation in signal integrity, timing synchronization, or hardware interface functionality triggers this safeguard alarm. Unlike external communication errors (Ethernet, device connections), this is an internal control integrity issue requiring hardware-level diagnosis.
Safety
- Refer to Heidenhain service manual
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Power down and access control interior
Disconnect main power, wait 5 minutes for capacitors to discharge, and open the TNC control cabinet to access internal boards. Ground yourself to prevent ESD damage.
Ensure complete power disconnection and lockout/tagout before opening control cabinet. Residual voltage can persist on DC bus capacitors.
- 2
Inspect X116 and X126 internal connections
Locate the flat ribbon cable connectors X116 (PLC communication) and X126 (axis interface communication) on the CC board. Disconnect and reconnect each connector firmly, checking for bent pins, corrosion, or cable damage.
Take photos before disconnecting cables to ensure correct reassembly. Mark cable orientation with a marker if connectors lack keying.
- 3
Check SERCOS ring continuity
If your TNC uses SERCOS for internal axis communication, verify the fiber optic or electrical SERCOS ring connections between MC board and axis interface modules are secure and clean. Look for damaged fiber optic cables or dirty optical connectors.
SERCOS fiber connections are fragile. Never look directly into fiber ports and clean only with proper fiber cleaning tools.
- 4
Reassemble and test
Reconnect all internal cables, power up the control, and monitor for alarm recurrence. Check MOD > System Diagnostics > Communication Diagnostics to verify all internal bus channels show 'OK' status.
Use the TNCdiag function (MOD > Service > System Diagnosis > Create Diagnosis File) immediately after power-up to capture any transient communication errors during initialization.
Call a technician if:
- ·Software restoration required
- ·Internal hardware replacement needed
- ·Communication bus diagnosis required
- ·System timing issues persist
Prevention
- Regular system backup schedule
- Monitor memory usage trends
- Keep system software updated
- Perform periodic internal connection inspection
Common Mistakes
- Interrupting system file checks
- Changing multiple parameters simultaneously
- Ignoring PLC error logs
- Skipping proper ESD procedures during internal inspection
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Always verify with your machine manual or a certified technician before performing service procedures.