126-011B

Identify the affected component

Read the alarm parameters %2 (component type such as inverter, UVR, or UM) and %3 (HSCI address number). Document these for reference during troubleshooting.

Common HSCI addresses: Inverter modules typically 1-3, UVR (voltage monitoring) at 4, UM (power measurement) at specific addresses depending on machine configuration.

Inspect HSCI cable connections

Power down the control completely. Check the HSCI cable connection at the CC board (or UEC board on newer controls) inside the TNC cabinet and at the receiving component. Ensure connector locking clips are fully engaged and there is no visible cable damage.

Ensure main power is isolated and lockout/tagout procedures are followed before opening cabinet doors.

Check cable shield continuity

Verify that the HSCI cable shield is properly grounded at both ends. Use a multimeter to check shield continuity. Heidenhain HSCI cables must maintain shield integrity for proper signal transmission.

HSCI cables are sensitive to EMI. Keep them separated from power cables and ensure they are routed through proper cable management channels.

Replace HSCI cable

If any doubt exists about cable integrity, replace with a genuine Heidenhain HSCI cable of the correct length. After replacement, power up and observe if the alarm clears during initialization.

Never use longer HSCI cables than necessary. Excessive length or non-Heidenhain cables can cause communication timing issues.

Access HSCI diagnostic information

Enter Service Mode by holding MOD key during power-up, then navigate to System Information → HSCI Components. Check if any devices are being detected at all on the bus.

If no HSCI devices are visible but they were previously, this points to the CC/UEC board rather than individual components.

Check CC/UEC board LED indicators

Locate the CC or UEC board in the control cabinet. Observe the HSCI status LEDs during power-up. Normal operation shows brief activity then steady state. Continuously flashing or no activity indicates board-level failure.

Work with control powered to observe LEDs, but do not touch any circuitry. Maintain safe distance from high-voltage areas.

Verify board seating and connections

Power down completely. Reseat the CC/UEC board in its backplane connector. Ensure all connectors to the board are properly secured, including the HSCI output connector(s).

Use proper ESD precautions when handling control boards. Wear grounding strap and avoid touching component leads.

Test with known-good board

If available, swap the CC/UEC board with a known-good spare or from a functioning identical control. If alarm clears, the original board is defective and requires replacement through Heidenhain service.

CC/UEC boards are control-specific and may require configuration transfer. Document all settings before board replacement.

Identify the specific component type

Use the %2 parameter from the alarm to determine component type and %3 for HSCI address. Cross-reference with machine documentation or Service Mode → System Configuration to identify the physical component location in the cabinet.

On multi-axis machines, HSCI address typically corresponds to axis assignment: Address 1 may be X-axis inverter, 2 is Y-axis, etc.

Check component power supply

Verify that the component at the affected HSCI address has proper DC bus voltage and control voltage. Check the component's power LED indicators and measure voltages at test points per the component's service manual.

High DC bus voltages (300-600V DC) are present. Use appropriate voltage-rated test equipment and PPE.