126-011C

Power down and inspect HSCI cables

Turn off main power. Disconnect and inspect the HSCI cable at both the TNC control's HSCI port and the component at address %3. Check for bent pins, cable damage, and proper shield grounding to the connector housings.

Always disconnect main power before disconnecting HSCI cables to prevent damage to components.

Verify cable continuity and shielding

Use a multimeter to check continuity on all HSCI cable conductors. Verify shield continuity is less than 1 ohm to ground at both ends. Replace cable if any conductor shows open circuit or intermittent connection.

HSCI cables should never exceed 20 meters total bus length without repeaters. Excessive length can cause self-test timeouts.

Reconnect with proper torque

Reconnect HSCI cable connectors ensuring they seat fully with audible click. Tighten connector screws to 0.4-0.5 Nm torque specification. Ensure cable routing avoids sharp bends (minimum 10x cable diameter bend radius).

Power up and verify alarm clears

Restore main power and observe startup sequence. If alarm persists, check PLC program log in Test Mode to see if component now responds partially, indicating intermittent connection issue.

Measure supply voltage at component

With power on, measure 24VDC at the power input terminals of the component at HSCI address %3. Voltage must be between 22-28VDC under load. Check both voltage level and presence during control startup sequence.

Use proper measurement equipment rated for the voltage. Observe electrical safety protocols.

Check power supply loading and fuses

Verify the 24VDC power supply is not overloaded or in current-limiting mode. Check all fuses in the power distribution circuit to the HSCI component. Replace any blown fuses only after identifying overcurrent cause.

Inspect component power LED indicators

Observe the power LED on the HSCI component during startup. If LED does not illuminate or flickers, confirm power wiring polarity and secure terminal connections. Check for voltage drop in supply lines exceeding 1V.

Isolate power supply circuit

Temporarily disconnect other loads on the same 24VDC supply rail to eliminate power supply capacity issues. If alarm clears, calculate total current draw and upgrade power supply if necessary.

HSCI components typically draw peak current during self-test initialization. Ensure power supply has adequate capacitance and dynamic response.

Identify component from HSCI address

Access MOD > System Configuration > HSCI Configuration to correlate HSCI address %3 with the physical component type shown in %2. Document the component model number and firmware version if displayed.

Common HSCI components include PWM modules, I/O expansion cards, encoder interfaces, and PLCcontrol communication modules.

Perform component isolation test

Power down and temporarily remove the suspected component from the HSCI bus. If using daisy-chain topology, install jumper or bypass cable to maintain bus continuity. Power up to verify control startup without this component.

Check component firmware and LEDs

If component has diagnostic LEDs, observe the error pattern during startup (refer to component's documentation for LED codes). Check if firmware update is available through MOD > Service > System Update for the component type.

Never interrupt firmware updates once started. Ensure UPS or stable power during update process.

Swap with known-good component

If available, replace the suspected component with an identical known-good unit. Ensure HSCI address configuration matches either via DIP switches or software addressing. If alarm clears with replacement, original component is defective.

Contact Heidenhain Service

If component is confirmed defective, document alarm code, HSCI address, component model, and firmware version. Contact Heidenhain Service with this information for RMA procedure and replacement component ordering.