231-C031

Check HSCI Bus Diagnosis

Access MOD function, select 'Service' menu, then 'HSCI Bus Diagnosis' to identify which specific HSCI component reported the voltage fault.

The diagnosis will show exact device address and voltage readings for each HSCI component

Measure 24VDC Supply Voltage

Use multimeter to measure 24VDC supply at X116 connector (pins 1-2) on NC unit and at affected HSCI device power input terminals.

Ensure proper lockout/tagout procedures before accessing electrical connections

Check Power Supply Loading

Verify total current draw of all HSCI components against power supply capacity. Check machine parameter MP7680 for configured HSCI device count.

Each PL module typically draws 2-3A, MB panel draws 1-2A, calculate total load accordingly

Inspect Power Supply Unit

Check 24VDC power supply unit for proper operation, cooling, and output voltage regulation under load conditions.

Identify Affected PL Module

In HSCI Bus Diagnosis, locate PL module showing voltage fault. Note the PL address from machine parameter MP1020 (PL configuration).

PL modules are typically addressed as PL0, PL1, etc. in the HSCI diagnosis display

Disconnect PL I/O Connections

Power down system and disconnect all I/O field wiring from the suspected PL module to isolate potential short circuits in connected devices.

Document all wire connections before disconnecting for proper reassembly

Test PL Module Isolation

Power up system with PL I/O disconnected. If C031 clears, the fault is in external I/O wiring. If alarm persists, PL module internal fault is confirmed.

Check machine parameter MP1021 for PL module type and specifications

Reconnect I/O Systematically

If external wiring fault suspected, reconnect I/O devices one at a time while monitoring HSCI voltage levels to isolate faulty circuit.

Check MB Panel in HSCI Diagnosis

Verify MB panel appears in HSCI Bus Diagnosis and note any voltage readings. Check machine parameter MP7300 for MB panel configuration.

MB panel should show stable 24VDC ±5% in HSCI diagnosis when functioning properly

Inspect MB Panel Connections

Check X401 connector on MB panel for loose connections, corrosion, or damaged pins affecting power supply to the panel.

Handle MB panel connectors carefully as they contain sensitive communication circuits

Test MB Panel Power Input

Measure 24VDC at MB panel power input while monitoring for voltage fluctuations during panel operation and key presses.

Evaluate Panel Internal Circuits

If input voltage is stable but C031 persists, MB panel internal power regulation circuits may be faulty requiring panel replacement.

Inspect HSCI Cable Connections

Visually inspect all HSCI bus cables (typically X401 series connectors) for physical damage, bent pins, or loose connections between NC unit and HSCI devices.

HSCI cables carry both communication and power, damaged cables can cause both communication and voltage issues

Check Cable Continuity

With system powered down, use multimeter to verify continuity of power conductors in HSCI cables, particularly pins 1-2 (24VDC) and pins 3-4 (0VDC).

Ensure system is completely powered down before checking cable continuity

Test Communication Integrity

Access machine parameter MP7681 to check HSCI communication error counters and verify stable communication with all configured devices.

Replace Suspect Cables

Replace any HSCI cables showing continuity issues or physical damage, ensuring proper connector orientation and secure connections.

Verify MC Status in Diagnostics

Check HSCI Bus Diagnosis to confirm MC main computer is reporting the voltage fault. Review machine parameter MP7000 for MC configuration details.

MC internal faults often accompany other system instabilities or communication errors

Check MC Power Input

Measure incoming power to MC unit at main power connector, verify all supply voltages (24VDC, ±15VDC if applicable) are within specification.

MC main computer contains sensitive electronics, avoid static discharge during inspection

Monitor MC Internal Voltages

If available, use TNC internal voltage monitoring functions to check MC internal power rail voltages and identify specific failing circuits.

Plan MC Replacement

MC internal power faults typically require main computer replacement. Contact Heidenhain service for MC unit replacement and system reconfiguration.

Document all machine parameters before MC replacement as reconfiguration will be required