Code 235-0078: HSCI cabling error: Too many devices on X501
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical HSCI cabling error: Too many devices on X501 alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
[Cause of error] There are too many HSCI components connected to X501 of the MC [Error correction] - Check the HSCI cabling. - Use the default values of your control's Technical Manual for the maximum number of HSCI components. - Check the HSCI configuration. It may be possible to connect HSCI components to the X500 connector of the MC. - Generate the service files and inform your service agency. 10/2023 [597]
Source: HEIDENHAIN NC Error Messages — TNC7/640/620/320/128, CNC PILOT 640, MANUALplus 620 (10/2023)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Heidenhain TNC Series CNC Alarms
Heidenhain controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 235-0078 on the TNC Series CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Heidenhain's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4497 Heidenhain TNC Series CNC codes.
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