Code 231-8A50: Inverter not ready %1
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Inverter not ready %1 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] - Power-on of the drive not possible, because an inverter is not ready (RDY signal). - No pulse release, 24 V is missing on the terminal X71 or X72 - On interface PCBs for Siemens inverters, the second axis is not enabled - Compact inverter, inverter supply unit or power module is defective - Interruption at inverter bus cable (supply bus, unit bus, PWM bus) - Defective PWM interface on the control [Error correction] - Correct the defect in the pulse inhibitor on power supply module UV, X71/72 - Replace the defective compact inverter, supply unit or power module - Replace the defective cable - Inform your service agency
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 231-8A50 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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