Code 230006: <location>Power unit: Thyristor Control Board
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Power unit: Thyristor Control Board 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
Message value: Drive object: All objects Reaction: OFF2 Acknowledge: IMMEDIATELY Cause: The Thyristor Control Board (TCB) of the Basic Line Module signals a fault. - there is no line supply voltage. - the line contactor is not closed. - the line supply voltage is too low. - line supply frequency out side the permissibl e range (45... 66 Hz). - there is a DC link short-circuit. - there is a DC link short-circui t (during the pre-charging phase). - voltage supply for the Thyristor Control Board ou tside the nominal range (5... 18 V) and line voltage >30 V. - there is an internal fault in the Thyristor Control Board. Remedy: The faults must be saved in the Thyristor Cont rol Board and must be acknowledged. To do this, the supply voltage of the Thyristor Control Board must be switched out for at least 10 s! - check the line supply voltage - check or energize the line contactor. - check the monitoring time and, if required, increase (p0857). - if required, observe additi onal power unit messages/signals. - check the DC link regarding short-circuit or ground fault. - evaluate diagnostic LEDs for the Thyristor Control Board.
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 230006 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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