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Access System Log Files

Press MOD key, navigate to System > LOG FILES, and examine the *.log files for detailed assertion information. Note the timestamp, module name, and assertion condition that failed.

The log file typically contains the exact source code location (file and line number) of the failed assertion, which is critical information for Heidenhain support analysis.

Verify Software Version Integrity

In MOD mode, select System Information and verify the software version matches expected installation. Check for partial or incomplete software updates indicated by mismatched build numbers.

Do not attempt software operations while machine axes are enabled or workpieces are mounted.

Backup Current Configuration

Using TNCbackup or MOD > Backup > Create Backup, save current machine parameters and PLC program to external media before any software reinstallation attempts.

Perform Clean Software Installation

Boot control with installation media (USB/CF card), select 'New Installation' option, and reload the complete TNC software package. Restore machine parameters after successful installation.

Use the latest service pack version available for your control model, as many assertion-related bugs are fixed in newer releases.

Boot into SERVICE Mode Diagnostics

Power off the control, then power on while holding the CE key. From the SERVICE menu, select 'Memory Test' to perform comprehensive RAM diagnostics. Allow the full test cycle to complete.

SERVICE mode operations may take 15-30 minutes. Do not interrupt power during diagnostic procedures.

Examine Hardware Status Indicators

In SERVICE mode, check System > Hardware Status for component health indicators. Look for memory module errors, storage device warnings, or board communication failures.

Test with Minimal Configuration

Disconnect all optional hardware (encoder interfaces, additional I/O modules, network connections except essential items) and restart. If alarm clears, reconnect modules individually to isolate faulty hardware.

Replace Defective Memory Components

If memory test failures are confirmed, replace the CC (Control Computer) board or affected memory modules. Use only Heidenhain-approved replacement parts with matching firmware versions.

Before board replacement, photograph all DIP switch positions and cable connections on the existing board for exact replication.

Boot Without PLC Program Execution

Access SERVICE mode and select 'Start without PLC' option. If the control boots successfully without the assertion alarm, the PLC program is likely the root cause.

On iTNC 530/TNC 620/640 controls, you can disable PLC execution via MOD > PLC > Settings by unchecking 'Automatic Start'.

Review Recent PLC Modifications

In PLC > Edit mode, examine any recently modified PLC modules. Look for memory marker conflicts, timer overflows, or use of undocumented system markers that may conflict with control internals.

Validate PLC Compile Results

Recompile the PLC program using PLC > Compile All. Review the compile log for warnings about memory usage, marker conflicts, or deprecated function usage that could cause runtime issues.

Test with Default PLC Program

Temporarily load a minimal default PLC program (machine manufacturer's original version) and restart the control. If alarm does not recur, systematically reintroduce PLC modules to identify the problematic code section.

Replacing PLC programs affects machine safety logic. Ensure emergency stop and safety door functions are tested before normal operation.

Inspect Internal Cable Connections

Power down control and inspect all ribbon cables and connectors between CC, MC, and PL boards. Reseat all connections firmly, checking for bent pins, corrosion, or physical damage.

Observe proper ESD precautions. Disconnect main power and wait 5 minutes for capacitor discharge before handling internal components.