235-0003

Document Control Configuration

Before any hardware intervention, save all machine parameters, PLC program, and tool tables to external USB media using the backup function in MOD > Data Transfer. Document the control's serial number and software version from the 'Version Info' screen.

Take photos of all DIP switch settings on the CC board and note the control's MC number (Main Computer) for proper board replacement ordering.

Perform Visual Board Inspection

Power down and lock out machine. Open control cabinet and locate the CC board (typically in the central slot of the NC backplane). Inspect for burnt components, bulging capacitors, or discoloration indicating thermal damage.

Ensure complete power isolation and discharge any capacitors by waiting 5 minutes after power-off before touching internal components.

Reseat CC Board

Remove CC board from backplane connector by releasing locking mechanism and carefully pulling straight out. Inspect edge connector contacts for corrosion or damage. Clean with isopropyl alcohol if necessary, then firmly reseat the board ensuring full insertion and locking.

Mark the original slot position with tape before removal. Some configurations require the CC board in a specific backplane slot.

Test After Reseating

Restore power and observe boot sequence. If alarm 235-0003 returns immediately or during self-test, the CC board has a permanent hardware failure and requires replacement.

If the control boots past the initial self-test but alarm appears during operation, this may indicate a thermal-sensitive component failure — verify cooling system operation first.

Arrange Board Replacement

Contact Heidenhain service with control serial number, MC number from board label, and software version. Order replacement CC board with exchange program if available. Upon installation, restore parameters from backup and verify system operation.

Heidenhain often requires the defective board return for exchange pricing. Keep original packaging from replacement board for return shipment.

Access Diagnostic Memory Test

If control boots partially, access MOD function. On iTNC 530/TNC 620/640, navigate to MOD > System > Diagnostics > Memory Test. Run the extended memory diagnostic routine and observe for reported errors.

On older TNC 320/530 controls without graphical MOD, power cycle and watch POST (Power On Self Test) messages during boot for memory error codes.

Identify Memory Module Location

Power down completely. Locate RAM modules on CC board — typically SIMM or SODIMM format modules in dedicated sockets. Check service documentation for your specific control model to identify memory module type and location.

Use proper ESD (electrostatic discharge) protection when handling memory modules. Wrist strap grounded to machine frame is mandatory.

Reseat or Replace Memory

Remove memory modules by releasing retention clips and pulling straight up. Inspect module contacts and socket pins for corrosion or damage. Clean contacts with electronics cleaner if needed. Reseat firmly until retention clips engage. If alarm persists, replace memory with Heidenhain-approved modules matching exact specifications.

Memory modules are control-version specific. Use only Heidenhain part numbers or approved equivalents. Generic computer RAM will not work and may cause permanent damage.

Verify Battery Backup

Check the lithium battery on the CC board (typically CR2032 or industrial equivalent). Low battery voltage can cause memory corruption and hardware errors. Measure battery voltage (should be >2.8V) and replace if below specification.

A weak battery may not trigger the dedicated low-battery alarm but can cause intermittent memory errors manifesting as alarm 235-0003.

Inspect Ribbon Cable Integrity

Power down control. Locate all ribbon cables connected to CC board (typically includes connections to display interface, keyboard/handwheel interface, and I/O boards). Inspect for physical damage, cracks in conductors, or stress at connector crimps.

Flex the ribbon cables gently near connectors while inspecting. Hairline cracks in the conductors will become visible as the copper traces separate.