6640

Power down the 840D control completely and wait 30 seconds for capacitive discharge.

Ensure emergency stop is activated before powering down.

Visually inspect the card reader slot on the front panel for obstruction, debris, or damage. Insert the NC card firmly into the slot until it clicks and is flush with the front panel.

Do not force the card; proper insertion should require moderate pressure only. Forcing may damage card contacts or reader pins.

Power up the 840D and observe the boot sequence. Check the Diagnosis menu path: Machine → Diagnosis → Card → Card Status to confirm card detection.

If alarm 6640 persists, test with a known-good NC card to rule out card reader hardware failure.

Remove the NC card by pressing the eject button or gently pulling the card straight outward. Inspect both the card edge contacts and reader slot pins for corrosion, oxidation, or mechanical damage.

Handle the card by edges only; avoid touching gold contact surfaces.

Clean the card edge contacts with a soft, dry, lint-free cloth. If oxidation is present, use isopropyl alcohol (≥90%) on a cotton swab, allow to air-dry completely (minimum 2 minutes), then reinsert.

Never use abrasive materials or water-based cleaners; allow complete drying before reinsertion to prevent short circuits.

Reinsert the card straight into the slot with firm, even pressure. The card should seat completely flush; listen for an audible click from the retention mechanism.

Cycle power to the control and verify card detection via Diagnosis → Card → Card Status. If intermittent detection occurs, schedule replacement of the card reader module.

Test with a second known-good NC card from another 840D system. If alarm 6640 persists with multiple cards, the reader hardware is likely faulty.

Access the Service menu (requires technician level access) and navigate to: Maintenance → Hardware Diagnostics → I/O Modules → Card Reader. Record any specific error codes or communication status messages.

This menu requires password-protected access; contact your local Siemens service organization if access is restricted.

Visually inspect the ribbon cable connection between the front panel card reader and mainboard. Power down, unseat and reseat the ribbon cable connector firmly, then power up and retest.

Do not apply excessive force to ribbon connectors; use firm, steady pressure only.

If alarm 6640 persists after testing with multiple cards and reseating cables, schedule replacement of the card reader module or mainboard with Siemens Field Service. Document the serial number (MD 19000) and firmware version for the service call.