Heidenhain 326419-59 LE426CB TNC 426 Main CNC Logic Unit
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Product Information
The Heidenhain 326419-59, designated as model LE426CB, is a CNC main logic unit developed for the TNC 426 series contouring controls. Serving as the primary processing unit in multi-axis metalworking machinery and precision milling centers, this controller governs up to five controlled feed axes along with spindle operation. Powered by a 24 V DC logic supply, the LE426CB executes complex axis path interpolation and machine PLC logic to ensure high accuracy in demanding machine tool environments.
Connecting the unit within a machine setup involves a selection of standardized communication and feedback ports, including a 100 Mbit/s Fast Ethernet RJ45 interface, an RS-232 / V.24 9-pin D-sub port, an RS-422 / V.11 25-pin D-sub port, and dedicated 15-pin HD D-sub inputs for 1 Vpp sinusoidal and EnDat absolute position encoders. Handwheel communication is supported via a 9-pin D-sub connection for HR 410 or HR 130 electronic handwheels. Standard replacement of this discontinued logic unit requires transferring machine parameters, PLC programs, tool tables, and NC files stored on the internal hard disk drive using TNCremo or TNCremoPlus software. When original configuration files cannot be accessed directly from a degraded unit, parameter extraction from the storage drive can be performed by ABC Industrial Parts before commissioning the spare module.
Diagnostic routines are supported through visual status LEDs on the front interface, including a 24V / Power indicator and a red ERR / Fault LED that signals hardware initialization or internal logic failures. Technicians can perform deeper troubleshooting using the integrated PLC diagnostic monitor, NC software oscilloscope functions, log file generation (LOGBOOK), and real-time I/O bit tracing via TNCremo software. Issues such as an emergency stop circuit trip or low buffer battery warning can be addressed by inspecting safety loop wiring or replacing the 3V lithium battery while powered up. Persistent board initialization errors or main memory self-test failures indicate internal hardware damage, where obtaining a tested exchange unit from ABC Industrial Parts provides an effective route to restore production capability.
Technical Specifications
| Manufacturer | Heidenhain |
| Part Number | 326419-59 |
| Model / Type | LE426CB |
| Product Family | TNC 426 |
| Component Type | CNC Main Logic Unit |
| Supply Voltage | 24 V DC |
| Controlled Axes | Up to 5 |
| Ethernet Interface | 100 Mbit/s (RJ45) |
| Serial Interface RS-232 / V.24 | 115200 bit/s (D-sub 9-pin) |
| Serial Interface RS-422 / V.11 | 115200 bit/s (D-sub 25-pin) |
| Encoder Inputs | 1 Vpp / EnDat (D-sub 15-pin HD) |
| Handwheel Interface | HR 410 / HR 130 Support (D-sub 9-pin) |
| Lifecycle Status | Discontinued |
Programming and Configuration
Configuration and execution of motion control routines on the LE426CB unit rely on machine parameters, PLC programs, NC program files, and tool tables stored within its internal hard disk drive. Non-volatile RAM storage is sustained by an internal 3V lithium buffer battery to retain critical parameters and system data when main 24 V DC power is removed.
Parameter transfer, system backups, and software updates are handled through the network or serial ports using TNCremo or TNCremoPlus communication utilities. Replacing a unit requires ensuring matching software release compatibility and alignment of installed expansion cards, after which system configuration backups can be restored directly to the replacement main logic board.
Communication and System Integration
The LE426CB provides multiple physical interfaces for network integration and peripheral connectivity. High-speed data transfer and network communication are handled through an integrated 100 Mbit/s Fast Ethernet port with an RJ45 connector. Serial communications are provided via an RS-232 / V.24 9-pin D-sub interface and an RS-422 / V.11 25-pin D-sub interface, both supporting transmission speeds up to 115200 bit/s.
Motion feedback signals connect through high-density 15-pin HD D-sub inputs designed for 1 Vpp sinusoidal position encoders and EnDat absolute encoders. For manual setup and positioning, the module includes a dedicated 9-pin D-sub handwheel interface compatible with HR 410 and HR 130 electronic handwheels.
Diagnostics and Status Indication
Hardware status is indicated directly on the module via front-panel LEDs. The 24V / Power LED monitors logic power supply status, while the red ERR / Fault LED alerts operators to hardware initialization problems or active system faults.
Advanced diagnostic and troubleshooting tools are accessible through the system software and communication tools. Available features include the integrated PLC diagnostic monitor, real-time status and I/O bit tracing, NC software oscilloscope functions, LOGBOOK event logging, and network-based diagnostic logging via TNCremo software.
Status LED Indicators
| LED | Color/Status | Meaning |
|---|---|---|
| 24V / Power | Solid / Off | Indicates 24 V DC logic power supply status. Off indicates loss of supply power or internal fuse blown. |
| ERR / Fault LED | Red - Solid / Flashing | System fault or hardware initialization failure. If illuminated persistently during startup, indicates internal hardware board failure requiring return for service. |
Replacement and Spare Part Considerations
When replacing an existing LE426CB logic unit, matching the exact part number 326419-59 ensures correct motherboard design, expansion card slot configuration, and encoder interface provisions. Software release compatibility must be verified prior to transferring system files to ensure seamless integration with existing drive modules and machine PLC settings.
Prior to removing a faulty logic unit, back up all machine parameters, tool tables, PLC programs, and NC files using TNCremo software. When installing a spare unit, power must be applied to perform parameter restoration. To avoid RAM data loss during maintenance, the 3V lithium buffer battery should be replaced while the system is powered on.
Error Codes & Fault Codes
The following error codes may be displayed during operation or diagnostics:
| Code | Name | Description | Possible Cause | Recommended Action |
|---|---|---|---|---|
| EMERGENCY STOP | Emergency Stop Triggered | The Emergency Stop control loop circuit was opened or internal safety circuit detected a fault. | Emergency Stop button pressed, machine enclosure open, or defective safety relay circuit. | Check safety circuit wiring, reset emergency stop button, confirm 24V supply to safety loop. |
| EXCHANGE BUFFER BATTERY | Buffer Battery Voltage Low | Lithium buffer battery voltage has dropped below critical threshold. | Buffer battery discharged or depleted due to age. | Replace 3V lithium battery while control is powered on to prevent volatile RAM memory loss. |
| POSITION ERROR | Contouring / Following Error Exceeded | The difference between actual position and target position exceeds defined machine parameter limit. | Mechanical overload, axis binding, drive controller fault, defective encoder signal. | Check mechanical axis freedom, verify drive controller status, test position encoder signal cable. |
| HARDWARE FAULT LE | Logic Unit Internal Hardware Failure | Internal processor, memory, or board self-test failed on startup. | Defective main logic board, internal memory failure, or damaged component. | Internal hardware failure — return unit to Heidenhain authorized service station for repair or replace LE 426 CB module. |
Frequently Asked Questions
How are machine parameters backed up before replacing the LE426CB controller?
Machine parameters, PLC programs, NC programs, and tool tables can be backed up over the Fast Ethernet port or serial connections using TNCremo or TNCremoPlus software.
What types of position encoders are supported by the LE426CB logic unit?
The LE426CB features 15-pin HD D-sub inputs supporting both 1 Vpp sinusoidal feedback signals and EnDat absolute encoders.
What should be done if the EXCHANGE BUFFER BATTERY fault message appears?
The 3V lithium buffer battery must be replaced while the control unit is powered on to prevent the loss of volatile RAM memory and critical machine data.
How can network communication be established with the LE426CB?
Network integration is supported via a 100 Mbit/s Fast Ethernet interface using a standard RJ45 connector, as well as RS-232 and RS-422 serial ports.
What does a persistent red ERR LED indicate during startup?
A persistent red ERR LED on startup indicates a system fault or internal hardware initialization failure on the main logic board, requiring unit service or replacement.
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Industrial plants prefer to keep running invariably, no matter what. Therefore, it is essential that you can rely on high-quality products and/or sustainable repairs. With our warranty conditions, you can count on certainty, whether you choose new, used or repaired products.
Data backup and recovery
Have you lost valuable parameters or data due to a malfunction while the manufacturer no longer provides support? At ABC Industrial Parts, we help you secure this data, both for common and specific products.
Specific firmware and hardware versions
If you are working with specific hardware or firmware versions that are no longer available from the manufacturer, ABC Industrial Parts is your partner. When making your enquiry, clearly state which versions you need, we will then look at the possibilities of supplying those versions, so that your installations continue to function optimally.
Disclaimer:
We are not an authorised distributor of Heidenhain.
Product photos are for illustration purposes only and may differ from the actual product delivered.
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