The GE Fanuc IC660BBA025K is a Discrete Input/Output Terminal Board designed for GE Mark VIe turbine control systems. It provides a field wiring interface for discrete contact signals and relay outputs, while also supporting a triple modular redundancy (TMR) architecture for applications where control availability and fault tolerance are important.

Product Overview

This terminal board is commonly identified as the TDBT type within the Mark VIe platform. Its primary role is to receive discrete signals from field devices and route them to the appropriate PDIO I/O packs. In addition, relay outputs provide an interface for control signals going to external devices.

The board supports 24 group-isolated contact inputs. These inputs can use externally supplied wetting voltages of 24, 48, or 125 VDC. Furthermore, input conditioning and noise suppression help protect the control system from electrical disturbances, surges, and high-frequency interference.

Main Technical Features

The input circuits are designed for industrial contact monitoring. According to available technical descriptions, channels 1–21 limit input current to approximately 2.5 mA, while channels 22–24 can operate at approximately 10 mA. Therefore, the board can accommodate different field-contact requirements while maintaining controlled input characteristics.

TMR Signal Architecture

One of the important characteristics of this terminal board is its application in redundant Mark VIe control systems. Three PDIO I/O packs can interface with the board through dedicated D-type connections. This arrangement allows the field signals to participate in a TMR control architecture.

Moreover, redundant signal paths can improve system availability because the control system can continue operating even when one part of the control path experiences a fault. In turbine control and protection applications, this redundancy is particularly valuable because unexpected signal or hardware failures can have a significant operational impact.

The TDBT architecture is therefore more than a simple terminal interface. It forms part of the signal distribution layer between field devices, I/O processing hardware, and the redundant controller network.

Relay Output Capability

In addition to its contact-input section, the board provides 12 Form-C relay outputs. These outputs can be used for switching or control functions associated with industrial equipment.

For applications requiring additional relay functionality, an optional relay expansion card can be installed through the designated board connectors. As a result, the terminal assembly can be adapted to different control and protection requirements without completely redesigning the field interface.

Typical output-related applications include interlocks, auxiliary control circuits, alarm functions, and equipment status control. However, the exact field wiring should always follow the applicable Mark VIe system documentation and project wiring drawings.

Hardware and Installation

The board is intended for installation inside an industrial control cabinet. It can be mounted on a DIN rail or attached to a flat panel, depending on the cabinet configuration.

The field wiring section provides dedicated terminal connections for the input and relay circuits. Meanwhile, the rear or board-mounted connectors provide the interface to the associated I/O packs. This separation makes cabinet wiring easier to organize and can simplify troubleshooting during commissioning or maintenance.

The PCB is also available with conformal coating, which helps provide additional protection against moisture, dust, and other environmental contaminants. Therefore, it is suitable for demanding industrial control environments when installed within the recommended system enclosure.

Typical Applications

This terminal board is primarily associated with GE Mark VIe turbine control applications. Typical uses include:

• Gas turbine control systems
• Steam turbine control systems
• Generator control and protection
• Power generation plants
• Oil and gas facilities
• Industrial turbine auxiliary systems
• Discrete field-device monitoring
• Emergency and equipment interlock circuits

For these applications, the board provides a practical connection point between field contacts and the Mark VIe control architecture. Furthermore, its redundant I/O capability makes it appropriate for systems where availability and dependable signal processing are important.

Replacement and Maintenance Notes

When replacing an existing unit, technicians should verify the complete part number, hardware revision, system configuration, terminal wiring, and associated PDIO I/O pack arrangement before installation. Similar-looking terminal boards may have different electrical configurations or connection assignments.

Before maintenance, isolate the relevant power and field circuits according to site procedures. Check terminal connections for looseness, corrosion, or damaged insulation. In addition, inspect connectors and wiring for signs of overheating or mechanical stress.

Because this board can form part of a redundant turbine control system, replacement should also be followed by appropriate signal verification and system diagnostics. Consequently, checking each field input and relay output after installation is recommended before returning the control system to normal operation.

Why Choose This Terminal Board?

The main value of this GE terminal board is its combination of high-density field interfacing, discrete signal conditioning, relay output capability, and TMR compatibility. It provides a structured connection between field devices and the Mark VIe I/O architecture while helping maintain reliable signal transmission.

For maintenance teams supporting existing Mark VIe installations, selecting a correctly matched replacement is especially important. With the proper wiring and I/O configuration, this terminal board can help extend the service life of established turbine control systems and reduce unnecessary changes to the existing cabinet infrastructure.