The GE IS200TDBTH2A (commonly designated as the TDBT board) is a Group Isolated Discrete Contact Input Terminal Board manufactured by General Electric for Speedtronic™ Mark VI and Mark VIe turbine control systems. Installed in control cabinets, it accepts 24 discrete field contact inputs (e.g., limit switches, pushbuttons, and auxiliary contacts) and provides optical/group isolation to protect control electronics before routing signals to processing modules or I/O packs.
Key Specifications & Identification
| Attribute | Details |
| Manufacturer | General Electric (GE / GE Vernova) |
| Part / Revision Code | IS200TDBTH2A (TDBT Board Family) |
| System Compatibility | GE Speedtronic™ Mark VI & Mark VIe Control Systems |
| Input Channels | 24 Discrete Contact Inputs (Group Isolated) |
| Terminal Blocks | 2 × Large Barrier/Screw Terminal Blocks (48 total screw terminals) |
| Compatible I/O Packs | IS220PDIOH1A (Mark VIe Discrete I/O Pack) |
| Redundancy Modes | Supports Simplex, Dual, and Triple Modular Redundancy (TMR) |
| Certifications | Approved for Class I, Division 2 / Hazardous Location (HazLoc) operation |
Primary System Functions
- Discrete Signal Termination & Isolation: Serves as the landing interface for up to 24 field contact input wires. Onboard group isolation circuitry prevents ground loops and electrical line noise from penetrating internal logic buses.
- TMR Distribution & Cabling: Features 3 D-sub cable connectors (
D-sub 37-pin) to fan out field contact signals simultaneously across<R>,<S>, and<T>processor channels for 2-out-of-3 (2oo3) voting architectures. - Direct Mount for Mark VIe I/O Packs: In Mark VIe distributed control architectures, IS220PDIOH1A discrete I/O packs mount directly onto the board’s connector headers.
- Transient & Noise Suppression: Integrates RC filter networks and voltage surge suppression devices (MOVs/TVS) to cushion field inputs against switching transients and high-voltage surges.
Servicing & Installation Guidelines
- Field Voltage Verification: Discrete input contacts can carry external DC or AC field excitation voltages. Always verify zero potential across all terminal points with a calibrated multimeter before landing or removing field wires.
- ESD & Static Precautions: Sensitive onboard isolation optocouplers and connector pins require anti-static handling. Always wear a grounded ESD wrist strap when working on or replacing the board.
- Cable Fastening & Strain Relief: Ensure D-sub interface cables or IS220PDIO I/O packs are securely screwed into place to prevent pin detachment caused by cabinet vibration.
- Terminal Screw Torque: Fasten field connections using the recommended screw torque settings specified in GE manual GEH-6721 / GEH-6725 to maintain low-resistance contact points.
