What the IS200TTURH1BBA Does for Generator Synchronizing

The IS200TTURH1BBA is the Turbine Termination terminal board GE built into the Mark VI Speedtronic system specifically to handle turbine speed sensing and generator synchronizing. It monitors the generator and line (bus) voltages through potential transformer inputs, matches turbine speed to line frequency, and once conditions line up, energizes the generator breaker coil (52G) at a nominal 125 V DC to close the breaker. Three relays do the gatekeeping on that last step — K25 (auto synch), K25P (synch permissive), and K25A (an internal synch check relay) — all of which have to be satisfied before 52G gets power. An external synch check relay is wired in series with K25/K25P through the TTUR as an added layer of protection, and feedback from the breaker's own 52G/a auxiliary contact (not a relay copy) confirms the actual closing time back to the control system.

This board is a terminal board, meaning it's where the field wiring lands — magnetic speed pickups, shaft voltage/current sensors, and PT wiring connect to two 24-terminal blocks (TB1 and TB2, rated for wire up to #12 AWG), with jumpers JP1/JP2 selecting simplex or TMR relay-drive mode. The actual control logic runs on a separate VME card, VTUR, inside the R/S/T Control Module, tied to the TTUR by cable through six connectors: JR1/JR5, JS1/JS5, and JT1/JT5.

Before You Blame the Board

Synchronizing problems and speed alarms have several possible causes upstream of the TTUR itself:

• If the unit won't synchronize or the breaker won't close, check the external synch check relay, the 52G/a feedback contact from the breaker, the PT wiring and fuses, and the JP1/JP2 jumper settings before assuming the board has failed.
• If speed readings are erratic or an overspeed trip looks suspicious, check the magnetic pickup's air gap and the wiring between the pickup and TB1/TB2 first — that's a far more common cause than a bad terminal board, and in TMR systems it typically shows up as a voting disagreement between channels rather than an outright fault.
• If you're seeing a shaft voltage or shaft current alarm, that's usually a grounding brush or bearing insulation issue on the physical shaft train — the TTUR and VTUR only monitor for that condition, they don't cause it.
• Check for loose terminals on TB1/TB2 and properly seated JR/JS/JT connectors before ordering a replacement board.

Understanding the IS200TTURH1BBA Suffix

IS200 is the platform prefix, TTUR the function code, and H1BBA the group and revision — H1B for the group/generation, BA for this specific revision. Match the complete part number when sourcing a replacement; the H1B and H1C groups both stocked in this collection share the TTUR function but are separate hardware generations. Our GE Speedtronic Part Number Decoder explains how to read the full string.

Related Boards

The TTUR's companion VME card is VTUR, mounted in the Control Module. The generator breaker trip circuit also runs through the TRPG terminal board (driven by VTUR) and the TREG terminal board in the Backup Protection Module (driven by the VPRO card). For older equipment, see our Mark V vs Mark VI: DS200 to IS200 guide and GE Mark V DS200 Boards Explained article. Browse the rest of the family in our GE Mark VI IS200 Boards collection or the wider GE Speedtronic Turbine Control Boards collection.

What to Include in Your Quote Request

• Full part number with suffix: IS200TTURH1BBA
• Revision from the label
• Photo of the ID label
• Turbine/generator model and unit ID
• Planned outage or urgent need
• Quantity

Request a Quote

This IS200TTURH1BBA is listed in used condition, clean and tested, with a 1-year warranty (see table below). We quote every order directly rather than posting prices online — submit a Request a Quote and expect a reply within 24 hours. We ship worldwide DDP, accept purchase orders, and support both planned outages and urgent breakdown needs.

General Information about the Product
Part Number	IS200TTURH1B Mark VI IS200
Description	GE General Electric IS200TTURH1B IS200TTURH1BBA Terimination PC Board Mark VI
Condition	used Clean and Tested. With 1 Year Warranty