Don't Swap This Card Until You've Ruled Out the Terminal Board

An analog channel that's stuck at zero, pegged at full scale, or jumping around erratically is the number one reason an IS200VAICH1C gets pulled from a Mark VI VME rack — and in a large share of cases, the card is not actually at fault. Because field wiring never lands on the VAIC itself, start at the terminal board: a blown fuse, an open transducer loop, or a loose screw terminal on the TBAI (or DTAI) board reproduces the exact same symptom as a failed input channel on the card. Pull the terminal board cover, check for obvious wiring damage, and verify the transducer's own loop power before you condemn the VAIC.

What the VAIC Actually Does

The IS200VAICH1C is a VME Analog Input/Output card for the GE Speedtronic Mark VI turbine control system. It accepts 20 analog inputs and drives 4 analog outputs, using onboard signal conditioning, an analog multiplexer, an A/D converter, and a D/A converter to move real-world signals in and out of the controller. Two of the four output circuits are fixed at 4-20 mA; the other two can be configured for either 4-20 mA or 0-200 mA. Every input and output includes noise suppression circuitry against surge and high-frequency interference, and VAIC firmware adds configurable low-pass filtering on top of hardware filters already built into the terminal board.

A Feature Worth Knowing About: Compressor Stall Detection

VAIC firmware includes gas turbine compressor stall detection, evaluated at 200 Hz using the card's first four analog input channels. Depending on configuration, it runs one of two algorithms — a two-transducer version for small LM-type gas turbines, or a three-transducer version for heavy-duty gas turbines — tracking compressor discharge pressure (PS3) and its rate of change. If the algorithm detects a stall condition, VAIC sends a trip signal to the controller, which can be used to command the fuel shutoff valves. If you're chasing a nuisance stall trip, check the pressure transducers and their wiring first — the card is only as good as the signal feeding it.

Where It Sits: VME Rack, TBAI Terminal Board, VCMI

Field transducers wire into a TBAI terminal board mounted at the rear or side of the control cabinet. That terminal board links to the VAIC over a cable into the VME rack. The VAIC digitizes its inputs and passes them across the VME backplane to the VCMI communications card, which forwards the data to the controller. In a TMR configuration, one terminal board fans the same input out to three VAICs across the R, S, and T racks, and the three cards vote their outputs; a simplex configuration uses a single VAIC per terminal board.

Reading the Suffix: H1C and What It Means for Compatibility

IS200VAICH1C IS200VAICH1CBA falls into what the manufacturer treats as the "original" VAIC generation — everything up to and including H1C. This generation is rated for up to 500 Ω of load on a 20 mA output over 1,000 ft of #18 wire, and it requires a TBAIH1B-or-earlier terminal board, or any revision of DTAI. The later H1D generation raised that to 800 Ω and needs TBAIH1C or later, or an STAI terminal board — the two generations are not drop-in equivalents for each other's terminal boards. The letters after H1 (here, BA) track further revisions; match them against the label rather than assuming any H1C is identical. Our part number decoder walks through what each character in the full IS200 string represents.

Boards You'll Likely Also Need

TBAI, DTAI, and STAI terminal boards pair with VAIC depending on generation, and VCMI is the communications card that carries VAIC data to the Mark VI controller. Browse our full GE Mark VI IS200 boards collection if you're sourcing more than one card for the same outage.

Information to Send With Your RFQ

• Complete part number and suffix (IS200VAICH1CBA) plus a label photo if the revision is unclear
• Whether the panel is simplex or TMR
• Turbine model and site location
• How urgent the need is — unit down, planned outage, or spare stock

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