Stocking a Spare for a TMR Mark VI Panel

Most heavy-duty gas turbine Mark VI panels run Triple Modular Redundant (TMR) control, which means analog I/O is handled by three IS200VAICH1C cards at once — one in each of the R, S, and T VME racks — all reading the same terminal board and voting their outputs. If one card fails, the other two keep the loop alive at the correct value with no process bump, which is exactly why spares are usually kept on the shelf rather than bought after the fact. This listing is new surplus in factory packaging — the condition maintenance planners look for when building out a TMR spares kit rather than reacting to an unplanned failure.

What the Card Does Day to Day

The IS200VAICH1C is a VME Analog Input/Output board: 20 analog inputs and 4 analog outputs, with an analog multiplexer, A/D converter, D/A converter, and signal conditioning on board. It does not connect to field wiring directly — that lands on a TBAI terminal board, which links to the VAIC over a cable into the VME rack. The card converts field signals to digital values and sends them across the VME backplane to the VCMI communications card for delivery to the controller; for outputs, it reverses the process, converting a digital command back to an analog current at the terminal board.

Built-In Turbine Protection: Compressor Stall Detection

Beyond basic I/O, VAIC firmware runs gas turbine compressor stall detection at 200 Hz using its first four input channels, with separate algorithms for small LM-class and heavy-duty gas turbines based on compressor discharge pressure (PS3) and its rate of change. A detected stall condition trips a signal to the controller that can initiate fuel shutoff. It's a meaningful reason to keep this card's firmware revision matched to what your Toolbox configuration expects — not just any VAIC with the right connector will do.

If You're Replacing a Failed Card, Check This First

• A single bad channel is more often the terminal board or field transducer than the VAIC — verify wiring and loop power at the TBAI before condemning the card.
• In a TMR system, a channel flagged as deviating from the voted median usually points at that one field signal, not necessarily the card carrying the alarm.
• A hardware incompatibility fault after a board swap usually means the terminal board's ID chip (read automatically by the VAIC on startup) doesn't match what this VAIC generation expects — check terminal board compatibility, covered below, before assuming the new card is defective.
• Confirm rack power is fully removed before inserting or removing any VME board, and check that the RUN LED settles to flashing green after power-up.

Terminal Board Compatibility for This Generation

IS200VAICH1CCC belongs to the original VAIC generation (all versions through H1C). It requires a TBAIH1B-or-earlier terminal board, or any revision of DTAI, and is rated for up to 500 Ω of load on a 20 mA output over 1,000 ft of #18 wire. The later H1D generation needs TBAIH1C or later, or an STAI terminal board, and supports higher loop loads — the two families aren't interchangeable on the terminal board side, so don't mix generations without checking. For a full breakdown of what each segment of the part number means, see our Speedtronic part number decoder.

Also Stock These While You're At It

TBAI, DTAI, and STAI terminal boards, plus the VCMI communications card that carries VAIC data to the controller, are the parts most commonly ordered alongside a VAIC. See the full Mark VI IS200 boards collection for related cards from the same panel.

What We Need for a Quote

• Exact part number and suffix (IS200VAICH1CCC) and revision letters from the label
• Simplex or TMR configuration
• Turbine model and unit location
• Quantity and urgency

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