The Board Behind Every Servo-Valve Regulator

Every servo-actuated control valve on the turbine train — fuel valve, speed ratio, IGV — has its regulator implemented in the firmware of the DS200TCQAG1B. In a TMR system, each of the servo's three coils connects to a different core (<R>, <S>, and <T>), and the TCQA on each core supplies the current (typically a fraction of a mA) that holds the actuator at the reference position. Understanding this relationship helps explain why a suspect TCQA almost always shows up tied to a specific regulator number (SVO), rather than to the board as a whole.

Where It Lives and What It Conditions

The TCQA occupies position 2 of each of the Mark V's <R>, <S>, and <T> cores. Besides the servo-valve regulators, it conditions LVDT, thermocouple, 4-20 mA, vibration, pulse, and generator/line signals bound for the terminal boards on the same core.

Diagnose Before You Buy

If the servo current shows up unstable or unbalanced across the three cores, that alone doesn't prove a TCQA fault. Before requesting a replacement:

• Compare the reference and the actual position (feedback from the two LVDTs) on the AutoCalibrate screen across all three cores — if the reference is the same across all three but only one core shows unstable current, suspicion falls on that specific core.
• Check the null-bias current configured in the I/O Configurator — a value mismatched to the physical valve generates oscillation that looks like a board fault.
• Inspect the LVDT itself and its field wiring — a misaligned moving core or a loose wire is a more common cause of position mismatch than the conditioning board.
• Only after ruling out the sensor, wiring, and configuration is it worth physically replacing the TCQA.

Reading the Part Number

DS200TCQAG1B is the base (DS200 family, TCQA function, G1 group, B revision); DS200TCQAG1BED is the full revision on the physical label. Always use the complete code when requesting a quote.

This Unit

Used, cleaned and tested, with a 1-year warranty.

Details for Your Quote

• Full part number with suffix (photo of the label)
• Affected core and which regulator/SVO is involved, if known
• Revisions installed in the other two cores
• Mark V Simplex or TMR, and urgency

Request a quote through Request a Quote: response within 24 hours, worldwide DDP dispatch, purchase orders accepted.

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