Where the TCQA Works Inside the Mark V

The DS200TCQAG2B is the main analog I/O board of the Speedtronic Mark V. One unit sits in position 2 of each of the <R>, <S>, and <T> cores — hence the "RST" in the family's commercial name. It receives and conditions the signals arriving at the terminal boards mounted on those same cores: LVDT inputs, servo-valve outputs, thermocouples, 4-20 mA inputs/outputs, vibration, relay outputs, pulses, and generator/line signals.

Specific Signals That Pass Through It

Worth noting: the 4-20 mA inputs associated with fuel flow pressure and compressor stall detection are scaled and conditioned specifically on the TCQA — not on another board in the core. If those values show up inconsistent on the HMI, the TCQA is a legitimate suspect, but not the only one.

mA Output Jumpers

The board carries jumpers J1/J2 (select the active mA output circuits), J5/J6 (set the mA output range between 20 mA and 200 mA), and J7/J8 (RS232 port for board testing and oscillator enable). When installing a replacement board, comparing these positions against the board being removed avoids reintroducing the same fault with a new board.

Diagnose Before You Buy

A real case discussed among Mark V engineers on the control.com forum illustrates the care required: a "TCQA LVDT POSITION DIFF HIGH" alarm generated hundreds of entries in a single day, and the cause wasn't the board — it was a field LVDT with an intermittent fault, a loose wire, or a moving core scraping the inside of the armature. The recommendation from whoever resolved the case was to use the AutoCalibrate screen to compare the feedback of the two LVDTs on the regulator involved before considering a TCQA swap. The same logic applies to any position-difference alarm: investigate the sensor and the field wiring before the board.

Use Voting to Your Advantage

Since the TCQA exists in triplicate (one per core), compare the value of the suspect channel across all three cores. If only one core disagrees with the other two, that core's board is the direct suspect. If all three cores agree on the same incorrect value, the problem tends to be in the sensor or the terminal board, not the TCQA.

Reading DS200TCQAG2B / DS200TCQAG2BDC

DS200TCQAG2B is the base reference; DS200TCQAG2BDC is the full revision stamped on the label. Always provide the complete code, with suffix, when requesting a quote.

This Unit

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

Details for Your Quote

• Full part number with revision suffix (photo of the label)
• Affected core (<R>, <S>, or <T>) and the revisions installed in the other two
• Mark V Simplex or TMR
• Whether you need a single board or a matched set
• Urgency

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

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