When the Alarm Points to the TCQA and the Problem Is Somewhere Else

A case documented on a technical forum for GE Mark V engineers illustrates a common trap well: a plant with two Frame 9E TMR units was seeing out-of-spec voltages on the DIAGC DATA screen, attributed to the TCQA on one of the cores. The team swapped, in this order, the TCPS, the TCQA, and the TCQC on the suspect core — with no result. Only when two other boards (SDCC/SLCC) were swapped between cores did the symptom "follow" the hardware, revealing that the likely cause wasn't any physical board at all, but a DIAGC.DAT calibration file that was out of date relative to the boards and PROMs actually installed. The takeaway for anyone maintaining a Mark V: an "out of limit" voltage reading on the diagnostic screen is not proof of a burned-out board.

What This Board Does

The TCQA is the Mark V's main analog I/O board, mounted in position 2 of each of the <R>, <S>, and <T> cores. It scales and conditions the LVDT, servo-valve, thermocouple, 4-20 mA, vibration, pulse, and generator/line signals arriving at the core's terminal boards.

Before Buying a TCQA Over a Voltage Alarm

• Check all the TCPS fuses (the power supply board, usually in position 5 of the core) before suspecting the TCQA.
• Note the board and PROM revisions actually installed and compare them against what the system's DIAGC.DAT expects — mismatches here generate misleading readings without any board being physically at fault.
• If boards were recently swapped (including SDCC/SLCC) without updating the corresponding calibration file, that's a more likely cause than a second burned-out board.
• Only after ruling out these possibilities is it worth physically replacing the TCQA.

Reading the Part Number

DS200TCQAG1A is the base reference; DS200TCQAG1AEC is the full revision stamped on the board's label. Provide the complete code, with suffix, when requesting a quote.

This Unit

New surplus in original factory packaging, with a 1-year warranty — useful when you need a shelf part with no operating history.

Details for Your Quote

• Full part number with suffix (a photo of the label helps confirm the revision)
• Destination core and the revisions installed in the other two cores
• Mark V Simplex or TMR
• Whether it's an emergency replacement or a stock part

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

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