IS220PTCCH1A: The Mark VIe Thermocouple Input Pack

The IS220PTCCH1A is a thermocouple (TC) input pack for GE's Mark VIe Speedtronic control system, offered here as a used unit at revision C, cleaned and tested. Its role is to read the millivolt-level signals produced by thermocouples around the turbine — exhaust, wheelspace, bearing, and process points — and convert them into temperature values the controller can act on. It is a distributed I/O pack: it clips onto a terminal board rather than sitting in a rack, and it reaches the controller over the IONet.

Inside, a common Mark VIe processor board is paired with an acquisition board built specifically for thermocouple measurement. One IS220PTCCH1A handles up to 12 thermocouple inputs; a second pack on the same terminal board can extend that to 24. Signals arrive through a thermocouple terminal board in the TBTC family across a 37-pin connector, power comes in on a three-pin connector, and two RJ45 ports carry IONet traffic. Reported inputs cover common thermocouple types — sources list E, J, K, and S (with T noted by some) — across a span on the order of -8 to +45 mV, digitized by a 16-bit converter with cold-junction compensation handled at the terminal board.

Cold-Junction, Sensor, or Pack? Diagnose Before Ordering

Thermocouple channels have one failure mode that RTD channels do not, and it fools people: the cold (reference) junction. Before you conclude that an IS220PTCCH1A has failed, work through the parts of the measurement that are far more likely to be at fault:

• The thermocouple itself. TCs degrade, drift, and open up in service. A channel reading full-scale or open is usually the sensor, not the pack.
• Cold-junction / reference issues. Because the terminal board provides cold-junction compensation, a temperature gradient across the terminal board, a loose sensor, or a compensation fault can bias every reading on that board. If all channels drift together, suspect the junction, not the pack.
• Extension wire and polarity. Thermocouple and extension wire must be the right type and correctly polarized; a reversed or mismatched run reads wrong in a characteristic way.
• Terminal board and connections. Inspect the TBTC terminations and the board itself before condemning the pack.
• Power and IONet. A pack missing from the controller is often a power-feed or network problem.

Use the pack's status LEDs and the ToolboxST diagnostics to confirm where the fault sits. A genuine pack failure is real, but it should be your conclusion after the sensor, wiring, junction, terminal board, power, and network are cleared — not before.

Making Sense of the IS220PTCCH1A Number and REV C

The part number divides into IS220 (Mark VIe distributed I/O pack), PTCC (the thermocouple input function), and H1A (group and revision). The separate revision marking — here REV C — identifies the specific hardware revision within that suffix. When you order a replacement, match both the suffix and the revision to your installed unit. Our GE Speedtronic Part Number Decoder explains each block.

Sister Packs and Terminal Boards

The thermocouple PTCC and the RTD PRTD are the two halves of Mark VIe temperature sensing; a site typically runs both. To understand where these packs came from, Mark V vs Mark VI: DS200 to IS200 traces the architecture change. Browse related hardware in GE Mark VI IS200 Boards and GE Speedtronic Turbine Control Boards.

What to Include in an RFQ

• The full part number with suffix (IS220PTCCH1A) and the revision — for this unit, REV C — on the label.
• A photo of the label if you can.
• Turbine model and Mark VIe generation.
• Quantity and urgency.

Request Your IS220PTCCH1A Quote

This IS220PTCCH1A (REV C) is a used unit, cleaned and tested, and backed by the warranty stated below. Click Request a Quote and we will respond within 24 hours, ship worldwide on DDP terms, and accept purchase orders.