IS220PDIAH1A REV. C I/O Pack: Function and Fit

PDIA is GE's Speedtronic Mark VIe pack for discrete contact inputs — it sits between the field contacts (limit switches, pressure switches, valve position indicators, trip signals, pushbuttons) and the <R>, <S>, or <T> controller, reading up to 24 contact inputs and passing them digitally over the I/O Ethernet network (IONet) through dual RJ-45 ports. The pack mounts directly on a discrete input terminal board via a single DC-37 pin connector; it does not process anything on its own without that board attached.

Each of the 24 inputs runs through its own comparator with a variable threshold, is opto-isolated from the control logic via an isolated power supply, and includes filtering, hysteresis, and a dedicated yellow status LED. The pack supports three different input voltage levels depending on the terminal board fitted (TBCIH1, H2, or H3), plus a path for the isolated, voltage-sensing TICI board; compatible terminal boards are TBCI, TICI, and STCI (not the DIN-rail DTCI board). Optical isolation is rated to 1500 V, with a 4 ms hardware filter and an operating range of -40 to +70°C. GE documents this pack in the GEH-6721 Mark VIe Control System Guide.

Diagnostic Steps Before You Replace This Pack

• First, establish your I/O configuration — Simplex, Dual, or TMR — since that changes how a fault should behave and what "normal" looks like.
• Separate Process Alarms (a bad field reading) from Diagnostic Alarms (a hardware or communications fault, such as a watchdog fault) — they have different root causes.
• If the pack is at a remote location feeding back to the main panel over its own switch and possibly fiber, treat that entire path — not just the pack — as a candidate for the fault.
• Check whether your IONet switches are a current hardware revision; GE has issued Technical Information Letters (TILs) specifically about switch reliability issues that can present as pack-level symptoms.
• Confirm cable bend radius is within spec, and inspect connectors for corrosion or discoloration — small physical issues at the cable end can cause intermittent, hard-to-reproduce faults.
• The decisive test: swap the pack to a different terminal board (or install a known-good pack on the suspect board) and watch whether the fault follows the pack or stays with the board. Field reports on this exact pack type confirm this test is the fastest way to avoid replacing the wrong part.

What REV. C Means Here

IS220 marks a Mark VIe distributed I/O pack, PDIA the contact input function, H1 the design generation, A the hardware revision, and REV. C the board revision within this part number. Confirm the complete string against your terminal board and ControlST project before ordering. Our GE Speedtronic Part Number Decoder explains GE's full naming logic.

Related Packs and Boards

PDIA pairs with TBCI/TICI/STCI-family terminal boards. For discrete outputs, see the related PDOA pack, or PDIO where a single pack handles both input and output on a combined terminal board. Our GE Speedtronic Turbine Control Boards collection covers the wider Mark V/VI/VIe range.

What We Need to Quote This

• Full part number with suffix and revision (IS220PDIAH1A REV. C)
• A photo of the label
• Turbine model and Mark control generation
• Quantity
• Urgency — planned outage or unplanned downtime

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