IS220PDOAH1A: Discrete Output Pack for Mark VIe Turbine Control

The IS220PDOAH1A is the discrete output pack in GE's Speedtronic Mark VIe distributed I/O architecture. Like every IS220-series pack, it is not a rack card — it mounts directly on a discrete output terminal board and exchanges data with the <R>, <S>, or <T> controller over the I/O Ethernet network (IONet) through dual RJ-45 ports. A processor board common to all Mark VIe I/O packs pairs with an acquisition board built specifically for driving relay outputs.

PDOA controls up to 12 relay outputs and reads feedback signals back from the terminal board through a single DC-37 pin connector. Depending on which terminal board is installed, it drives either electromagnetic relays (on TRLYH1B, C, D, or F boards) or solid-state relays (on TRLYH1E boards) — the pack itself is the same, but the terminal board sets which relay technology is actually in the circuit. Power comes in through a 3-pin connector with built-in soft-start current limiting, and status LEDs plus a local infrared diagnostic port support field troubleshooting.

One behavior worth knowing before you troubleshoot: on power-up, every output stays disabled until the pack completes its internal self-tests, and the enable path is deliberately independent of the command path so relays stay dropped out during initialization. That's fail-safe design, not a fault.

Is It the Pack, or Is It Downstream?

• A relay that won't pick up, or a feedback signal that doesn't match the command, is very often the field wiring, the relay contact itself, a blown fuse, or a loose terminal on the TRLY board — not the PDOA pack, which only carries the command and monitoring electronics.
• Use the swap test: move the suspect pack to a known-good terminal board (or a known-good pack to the suspect board) and see which one the fault follows. This is the standard way to confirm a pack failure before ordering a replacement.
• Don't mistake the power-up self-test sequence — outputs briefly dropped out while the pack initializes — for a hardware failure.
• Confirm relay technology match: a TRLYH1E (solid-state) board is not wired like a TRLYH1B/C/D/F (electromagnetic) board, and installing the wrong assumption about relay type can look like a pack problem when it isn't.
• Check the IONet path — both Ethernet ports, cabling, and switch health — before condemning the pack, since a lost network connection presents the same way a dead pack does.
• In a TMR configuration, confirm which of the three cores is actually alarming before pulling hardware; a single pack fault inside a healthy voted triad is a different situation from a simplex output failure.

Reading the IS220PDOAH1A Part Number

IS220 marks this as a Mark VIe distributed I/O pack, PDOA is the discrete output function, H1 is the design generation, and the trailing A marks a hardware/processor revision. Treat the full string as the part number — suffix and revision both need to match your terminal board and ControlST configuration. Our GE Speedtronic Part Number Decoder explains how each segment is built.

Related Packs and Terminal Boards

PDOA pairs with TRLY-family relay terminal boards. If your panel uses a combined input/output terminal board instead of separate discrete input and output boards, the equivalent single-pack solution is PDIO, which handles both functions from one pack. See our GE Mark VI IS200 Boards collection to check compatible terminal boards.

Information We Need for a Quote

• Full part number with suffix (IS220PDOAH1A)
• A photo of the label
• Turbine model and Mark control generation
• Quantity
• Urgency — planned outage or unplanned downtime

We respond to every quote request within 24 hours, ship worldwide DDP, and accept purchase orders. This is a request-a-quote store — no prices are posted online, and every order is confirmed by our team before it ships.

General Information about the Product
Part Number	IS220PDOAH1A Mark VI IS220
Description	GE General Electric IS220PDOAH1A I/O Module Mark VI
Condition	used Clean and Tested. With 1 Year Warranty.