Key Technical Specifications
| Parameter | Specification |
|---|---|
| Function | Discrete output I/O pack for Mark VIe |
| Channels | Up to 12 relay outputs, depending on terminal board |
| Compatible Terminal Boards | TRLY and SRLY types; not for DIN-rail DRLY boards |
| Network Interface | 2x RJ45 Ethernet ports |
| Power Input | 3-pin DC connector, typically 28 VDC |
| Field Connector | DC-37 connector to terminal board |
| Response Time | Approximately 6 ms from Ethernet command to output |
| Diagnostics | Power, Attention, Tx/Rx, Link LEDs; infrared serial port |
| Control Modes | Simplex, Dual, or TMR when used with multiple packs |
| Condition | New original / new surplus depending on supplier |
Product Introduction
The GE IS220PDOAH1A is a discrete output pack for the Speedtronic Mark VIe turbine and industrial control platform. It sits between the I/O Ethernet network and the field relay terminal board, turning controller commands into hardened discrete outputs. Each pack supports up to 12 relay channels and receives terminal-board-specific feedback so the controller can confirm output state.This is not a generic relay module. It is a Mark VIe distributed I/O pack with its own processor board, application firmware, Ethernet stack, and diagnostic interface. It is commonly used in simplex, dual, or TMR configurations, and it mates with electromagnetic or solid-state relay terminal boards such as TRLY and SRLY types. The ~6 ms response time is acceptable for turbine trip logic, auxiliary relay control, permissive signaling, and plant interlocks where deterministic behavior and diagnostic visibility matter more than raw channel density.
Quality SOP & Tech Pitfalls
The Lab Report (SOP)
- Visual inspection: chassis, DC-37 connector, Ethernet ports, power connector, LED window, and serial label.
- Part-number verification: confirm IS220PDOAH1A and 336A4940CSP2 match the purchase record.
- Connector inspection: check DC-37 pins, RJ45 ports, and 3-pin power connector for bent pins or corrosion.
- Power-up test: apply rated DC supply and verify Power, Link, and Attention LEDs.
- Ethernet link test: confirm communication on ENET1/ENET2 with a Mark VIe controller or test rack.
- Diagnostic port check: verify infrared serial communication if supported by the firmware load.
- Output verification: confirm relay command response and feedback path with the correct terminal board.
- ESD-safe packaging, moisture barrier bag, and shock-protected crating.
I would not deploy this pack without confirming the terminal-board type. The PDOA pack reads the terminal-board ID, and a mismatch can produce incorrect feedback or inhibited outputs.The Engineer’s Warning (Pitfalls)
- Terminal-board mismatch: IS220PDOAH1A works with approved TRLY/SRLY terminal boards but not with DIN-rail DRLY boards.
- Firmware revision: Replacement packs must support the existing Mark VIe application load. A different firmware revision can change startup behavior or diagnostic flags.
- Simplex vs TMR confusion: Swapping a TMR pack into a simplex slot, or vice versa, can cause persistent faults even if the hardware appears functional.
- Feedback dependency: The pack relies on terminal-board feedback. A failed terminal board, wiring fault, or relay coil issue can look like a bad PDOA pack.
- Part-number formatting: “3364940CSP2” is commonly documented as “336A4940CSP2.” Treat them as related, but confirm the exact label on the unit.
I have seen PDOA replacements rejected during commissioning because the terminal board ID did not match the expected type. The pack was healthy. The system refused to trust the output path.
Installation & Configuration Guide
Pre-Installation
- Confirm the Mark VIe configuration: simplex, dual, or TMR.
- Photograph existing Ethernet cabling, power wiring, DC-37 connection, and LED status.
- Record firmware revision, terminal-board type, and active fault history.
- Verify that the replacement pack matches the OEM bill of materials.
Removal
- Follow plant safety and turbine-control procedures before removing I/O power.
- Label Ethernet cables, power leads, and terminal-board connections.
- Remove the mounting hardware near the Ethernet ports.
- Disconnect the DC-37 connector and power plug carefully.
Installation
- Install the correct terminal board first and confirm it is securely mounted.
- Seat the IS220PDOAH1A pack directly into the terminal-board connector.
- Secure the pack using the threaded studs near the Ethernet ports.
- Reconnect the 3-pin DC power input and Ethernet cables.
- Verify that ENET1/ENET2 match the network assignment, especially in dual or TMR systems.
Power-On & Testing
- Apply DC power and confirm normal LED indications.
- Verify Ethernet link status on both ports if dual networking is used.
- Check diagnostic feedback through the controller or infrared port.
- Test each relay output under controlled conditions.
- Confirm feedback consistency before returning the system to automatic control.
Compatible Replacement Models
- GE IS220PDOAH1A (336A4940CSP2) — Direct replacement for existing Mark VIe discrete output applications. Match terminal-board type and firmware.
- GE IS220PDOAH1B — Later or variant discrete output pack for Mark VIe. May support additional terminal-board types, including some solid-state relay boards. Requires configuration verification.
- GE IS220YDOAS1A — Safety discrete output pack for Mark VIeS applications. Not a direct drop-in replacement unless the system is designed for safety-rated outputs.
Frequently Asked Questions (FAQ)
What does IS220PDOAH1A do?
It is a Mark VIe discrete output pack that drives up to 12 relay channels and reports output status back to the controller through a matched terminal board.Is 3364940CSP2 the same as 336A4940CSP2?
They refer to the same part family. The standard GE format is 336A4940CSP2. Always confirm the exact label on the unit before treating it as a drop-in replacement.Which terminal boards can it use?
It is compatible with approved TRLY and SRLY discrete output terminal boards. It is not intended for DIN-rail DRLY boards.Can it be used in TMR systems?
Yes. In TMR mode, three PDOA packs are typically used, each with its own network connection.What is the output response time?
Approximately 6 ms from Ethernet command to output, depending on system configuration.Does it replace IS220PDIAH1A or IS220PDIOH1A?
No. PDIA is a discrete input pack, and PDIO combines discrete input and output functions. PDOA is discrete output only.What warranty is reasonable?
A 12-month warranty is common for new or factory-sealed industrial spares, but terms vary by supplier and condition code. Confirm warranty, revision, and return policy in writing before purchase.
