Key Technical Specifications
| Parameter | Specification |
|---|---|
| Model | IS220PDOAH1A |
| Alternate Part No. | 336A4940CSP2 (as listed by suppliers) |
| Product Family | GE Speedtronic Mark VIe Discrete Output I/O Pack |
| Relay Channels | Up to 12 discrete outputs (depends on terminal board) |
| Response Time | Approx. 6 ms from Ethernet command to output |
| Supply Voltage | 28 V DC nominal via 3-pin connector |
| Communication | 2× RJ45 I/O Ethernet ports (IONet) |
| Terminal Board Interface | DC-37 connector to TRLY/SRLY boards |
| Compatible Boards | TRLYH1B/C/D/F, TRLYH1E, SRLY-type boards; not DRLY DIN-rail boards |
| Diagnostics | LEDs for power, attention, Tx/Rx, link; infrared local diagnostic port |
| Memory | Flash and RAM on processor board |
| Dimensions | Approx. 3.25 × 1.65 × 4.78 in (83 × 42 × 121 mm) |
| Typical Applications | GE turbine control, Mark VIe Simplex/Dual/TMR discrete output paths |
Product Introduction
IS220PDOAH1A is the kind of Mark VIe pack you do not notice until a trip relay refuses to drop or a permissive output stays stuck. It sits on a TRLY or SRLY terminal board and converts Mark VIe I/O Ethernet commands into discrete relay actions — fuel valves, lube-oil permissives, breaker commands, fan starts, alarm relays, that sort of work.Engineers keep this pack in the spare rack because it is simple, deterministic, and easy to verify. The processor board is shared across Mark VIe I/O packs, while the acquisition board is specific to discrete output duty. On power-up it runs self-tests, reads the terminal-board ID chip, loads application code from flash, and only then enables outputs. That sequence prevents random relay chatter during boot. The 6 ms response figure is not fast by motion-control standards, but for turbine permissives and auxiliary relay logic it is more than adequate. Just make sure the terminal-board type matches; the pack checks this electronically and will refuse to play nice if the ID does not match.
Quality SOP & Tech Pitfalls
The Lab Report (SOP)
- Nameplate verification: Confirm IS220PDOAH1A, revision, and serial. Check for 336A4940CSP2 if listed.
- Visual inspection: Inspect DC-37 connector pins, RJ45 ports, 3-pin power connector, conformal coating, and mounting studs.
- Power-on self-test: Apply 28 V DC and verify LED boot sequence: power, self-test, attention, link.
- Ethernet link check: Confirm ENET1/ENET2 link LEDs and communication with the Mark VIe controller or test rack.
- Terminal-board ID check: Verify the pack reads the terminal-board ID correctly; mismatch blocks output enable.
- Output verification: Command individual relay channels through ToolboxST or the controller and confirm coil feedback where supported.
- Insulation and supply check: Measure supply input and coil-side insulation with a Fluke 115 or equivalent.
- Firmware/logging: Record firmware revision, application code version, and I/O network address.
- ESD packing: Seal in anti-static bag with desiccant and rigid foam.
The Engineer’s Warning (Pitfalls)
- Wrong terminal board = dead outputs. IS220PDOAH1A works with TRLY/SRLY boards, not DRLY DIN-rail boards. If someone swapped the terminal board during a previous outage, the new pack may boot but never enable outputs.
- TMR packs are not single-pack swaps. In a TMR application, all three packs must match in revision, firmware, and configuration. Replacing one pack with an unmatched revision can cause voting faults.
- Do not force the DC-37 connector. These packs plug straight into the terminal board. If it does not seat cleanly, the mounting bracket or stud alignment is wrong. Forcing it bends pins and creates intermittent relay failures months later.
- Outputs stay disabled until self-tests pass. If the pack shows power but no outputs, check terminal-board ID match, Ethernet communication, and application-code load before condemning the relays.
Installation & Configuration Guide
1. Pre-Installation ⚠️
- Confirm with operations that relay outputs can be safely disabled.
- Photograph existing pack revision, terminal-board type, Ethernet port assignments, and relay wiring.
- Record I/O network addresses and ToolboxST configuration.
- Verify the replacement pack revision matches the existing Mark VIe configuration.
2. Removal
- Disable affected outputs in the controller or place the system in a safe maintenance state.
- Disconnect the 3-pin power connector.
- Unplug Ethernet cables and label ENET1/ENET2.
- Remove the mounting studs and carefully withdraw the pack from the terminal board.
3. Installation
- Confirm the terminal-board type matches IS220PDOAH1A requirements. This prevents most startup failures.
- Inspect the DC-37 connector for bent pins or contamination.
- Seat the pack firmly and evenly onto the terminal board.
- Install and tighten the mounting studs without applying side load to the connector.
- Reconnect Ethernet cables to the correct ports.
- Reconnect the 3-pin 28 V DC supply.
4. Power-On & Testing
- Apply power and observe the LED boot sequence.
- Verify Ethernet link on ENET1/ENET2.
- Confirm the pack reads the terminal-board ID and loads application code.
- Test each relay channel under supervision.
- Verify feedback signals and alarm indications in ToolboxST or the controller.
- Document the new pack revision and firmware for the maintenance log.
Compatible Replacement Models
| Compatibility | Model / Order Code | Notes |
|---|---|---|
| ✅ Drop-in Replacement | IS220PDOAH1A | Exact match. Verify revision and terminal-board pairing. |
| ⚠️ Revised Pack | IS220PDOAH1B | Later revision. May support additional terminal boards; confirm with GE documentation before substitution. |
| ⚠️ Coated Variant | IS221PDOAH1B | Conformal-coated version for harsher environments. Verify terminal-board compatibility. |
| ⚠️ Combined I/O Option | IS220PDIOH1A | Discrete input + output pack. Not a direct PDOA replacement without configuration review. |
| ❌ Not Interchangeable | IS220PDIAH1A | Discrete input pack only. Cannot replace a discrete output pack. |
| ❌ Not Interchangeable | IS220YDOAS1A | Mark VIeS safety discrete output pack. Requires safety-system approval and matching architecture. |
Frequently Asked Questions (FAQ)
Q: Can I hot-swap an IS220PDOAH1A while the turbine is running?
Not without a proper maintenance procedure. The pack supports field replacement, but the outputs it controls may trip valves, breakers, or auxiliaries. Always coordinate with operations and disable or bypass affected outputs first.Q: What terminal boards does IS220PDOAH1A support?
It supports TRLY and SRLY-type discrete output terminal boards, including TRLYH1B/C/D/F and TRLYH1E variants. It does not support DRLY DIN-rail boards.Q: Why do all relay outputs stay off after replacement?
Most likely causes are terminal-board ID mismatch, missing Ethernet communication, failed self-test, or incorrect revision. The pack will not enable outputs until it validates the terminal board and loads application code.Q: Is IS220PDOAH1A the same as IS220PDIOH1A?
No. PDOA is discrete output only. PDIO combines discrete input and discrete output functions. Swapping them requires configuration changes and terminal-board verification.Q: What voltage does it run on?
Nominal 28 V DC through the 3-pin power connector. Some references mention 24/28 V DC ranges, but treat the physical nameplate and GE manual as final.Q: Does it output 4–20 mA or Modbus?
No. It is a discrete relay output pack driven over Mark VIe I/O Ethernet. If you need analog outputs or serial communication, you need a different I/O pack.Q: How do I know if the pack is healthy?
Check the LEDs for power, link, and attention status; verify Ethernet communication; confirm terminal-board ID recognition; and test relay channels through ToolboxST. A steady attention LED usually means a configuration or hardware mismatch.
