What the PAOC analog output pack does

When a Mark VIe controller needs to send a precise current signal out to the plant — to a valve positioner, an I/P converter, or a remote indicator — it hands the job to the analog output pack. This IS220PAOCH1A provides eight simplex 0-20 mA outputs, each with its own current feedback, and forms the electrical bridge between one or two IONet Ethernet networks and a GE analog output terminal board. Power arrives on a three-pin input with a built-in soft-start that limits inrush, so you do not have to remove power before plugging in the cable; a DC-37 connector carries the signals to the terminal board. Configuration is done in ToolboxST.

Diagnosing a dead or drifting analog output

The most expensive mistake with analog outputs is swapping the pack before checking the loop. An IS220PAOCH1A reports feedback on every channel, and that feedback is your best clue:

• Single channel wrong: start at the field — wiring, connectors, the load device, and that channel's circuit on the terminal board. A load beyond the pack compliance will not hold the commanded current.
• All channels wrong with a valid command: this pattern points to a pack or terminal-board hardware fault rather than the field.
• Feedback disagrees with command: the current is sensed across a burden resistor on the terminal board; a bad resistor or terminal-board fault skews the reading even with a healthy converter.
• Output shows open: check the per-channel enable relay — when de-energized it deliberately opens the loop, and an LED shows its state.
• Pack offline: look to the IONet cabling and the power feed before the electronics.

The pack runs continuous self-tests — power-supply monitoring, an electronic-ID check that the CPU, acquisition, and terminal boards match, and a comparison of sensed current against the command. Reading those diagnostics in ToolboxST usually tells you whether the fault is the pack or something around it.

New surplus factory package explained

This IS220PAOCH1A is offered as new surplus in the factory package (NSFP): unused inventory in its original packaging, well suited to a critical shelf spare. We describe condition plainly and never inflate it; the exact wording and warranty for this specific unit appear in the table below.

Matching the suffix: H1A versus H1B

The suffix is not decorative. IS220 is the Mark VIe distributed I/O platform, PAOC is the analog output function, and H1A is the hardware revision. The H1A carries a BPPB processor board; the H1B carries a functionally compatible BPPC processor and needs ControlST V04.06 or later. Order the revision that matches your system, and confirm your software version if you are considering the other. Our GE Speedtronic Part Number Decoder shows how the segments map to hardware.

Companion terminal boards and related packs

The PAOC mounts to a GE analog output terminal board and shares its IONet with the rest of the IS220 lineup. For companion parts — analog input, discrete I/O, servo, and protection packs — see the GE Speedtronic Turbine Control Boards and GE Mark VI IS200 Boards collections. Planning a control upgrade? The Mark V vs Mark VI: DS200 to IS200 guide compares the platforms.

Quote request checklist

Please provide:

• Complete part number with suffix (IS220PAOCH1A) and the board revision.
• A photo of the unit label.
• Turbine model and control generation (Mark VIe or Mark VI).
• Quantity and timing, including any outage window.

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