IS220PAOCH1A: eight-channel analog output for Mark VIe

The IS220PAOCH1A is the analog output (PAOC) I/O pack in the GE Speedtronic Mark VIe family. It provides the electrical interface between one or two IONet Ethernet networks and an analog output terminal board, and it delivers eight simplex 0-20 mA current-loop outputs with current feedback on every channel. Typical loads are valve positioners, I/P transducers, and indicators; each output has 18 V of compliance and drives customer loads up to roughly 900 ohms. A BPPx processor board and a matched acquisition board handle the work, with dual RJ-45 Ethernet connectors, a three-pin power input, and a DC-37 connector to the terminal board.

Inside the PAOC: DAC, current feedback, and the enable relay

Knowing the signal chain makes troubleshooting far easier. Each output is set by a 16-bit digital-to-analog converter that commands an external transistor amplifier to source the loop current. Current feedback is sensed on a burden resistor on the terminal board and digitized by a 16-bit analog-to-digital converter, so the pack constantly compares commanded against actual current. Every channel also has a mechanical, normally-open enable relay: when it is de-energized the loop opens between the pack output and the customer load, and a faceplate LED reflects the relay position. An internal temperature sensor and a set of power-up and runtime self-tests round out the design.

Before you replace the pack: where analog-output faults really come from

A stuck or wrong 0-20 mA signal often looks like a failed PAOC when the cause is really in the loop. Work through these before ordering an IS220PAOCH1A:

• How many channels are affected? One bad channel usually means field wiring, the load device, or that channel's terminal-board circuit. All channels unhealthy with a valid command points instead at a pack or terminal-board hardware failure.
• Field wiring and load: an open loop, a high-resistance connection, or a load beyond the compliance limit reads as a failed output. Check the wiring and connectors first.
• The terminal board and burden resistor: current feedback depends on that resistor; a bad burden or terminal-board fault makes feedback disagree with command even though the DAC is fine.
• Enable relay state: if the channel relay is de-energized by logic or fault, the loop is open by design — confirm the relay LED before condemning the electronics.
• IONet and power: a network or power-feed problem drops the whole pack; the diagnostic LEDs isolate this.

GE's own guidance is a good tiebreaker: ensure the command sits between 0 and 20 mA, verify feedback agrees with command, and inspect field wiring and connectors. If every active output reports unhealthy feedback against a valid command, a board failure is likely and the terminal board and I/O pack are replaced together.

Part number and the H1A / BPPB revision

The number decodes as IS220 (Mark VIe distributed I/O platform), PAOC (analog output current function), and H1A (hardware revision and variant). The PAOCH1A is built around the BPPB processor board; the later PAOCH1B uses a functionally compatible BPPC processor and requires ControlST software V04.06 or later. Match the suffix to your installed pack and confirm the ControlST version before you order. For a full walkthrough of Speedtronic numbering, see our GE Speedtronic Part Number Decoder.

Related analog and control I/O packs

The PAOC pairs with GE analog output terminal boards and sits alongside the other IS220 packs on the same IONet. Browse the GE Mark VI IS200 Boards and GE Speedtronic Turbine Control Boards collections for companion analog input, discrete, servo, and protection hardware. If you are comparing control generations, the Mark V vs Mark VI: DS200 to IS200 guide is a useful reference.

What to include in your PAOC quote request

To confirm the exact unit, send us:

• Full part number and suffix (IS220PAOCH1A) plus the revision on the label.
• A photo of the pack nameplate.
• Turbine model and Mark VIe or Mark VI generation.
• Quantity and how urgent the need is.

This unit is used, cleaned and tested, with a 1-year warranty; the exact condition wording is in the table below.

Request a quote for this PAOC pack

Send the details above via Request a Quote and expect a response within 24 hours. We ship worldwide on DDP terms and accept purchase orders from qualified organizations.