Servo valve control on Mark VIe: the role of IS220PSVOH1B

Every hydraulically actuated valve on a GE Speedtronic Mark VIe machine needs something to convert a digital position command into a precise coil current, and on many units that job belongs to the servo output pack. The IS220PSVOH1B performs it by interfacing one or two IONet Ethernet networks to the TSVO servo terminal board and driving up to two servo valve position loops through the WSVO servo driver. It carries its own processor, local power supply, flash and RAM, an internal temperature sensor, and a servo acquisition board, and it is set up and diagnosed entirely in ToolboxST.

In practice the pack lives at the machine, bolted to the TSVO board, closing the loop between commanded and actual valve position. Its faceplate LEDs (PWR, ATTN, the ENet link and status indications, and the ENA enables) and the ToolboxST diagnostics are where any investigation should begin.

Rule out the cheaper causes first

The single most useful habit when a servo loop misbehaves is to resist swapping the pack first. An IS220PSVOH1B is rarely the cause of these classic symptoms:

• Actuator will not move: suspect a jammed or contaminated servo valve, an open coil, or a lost drive connection at the TSVO board before the pack.
• Position hunts or drifts: almost always a feedback problem — a failing LVDT/LVDR, a wet or loose feedback connector, or damaged field wiring.
• Pack shows offline: check the IONet cable, the switch port, and the power feed; the ENet and PWR LEDs isolate this quickly.
• New pack looks dead: if you just changed the TSVO board, confirm you manually reconfigured the pack — it does not auto-reconfigure after a terminal-board change.

Use ToolboxST to compare commanded current with actual and to check feedback health. If drive and feedback are both good at the terminal board and the pack still faults, then replacing the IS220PSVOH1B is justified.

Why the H1B matters when you replace a servo pack

Read the number as IS220 (Mark VIe distributed I/O platform), PSVO (servo output function), and H1B (hardware revision and variant). The H1B is a later revision than the H1A, and both are in the field. Because revisions can differ in ways that matter to your ControlST/ToolboxST version, order the exact suffix you are replacing and verify compatibility rather than assuming interchangeability. Our GE Speedtronic Part Number Decoder breaks down what each segment of the number represents.

Companion parts and cross-generation notes

The servo pack rarely travels alone in a spares plan. Explore the GE Speedtronic Turbine Control Boards and GE Mark VI IS200 Boards collections for the analog, discrete, and protection packs that share the Mark VIe IONet. If you are weighing an upgrade from a legacy control, the Mark V vs Mark VI: DS200 to IS200 guide outlines how servo and I/O hardware changed between generations.

Information to include when you request a quote

The more of this you send, the faster and more accurate the quote:

• Full part number with suffix (IS220PSVOH1B) and the printed board revision.
• A clear photo of the unit label.
• Turbine model and control generation (Mark VIe or Mark VI).
• Quantity required and how soon you need it.

This unit is new surplus in the factory package; the condition and warranty exactly as offered are shown in the table below.

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