An Analog Output Card for GE's First TMR Turbine Control System

The DS3800NDAC is the analog output board in GE's Speedtronic Mark IV control system, the first Speedtronic platform built around triple modular redundant (TMR) control. Mark IV panels ran three independent controllers, referred to in the system documentation as <R>, <S>, and <T>, alongside a <C> communications processor, with two-out-of-three voting on every output. The DS3800NDAC's job inside that architecture is to take the digital command values calculated by the control system and turn them into the analog voltage or current signals that drive final control elements — valves, actuators, and similar devices on the turbine and its auxiliaries. This DS3800NDAC1A1A unit is an earlier production run/revision within the NDAC line (the "1A1A" designation identifies its specific run and revision), supplied used, cleaned, and tested, with a 1-year warranty as detailed in the table below.

Rule Out These Causes Before You Order a Replacement Board

Analog output problems on a Mark IV panel don't automatically mean the NDAC card has failed. Because the board sits at the tail end of a signal chain that starts with sensors and math in the <R>/<S>/<T> processors and ends at a physical actuator, a bad reading or a valve that won't respond can originate in several places other than this card:

• Field wiring and terminal boards — loose terminations, corroded ribbon-cable connectors, or a damaged run between the rack and the actuator can mimic a dead output channel. Technicians experienced with Mark IV racks routinely check connector continuity and ribbon-cable seating before condemning a card.
• The actuator or servo itself — a stuck valve, a failed positioner, or a feedback device (such as an LVDT) reporting bad data can look exactly like a control-signal problem even though the analog output from the rack is correct.
• Upstream power quality — the DS3800NDAC, like every card in the rack, depends on clean, regulated power from the panel's supplies. Voltage sag or noise upstream can produce symptoms that look like a card fault and disappear the moment power is corrected — without any card ever being replaced.
• A single-channel voting mismatch — because Mark IV uses two-out-of-three voting across <R>, <S>, and <T>, a genuine fault on just one control channel may show up as a diagnostic alarm without ever tripping the unit. Confirm which channel the diagnostic actually points to before pulling the card that seems most convenient.

If you've checked wiring, the actuator/feedback loop, and panel power, and the fault still traces back to this specific slot, a replacement DS3800NDAC is the right call.

What the DS3800NDAC1A1A Part Number Tells You

GE's Speedtronic boards follow a consistent naming pattern: the DS3800 prefix identifies the base board family, the four letters that follow (NDAC) identify its function — in this case, analog output — and the trailing characters identify the specific production run and engineering revision. On this unit, "1A1A" is that run/revision identifier. GE did not publish a public decoder for what changed between each letter combination; what's documented is that later runs and revisions on the same functional board are not automatically interchangeable with earlier ones, and the manufacturer's own part-number conventions are typically referenced in the Renewal/Warranty Replacement section of the hardware manual for the system. In practice, this means you should treat the suffix as part of the part number, not an optional detail — order to match what's stamped on your existing board's label, or confirm compatibility with someone who has the manual for your specific unit before assuming any DS3800NDAC will drop in.

For a broader walkthrough of how GE Speedtronic part numbers are structured across Mark IV, Mark V, and Mark VI families, see our GE Speedtronic Part Number Decoder.

Where the NDAC Fits Among Its Companion Boards

The DS3800NDAC doesn't work alone. On the input side of the same analog chain, the DS3800NADA performs the complementary analog-to-digital conversion, and other "N"-prefixed boards in the DS3800 line — current-loop input and thermocouple input cards among them — round out the analog signal conditioning used throughout a Mark IV panel. If your troubleshooting points to an analog signal problem but you're not certain the fault is specifically on the output side, it's worth confirming against your panel's elementary diagrams which board actually carries the loop in question before ordering. Our GE Mark IV DS3800 Boards collection covers the wider family if you need to cross-check part numbers, and our Mark V vs Mark VI: DS200 to IS200 guide is useful background if your site is migrating off Mark IV hardware entirely.

What to Send Us for a Fast, Accurate Quote

To get you an accurate 24-hour quote on a DS3800NDAC1A1A, include:

• The complete part number exactly as it appears on the board label, including the full suffix
• A photo of the label if you have any doubt about a character or revision letter
• Your turbine model/frame and confirmation that the system is Mark IV Speedtronic
• Quantity needed and whether this is for spares stock or an active outage

We ship worldwide on a DDP basis, so duties and import formalities are already handled on arrival, and we accept purchase orders. Use the Request a Quote button on this page and we'll respond within 24 hours.

General Information about the Product
Part Number	DS3800NDAC1A1A Mark IV DS3800
Description	DS3800NDAC1A1A by GE General Electric DS3800NDAC Analog Output Board Mark IV
Condition	used Cleaned and Tested. With 1 Year Warranty.