The IO Engine CPU in a Mark V LM panel

Every analog I/O core in a GE Speedtronic Mark V LM panel is run by its own processor card, and this is that card: the DS200UCPB IO Engine CPU board, in its G5A catalog form with revision suffix AFB. The Mark V LM is the Speedtronic variant GE built for its aeroderivative gas turbine packages — the platform manual's own board list includes LM6000-specific modules — and it distributes intelligence differently from the heavy-duty Mark V. Instead of three voting control processors, an LM panel pairs one central Control Engine with four IO Engines, designated <R1>, <R2>, <R3>, and <R5> in GE's documentation, each running on one UCPB.

GE's function manual for the platform, GEH-6153, lays the arrangement out plainly: the UCPB is a daughterboard mounted on the DS200STCA Turbine Communication Board in location 1 of the core, it carries the IO Engine's 80486DX processor, and it acts as the IO "switchboard" between the Control Engine and the I/O cards. Signal conditioning happens on boards such as the TCQA; the UCPB packages the conditioned data and broadcasts it on the COREBUS, the controller's internal ARCNET network, with critical values sent in fast packets every 10 ms and lower-priority values at a slower rate. Traffic from the digital and protective cores reaches the IO Engine over a separate serial link, the IONET, with the STCA beneath this board acting as network master.

Not a relay board: read the symptom correctly

Surplus catalogs have filed this part number under some loose labels over the years — including, as on this listing's original description line, "turbine control relay board." Take the function from the manual, not from the label. Contact outputs in a Mark V LM are switched by DS200TCRA relay boards in the digital cores; the UCPB switches data, not contacts. That distinction sorts your troubleshooting immediately: a stuck or dead contact output belongs to the TCDA/TCRA path and its termination boards, while an analog core that has gone silent — every value the core owns stale at once, the Control Engine logging loss of communication with one IO Engine — belongs on the UCPB's shortlist.

Shortlist, not verdict. Before you order, spend ten minutes ruling out the neighbors:

• Core power. The TCPS power supply board sits in location 5 of the same core, and a failed supply imitates a failed processor perfectly. Check it first.
• COREBUS path. Inspect the ARCNET drop and BNC connections serving that core. A cable fault silences a core just as thoroughly as a dead CPU.
• Address switches. The COREBUS address of each IO Engine is set by DIP switches on the UCPB. If hardware has been disturbed recently, verify the setting against the site drawings.
• Reboot once. GE's recommended method is a hard reboot using the core's power switch. Watch whether the IO Engine rejoins the bus.

From the operator interface, the MON_SYS pages documented in GEH-6153 show COREBUS link status and I/O packet reception. One silent core implicates that core's UCPB, STCA, supply, or cabling; a COREBUS that is down everywhere points instead at the Control Engine end of the link. That check alone can keep you from replacing the wrong board.

Decoding DS200UCPBG5AFB

GEH-6153 prints the key to DS-series numbering, and it reads like this. DS identifies GE's Salem, Virginia board operation. 200 marks a base-level board, where 215 would mark a higher-level assembly with added components such as PROMs. UCPB is the functional acronym. G5 is the group variation — G and H denote different groups, never interchangeable on faith. The first letter after the group, A, is a functional revision that is not backward compatible; it is effectively part of the catalog number, which is why the orderable part here is DS200UCPBG5A. The remaining letters — F and B — record backward-compatible functional and artwork revisions. Match the group and catalog number exactly; treat the tail letters as revision history to report with your inquiry. The full logic is walked through in our GE Speedtronic Part Number Decoder.

The hardware around it

If the UCPB does prove faulty, its neighbors are worth knowing — both for diagnosis and because panel work is the natural moment to review spares:

• DS200STCA — Turbine Communication Board, the motherboard the UCPB mounts on and the IONET master.
• DS200TCQA — analog control I/O board handling servo, LVDT, thermocouple, milliamp, and vibration signals in the same core.
• DS200TCPS — the core's power supply board.
• DS200TCEA — the triple-redundant protective processors, voted two-out-of-three, in the protective core.

We stock these alongside the UCPB in our GE Mark V DS200 Boards collection; the wider Speedtronic range is in GE Speedtronic Turbine Control Boards. For how the DS200 generation relates to what came after it, see Mark V vs Mark VI: DS200 to IS200.

What to put in your quote request

1. The complete part number from the board label, including the revision letters — DS200UCPBG5AFB rather than just UCPB.
2. A photo of the label, if the panel is accessible. It prevents transcription errors.
3. Your turbine package and control system — Mark V LM, or heavy-duty Mark V Simplex or TMR — plus which core the board serves.
4. The symptom that led you here, so we can flag mismatches before shipping.
5. Quantity and urgency: breakdown, planned outage, or shelf spare.

How we supply it

The board on this page is a used DS200UCPBG5A (revision AFB), cleaned and tested, with a one-year warranty as stated below. Send the details above through the Request a Quote button and you will have our response within 24 hours. We ship worldwide on DDP terms, so customs and delivery to your plant are handled by us, and we accept purchase orders from qualified companies.