Where the UCPB sits in the Mark V LM architecture

GE's function manual for the Mark V LM, GEH-6153, describes the DS200UCPB in one phrase field engineers recognize immediately: it acts as the IO "switchboard" between the Control Engine and the I/O cards. The Mark V LM — the Speedtronic variant GE supplied with its aeroderivative turbine packages — concentrates sequencing and control in a single Control Engine core and delegates I/O to four IO Engines, named <R1>, <R2>, <R3>, and <R5> in the documentation. Each IO Engine is a card rack whose location 1 holds a DS200STCA Turbine Communication Board; the UCPB is the daughterboard mounted on that STCA, and it carries the 80486DX processor that runs the IO Engine.

Alongside the CPU, supplier documentation for this G6A version lists a SIMM socket with DRAM, flash EPROM holding the ROM BIOS, two RS-232 serial ports, and an ARCNET driver — the interface that puts the IO Engine on the COREBUS, the panel's internal ARCNET network. Analog boards such as the TCQA condition the raw signals; the UCPB packages the values and broadcasts them to the Control Engine on a task schedule, fast packets on a 10 ms cadence for critical data and slower packets for the rest. Digital and protective-core traffic arrives over the IONET serial network, for which the STCA is master. Outputs computed by the Control Engine return over the COREBUS each frame, and the UCPB hands them back to the I/O boards.

Symptoms that point to the IO Engine — and symptoms that do not

Correct diagnosis here is mostly a question of scope. A single suspicious signal — one thermocouple pegged, one servo output misbehaving — is almost never the UCPB; that points at the I/O board handling the channel, its termination board, or field wiring. The UCPB failure signature is core-wide: every value owned by one IO Engine goes stale simultaneously, the Control Engine raises communication diagnostics against that engine, and the other cores carry on normally.

Even then, three cheaper suspects come first. The TCPS power supply in location 5 of the same rack can drop and take the whole core down with it. The COREBUS drop cable and its BNC connections can fail after decades of vibration and heat, silencing a healthy processor. And if anyone has recently handled the board, the DIP switches that set the IO Engine's COREBUS address may simply be wrong. GEH-6153's troubleshooting chapter gives you tools to scope the problem from the operator interface: the MON_SYS pages report COREBUS link status and packet reception per core, and a hard reboot via the core's power switch is GE's sanctioned way to force a fresh start. If one engine still refuses to join the bus with power confirmed good and cabling ruled out, the STCA/UCPB pair is where attention lands — we can quote the daughterboard alone or both boards together.

Reading the number: G6A plus FB

Per the part-numbering key GE prints in the Mark V LM manual: DS marks the Salem, Virginia board line; 200 a base-level assembly; UCPB the functional acronym; G6 the group variation. The letter immediately after the group — A — is a functional revision that is not backward compatible, which makes DS200UCPBG6A the effective catalog number. The trailing FB letters are backward-compatible functional and artwork revisions: relevant history, rarely a barrier within the same catalog number. What you should not do is treat groups as interchangeable — a G5A and a G6A are different catalog items, and an H-group would be different again. Our GE Speedtronic Part Number Decoder covers the scheme across the whole DS200 range.

Companion boards on the same rack

Orders for the UCPB frequently travel with its neighbors, either as suspects eliminated late or as spares bought while the panel is open:

• DS200STCA — the motherboard beneath it, IONET master, synchronization check.
• DS200TCQA and DS200TCQC — analog I/O board and expander in the same core.
• DS200TCPS — rack power supply, location 5.
• DS200TCDA and DS200TCRA — digital I/O and relay output boards reached over the IONET.

Browse them in GE Mark V DS200 Boards, or the full Speedtronic line in GE Speedtronic Turbine Control Boards. If your site is weighing longer-term support against migration, Mark V vs Mark VI: DS200 to IS200 lays out how the generations map.

Details that get you an accurate quote in one pass

1. The full number off the label — DS200UCPBG6AFB — not a shortened form.
2. A label photo if you can get one.
3. Panel type and unit: Mark V LM package, or a heavy-duty Mark V (Simplex or TMR) if that is what you operate.
4. Which IO Engine the board serves and the diagnostics you have already run.
5. Quantity, and whether this is an emergency or a planned purchase.

Logistics and terms

This DS200UCPBG6A is supplied used, cleaned and tested, with a one-year warranty as recorded in the table below. Submit the Request a Quote form with the details above; we respond within 24 hours. Shipping is worldwide DDP — duties and delivery handled to your door — and purchase orders are accepted.