How the Mark V Drives Its Relay Outputs

Relay outputs are among the most frequently serviced parts of a Speedtronic Mark V, and the DS200TCRA is the board that carries them. It holds up to thirty electromechanical plug-in relays, K1 through K30, and turns the controller's commands into the contact and solenoid outputs that operate the turbine's field devices. The drive itself comes from the TCDA digital I/O board: it holds one side of each relay coil at a steady voltage and energizes the relay by sinking the opposite side to common.

That places the TCRA squarely in the Mark V digital I/O, alongside the TCDA, rather than in the <R>, <S>, <T> or <C> processor cores. A digital I/O core generally carries two TCRA boards, and their relay contacts are wired to the DTBC and DTBD terminal boards. The board holds no firmware; the choice between a dry contact and a wetted solenoid output is made by jumpers on the terminal boards, so the TCRA is a fixed-function hardware card.

The Symptom That Looks Like a TCRA but Isn't

The reason to diagnose carefully before buying is that the most common relay-output symptom — an output that will not pick up — points at several parts, only one of which is this board. Because the TCDA does the driving, a dead output can be a failed driver channel, a loose or reversed ribbon cable between TCDA and TCRA, the individual relay, or a fault out in the field.

• Look first at whether the TCDA even registers the command. If not, the cause is upstream and a relay board will not help.
• If the command is present but nothing operates, the field of suspects is the relay, the TCRA, and the ribbon; a plug-disconnected alarm isolates the ribbon.
• Then check the load. A shorted 125 VDC solenoid can burn a relay and the DTB terminal-board tracks, and it will damage a replacement board if it is not cleared first.

The pattern reported repeatedly from the field is that relays are the wear item and are usually swapped one at a time, while the board itself tends to fail only after a surge, a battery ground, or a downstream short. That distinction is what tells you whether to order a relay, a TCRA, a TCDA, or a terminal-board repair.

Matching the Group and Revision Tail

The number on this card is DS200TCRAG1A, completed by its revision as DS200TCRAG1ACC. DS200 marks the Mark V series, TCRA the relay-output function, G1 the group, and ACC the revision. GE also produced the TCRA in a group 2 form (DS200TCRAG2A); a change of group can mean a change of build, so match your panel's group and revision rather than assuming any TCRA will do, and confirm supersession if you are offered a later revision. The GE Speedtronic Part Number Decoder explains each field; read the number from the board silkscreen.

The Cards Around the Relay Board

The TCRA sits inside a well-defined group of Mark V cards: the TCDA drives it, the DTBC and DTBD terminal boards receive its outputs, the TCQA covers analog I/O, and the TCPS supplies core power. The GE Mark V DS200 Boards Explained guide describes the relationships, while the GE Mark V DS200 Boards collection shows what is on the shelf. Fleets planning ahead can read Mark V vs Mark VI: DS200 to IS200 to see how the I/O migrates to the IS200 generation.

Help Us Match Your Board Exactly

• The full DS200TCRAG1ACC part number and revision, read from the board.
• A photo of the label and silkscreen.
• Turbine model and Mark V type (Simplex or TMR).
• The core the board serves and the revisions fitted in partner cores.
• Quantity and how urgently you need the board.

Order or Request a Quote

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