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Wheelspace Thermocouple
Wheelspace Thermocouple showing -17 degree Celsius after the unit shut down on gas limitation.

Good day,

We are running GE frame 6 gas turbine unit with speedtronic Mark VI turbine controller. about two days ago when we have short supply of gas from our supplier, a unit has to be shut down, So some hours after that, when the unit operator was checking the status of the machine, he found out that all wheel space thermocouple in the unit shows -17 degree Celsius.

please can anybody tell me what might the problem and possible solution to it.


Dear control guy

1st thing you should check the analog card of those thermocouples in MKVI panel. the 2nd thing is checking the comm plugs and data cable of these T.C's between the terminal card and analog card on the MKVI rack.

please feedback me

1 out of 1 members thought this post was helpful...


It's common practice for all of the wheelspace T/Cs to be connected to a single TBTC terminal board, and that terminal board is then connected to a VTCC card in one of the Mark VI processor racks (I presume the Mark VI is TMR, but it might be SIMPLEX...). If that VTCC or TBTC is having issues there should be Diagnostic Alarms present when checking the card status using Toolbox (or ToolboxST, as the case may be these days).

There are also large "black" (to some people) or brown (to others) cables with 37-pin connectors on each end that connect the TBTC to the VTCC. There should be labels attached to the cables that indicate where the other end of the cable is connected. Start at the TBTC end and make sure the connector is properly plugged into the connector on the TBTC card, and that the clips on the connector are properly positioned.

Be aware that if you unplug the cable when there is power to the Mark VI processor rack the TBTC is connected to that if you don't plug it back in exactly correctly that pins in the cable connector can short against the plug on the TBTC card and damage the VTCC! So, it's recommended that the Mark VI processor which connects to the TBTC card with the wheelspace T/Cs be powered down when checking the cables!

Once you're certain the TBTC ends of the interconnecting cables are properly and fully inserted and the clips are properly positioned (to hold the connectors in place), go to the other end of the cables and make sure they are properly connected, also, and that the clips are properly positioned (to hold the connectors in place).

Resolve any other Diagnostic Alarms that may be present; for, example, there might be a problem with the Mark VI rack-mounted power supply which is affecting the VTCC card.

Please write back to let us know what you find!

Hi Danny,

Following your message, I want to know:
How many wheelspace thermocouples installed?

What is the status and values of all wheelspace thermocouples during Gt running, before shutdown?

If all thermocouples are good and their measures values are normal. Then the problem is only the cards. Try to remove the power supply for the controller and then you will see the difference after power supply on.

Waiting your feedback.


Twelve wheelspace thermocouple were installed. I will try to check their values when running, but the status of others were okay while running.