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Some one who know how we can see DOS_OnLine of LVDT (Nozzle) under Mk6?
1 out of 1 members thought this post was helpful...

Some one who know how we can see DOS_OnLine of LVDT (Nozzle) under Mk6. I heared about TELNET SESSION!. What was the details and how it work?

Thank you.

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


It would be easier if you told us what problem(s) you are experiencing, and what troubleshooting you have done to try to resolve the problem(s), and what the results of your troubleshooting were.

Using Telnet and TSM (for Mark VI; llm (Low Level Monitor) for Mark VIe) are best done with the assistance of GE as they are the ones who know the codes and commands and can help to obtain data that they are best at analyzing.

The majority of problems (real or perceived) can be analyzed and resolved using Toolbox (or ToolboxST, depending on the HMI and version of Mark VI). We can help with that--if you can tell us what problems you are experiencing, what you've done to try to resolve the problems and what the results were. Using TSM or llm can be very dangerous when the unit is running if not used correctly because one is dealing directly with the RAM (Random Access Memory) on the VSVO (or the PSVO for Mark VIe). Both of these programs can change values in RAM which would NOT be good for a running turbine.

Tell us what you are trying to resolve or analyze, and we can probably tell you how to use Toolbox or ToolboxST to help. I think someone in the past has offered a "cheat sheet" for either TSM or llm; you can use the 'Search' feature of to search for "+Telnet" (without the quotes) and see if you can find the individual's email address to ask for a copy. That individual seems to lurk on, and doesn't post very often, but he may see this post and reply with an offer.

In my personal opinion, TSM or llm should only be used under the guidance and direction of GE as they are the only ones who know the commands and the pitfalls and are in the best position to analyze the data which can be retrieved using TSM or llm. These are two of those things should "never be tried at home."

So, take some time and compose a reply with the problem(s) you are experiencing, what you've done to try to troubleshoot the problem, and what the results of your efforts were. DO NOT forget to include any Process Alarms >>AND<< Diagnostic Alarms which are being annunciated when you are experiencing these problem(s). Also, please tell us what machine you are working on (Frame 5002D; Frame 6B; Frame 5001P; Frame 9FA; etc.). The more information you can provide, the more concise our reply can be--and that will save us both a lot of time and back-and-forth.

We look forward to your complete reply!

2 out of 2 members thought this post was helpful...


I want to add a couple of things about LVDTs. There are highly reliable devices. They have no moving parts (yes; the core moves in and out of the armature along with the valve stem or device being monitored). They have no friction--when installed and maintained correctly. They don't drift like many electronic devices. They are used on many aircraft (commercial) and rocket engines because they are reliable, don't drift, and can withstand high temperatures.

When one is using AutoCalibrate one is calibrating (scaling) LVDT feedback--and NOTHING else. AutoCalibrate does nothing to the electrohydraulic servo-valve ("servo") or the hydraulic actuator. It ONLY calibrates (scales) LVDT feedback. Full stop. Period. Autocalibrate can be used to help with diagnosing problems with servos and actuators, and even LVDTs.

But, in general, LVDTs rarely go out of "calibration" because they don't drift. Even on GE gas valves, particularly the combined Stop/Ratio- and Gas Control Valve assemblies. The combined gas valve assemblies are constructed differently from most other valves, and that difference needs to be factored into account when calibrating LVDT feedback from those valves. (That topic has been covered MANY times before on, and ALL of those past threads can be found using the 'Search' feature of NOTE: The context of the search terms for's 'Search' feature are unlike most World Wide Web search engines; refer to the Search 'Help' for guidance.)

Improperly installed or improperly maintained LVDTs can have metal-to-metal contact which can eventually damage the armature windings and lead to intermittent feedback issues and even failure of the LVDT. Improperly installed LVDTs--those which do not have their "zero-stroke" voltage settings properly adjusted--can also cause intermittent problems. A TRUE AC RMS voltmeter--one that can measure AC voltages of less than 1.0 VAC RMS at 3000 Hz (3 KHz) are necessary when adjusting the zero stroke voltage setting of the LVDT. (Alternatively, one can view the LVDT feedback voltage using Toolbox or ToolboxST when setting the LVDT zero stroke voltage setting.)

LVDTs and servo-valves as used on GE-design heavy duty gas turbines have a lot of false and misleading information associated with them. Again, if you can provide more information we can probably be of help. You may have heard of someone using Telnet/TSM/llm to get some information--but I'm fairly confident it was done with the guidance of someone from GE. And, I'm also fairly confident the root cause of whatever problem was being investigated was fairly benign and could have been solved without using Telnet/TSM/llm, but it was probably faster to get actionable data using Telnet/TSM/llm so that's what was used.