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We have MARK VIe system for frame 5 GT'S. What are 125V DC PDM switches & diodes in the system?
By chiranjeevi on 24 April, 2017 - 6:55 am

We have MARK VIe turbine control system,i want to have clarity on the
125V DC PDM JPDFG1A:what is the meaning of J1R, J1S, J1T, J7X, J7Y, J7Z and why diode are used at the inlet of JPDF card in MARK VIe system.

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


Well, there is an <R> processor, an <S> processor and a <T> processor. And the power supplies for the three independent and redundant control processors are (or should be) supplied by cables connected to plugs labeled and controlled by switches J2R, J1S and J1T.

The Mark VIe also has three independent and redundant protective processors, <X>, <Y> & <Z>. They are (or should be) powered by cables connected to J7X, J7Y & J7Z. I don't recall at this writing if there are switches for each of the power supplies to the protective processors, but I believe there are--but I may be (have been before) mistaken.

There should be a diagram or diagrams of typical JPDF applications in the Mark VIe System Guide, GEH-6721, usually in Vol. II. The Mark VIe System Guide is a very good place to familiarize oneself with Mark VIe hardware and how it is connected to other Mark VIe components and field devices and instruments. If the Mark VIe was an upgrade to a previous control system, there should have been a thick package of drawings provided with the control system that depict exactly how the components are connected (including the power distribution components).

It's not clear which diodes you are referring to, as there can be more than one set on the incoming power supply. But, if you're referring to the "big one" on the JPDF, it's primary function is to "choose" the higher of two possible DC inputs (usually 125 VDC) to the card.

Hope this helps!

[NOTE: The System Guide is a generic document, but it's very helpful for understanding individual components and typical interconnections to other Mark VIe components, and typical field devices. If you don't have access to a hard (printed paper) copy of GEH-6721, search the hard drive for "GEH-6721" and you should find at least one .pdf copy, if not three or more copies. Another helpful document is the ToolboxST manual (sorry; I don't recall the GE publication number. One should review all the GE publications in the HMI hard drive. One can even change the file name to add the title of the publication to make them easier to find--changing the file name does NOT affect the file's contents at all!]

By laplace1050 on 26 April, 2017 - 2:57 am

Hello !

Thank you Mr CSA for the answer.

in ToolboxST you can find also document about PDM in the PPDA.chm you will find good information about all branch card in detail.



>... and controlled by switches J2R, J1S and J1T.

should read:

"... and controlled by switches J1R, J1S and J1T."

Sorry for any confusion.

By chiranjeevi on 28 April, 2017 - 9:06 am


What difference it will create for powering protective processors for J7X, Y, Z.

Also this switches on PDM, supplying voltage to terminal boards but not to R, S, T IO packs as 28v.

Can u explain?