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OT: Anyone have a manual for this LCR bridge?

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  • OT: Anyone have a manual for this LCR bridge?

    It is a Marconi Instruments TF868, but not a -1, nor a "B", etc, it is the first model.

    The null meter is not original, but it was last calibrated with that meter in use, so no impossible hacks are in-place.

    I found manuals for other models, with various suffixes, but not for the original type. Even found a schematic, although it is hard to read. But the calibration process is what I am after, which would be in the manual. The later versions have different circuits, and different calibration points.

    Yes it is a bit of a boat anchor, using old tube types, and having a heavy cast aluminum case, but I have it, and not a more modern unit. In fact I just collected it from a relative's estate.

    CNC machines only go through the motions

  • #2
    That looks a lot like mine (except the dial), and I think I do have the manual. I'll check when I"m out in the shop later today. Mine may be a slightly different model. But chances are I downloaded the manual rather than got it with the bridge.
    "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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    • #3
      Don't know what I was thinking - mine is not even close, it's a TF2700.
      "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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      • #4
        What is it used for?

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        • #5
          It's for measuring inductors, capacitors and if you want, resistors. LCR measurement bridge (it uses a comparison bridge circuit inside, hence the name).
          CNC machines only go through the motions

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          • #6
            That looks like a (an equivalent) circuit diagram on the top along with some instructions. Do they help any?

            What do you want to do with it? Or is it in need of repairs?

            Or parts? (Ha, ha!)

            Looks like Marconi was sold to IFR Systems which was then sold to Aeroflex and then Cobhan. Heaven only knows if they have any information but you could try.

            https://www.cobham.com/



            Originally posted by J Tiers View Post
            It is a Marconi Instruments TF868, but not a -1, nor a "B", etc, it is the first model.

            The null meter is not original, but it was last calibrated with that meter in use, so no impossible hacks are in-place.

            I found manuals for other models, with various suffixes, but not for the original type. Even found a schematic, although it is hard to read. But the calibration process is what I am after, which would be in the manual. The later versions have different circuits, and different calibration points.

            Yes it is a bit of a boat anchor, using old tube types, and having a heavy cast aluminum case, but I have it, and not a more modern unit. In fact I just collected it from a relative's estate.

            Paul A.
            SE Texas

            And if you look REAL close at an analog signal,
            You will find that it has discrete steps.

            Comment


            • #7
              Originally posted by Paul Alciatore View Post
              That looks like a (an equivalent) circuit diagram on the top along with some instructions. Do they help any?

              What do you want to do with it? Or is it in need of repairs?

              .........
              The idea is to have it work, and to calibrate it. The calibration is the main point, there are a number of adjustments, and generally the calibration process works best in a particular order of operations. I do not know that order, and there are many possible adjustment orders....... 12 things taken 12 at a time is a lot of possibilities.

              I found a somewhat illegible schematic which pretends to be the correct one. I have not found any actual glaring differences yet, but the day is yet young, as they say. The manual should give the cal procedure, but I do not have one yet.
              CNC machines only go through the motions

              Comment

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