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Help with vintage Tek scope

Discussion in 'Electronic Equipment' started by Stuff, Mar 16, 2005.

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  1. Stuff

    Stuff Guest

    I'm wondering if someone out there knows the type of coax used in the
    500-series extender #013-055... I'm guessing by looking at the driver
    circuitry it would ideally drive 93 ohm coax, but the (totally
    unmarked) coax used in the extender has the following dimensions:
    conductor: 15 mils , stranded
    dielectric: 95 mils dia, white, seems to resist heat quite well, but
    not as well as teflon
    total outer dia: 140 mils

    The only 93 ohm coax I've dug up is RG-62/AU, which has a thick solid
    conductor and is way stiffer and larger than the coax used in the
    extender. I can't seem to match this coax to anything I know by the
    dimensions alone, and I don't know the impedance I need for sure.
    I'm guessing also the coax has a very low pF/ft rating to help those
    tube drivers out a bit.
  2. Jim Adney

    Jim Adney Guest

    I don't have the specs here, but that sounds like RG-174, which is
    just 50 Ohm.
    The RG-62 is low C and 93 Ohm, and might even be better for your
    extender. Is there room for it?

    The plugin probably doesn't have its full bandwidth with the extender
    installed, and an extender with the 6 digit part number would have
    been an early one, which might have been made with one of the earlier
    500 series (lower bandwidth) scopes in mind. I don't know, but it's
    possible that tek changed the cable in later versions.

  3. Stuff

    Stuff Guest

    The RG-174 I have here is the wrong dimensions, for one thing, the
    ratio of inner/outer diameter is different, and is smaller. It's dirt
    cheap, it melts very easily. ie, I think it's crap...
    Oh sure, but the stiff nature of the 62 makes me worry that at some
    point, the cable will destroy the metal tabs on the blue ribbon
    connectors I have. The 62 has a steel copper covered conductor which
    is strong enough to break the tab in two.
    I never thought of that. The extender came with the 547, which both
    came from a tech of Radio-Canada, I always assumed they went together.
    Certainly I never noticed any large differences when using it.

    I am trying to make a long extender so I can work on plug-ins more
    freely. The plug-in I want to fix is a TDR plug-in, which I would use
    to find the impedance of the cable... Oh well.

    I'm still waiting for my Teflon #22 wire to come in to build the
    extender, so I have time to find the type of coax.
  4. Steven Swift

    Steven Swift Guest

    Tek made a lot of custom coax in those old days to get the exact delay
    characteristics they wanted. It was one of their "trade secrets" that made
    them lots of money. It is also why their probes were always better.

    So, don't be surprised if you can't find a match.

  5. Jim Yanik

    Jim Yanik Guest

    (Steven Swift) wrote in
    AFAIK,TEK never made their own coax.
    Perhaps they special-ordered some from cable manufacturers.
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