Help with vintage Tek scope

[Stuff]

Hi,
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.
Thanks!

 

[Jim Adney]

On 15 Mar 2005 20:18:09 -0800 a7yvm109gf5d1@netzero.com (Stuff) wrote:

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

I don't have the specs here, but that sounds like RG-174, which is
just 50 Ohm.

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.

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.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Stuff]

Jim Adney <jadney@vwtype3.org> wrote in message news:<ps1i31pqdo6a60eoq4kprrnoi0imt2h9dk@4ax.com>...

I don't have the specs here, but that sounds like RG-174, which is
just 50 Ohm.

Hi,

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...

The RG-62 is low C and 93 Ohm, and might even be better for your
extender. Is there room for it?

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.

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.

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.

 

[Steven Swift]

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.

Steve.

--
Steven D. Swift, novatech@eskimo.com, http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA

 

[Jim Yanik]

novatech@eskimo.com (Steven Swift) wrote in
news:d2aepm$v68$1@eskinews.eskimo.com:

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.

Steve.

AFAIK,TEK never made their own coax.
Perhaps they special-ordered some from cable manufacturers.

--
Jim Yanik
jyanik
at
kua.net