Very much On Topic: Integrated Vacuum Tubes

Jim Beacon jim at
Fri Apr 22 12:42:05 CDT 2005

From: "Scott Stevens" <chenmel at>

> On Thu, 21 Apr 2005 09:31:08 -0700 (PDT)
> Tom Jennings <tomj at> wrote:
> > On Wed, 20 Apr 2005, William Donzelli wrote:
> >
> > >> - What was/is the smallest tube? purpose?
> > >
> > > RCA's Nuvistor - a family often found in late 1960s TV tuners and
> > > some test equipments. They are almost always triodes, and are really
> > > small - 3/4 inch long, maybe 3/8 inch diameter, all metal. RCA made
> > > a few half sized Nuvistors, but never sold them.
> >
> > Listers' favorite 'scopes, the Tek 5xx series, often have them in
> > the vertical plugins.
> >
> The first generation Tek 453, 'the version to avoid' has nuvistors in
> the front end.  The 453 and 454 are the last-generation Tek scope to not
> include custom unobtanium semiconductors.

I have a few 500 series plug-ins with nuvistors, and have found them to be
good reliable devices (you soon recognise the signs of a nuvistor on its way
out), I would have the nuvistor version of the 453 and 454 in preference to
the FET, but then I don't need to switch on a scope and use it immediatly.
The valve is much more tolerant of over voltage on the input.

I have seen a sub-minature valve that is about 1/4 of the size of the
nuvistor, it is a small ceramic triode, with gold pins, used in the RF stage
of radar receivers. one of my staff had a complete oscillator / mixer unit
mounted on a plinth on his desk (a present when he left the Air Force), the
unit was around 3" long and 3/8" diameter, which included the oscilator and
mixer cavities. The valve plugged in one end.


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