Nuvistor Tubes in Radios-History+Applications for Nuvistors

Nuvistor Tubes in Radios – History and Applications for Nuvistors

The market for nuvistor tubes is not the radio but other technical applications for instance for measuring instruments, military equipment etc. But nuvistors can also be found in TVs and very seldom also in radios for public broadcast.

There are also other rare uses like for instance the replacement of the tube VF14 by using a nuvistor 13CW4 (RCA) in the microphones Neumann/Telefunken U47 and U48. Naturally some changes in the cirquit are necessary. The 13CW4 was used in many logging tools for two decades. It is a high mu triode with 13.5 volt, .06 amp filaments, and a maximum plate rating of 1.5 watts and 135 volts.

Still, since the Nuvistor was developed and introduced by RCA in 1959 it had a short life because of the upcoming of the transistor. It was one of the last major advances in basic vacuum tube technology. Nuvistors were initially very attractive because they handled momentary overloads better than transistors and they could handle also higher impedance devices than the transistors of 1959. But at the same time the market saw the introduction of the first integrated circuit based on solid state technology.

Nevertheless, by April of 1959, RCA already demonstrated the use of Nuvistors in TV tuners, which reduced the volume to one third of the conventional tuners of the day.

The Nuvistor was sometimes smaller than the transistors of 1959 and in some cases even cheaper. Many Nuvistors were used in TV tuners in the 1960's. The other field was the use in military and industrial equipment since FETs were not yet commercially available. High impedance input stages and high frequency, high gain was the “power” of those tubes with low noise up into the VHF and UHF frequency.

The first Nuvistor type was published in “Electronic Design” in 15th April 1959 as 6CW4. Like most of the Nuvistors, the 6CW4 is a triode. There are also a few Nuvistor tetrodes. Philips/Mullard followed with the 7568. The Nuvistor is a real ceramic tube without glass, made in a vacuumized surrounding for not having to pump out and seal a tube. This is the main difference including an automatic process from A to Z.

In this article we will show a few examples of radios with Nuvistors and some other examples with Nuvistors – either hybrids with also solid state technique or models with tubes only. I’m sure some members will show us also some technical details of solutions with a Nuvistor or many Nuvistors.

In our forum for German language Bernhard Nagel showed some details about the Braun CE1000/2 which uses 2 Nuvistor 6CW4 in the FM tuner. He could use the pictures here too.

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We have listed quite a lot of Nuvistors in our pages for tubes. You can just go to the tab "Tubes" and then enter the field for tube search with the name of a Nuvistor and you will probably find data needed. We still lack some data sheets but this will be provided by request.

If you want to find all Nuvistors together as a list you use the "Search for Tubes by Criteria".

In the first step you select "Base". In the second you select "Nuvistor" after scrolling down a bit.

At the moment you get 41 different Nuvistors and then can select a Nuvistor to get it's data. At the same time you can overlook in the Nuvistor list the number of models within Radiomuseum.org (RMorg) using a particular Nuvistor - some of them carrying also schematics. You can for instance click the Nuvistor 7586 and you find photos of this particular Nuvistor, base pictures, typical application schematic plus data sheets - and you can click some models there below which carry such a Nuvistor 7586. The same information you find for the Nuvistor 7587 and for many more.

The most often used Nuvistor in our list is at the moment the 6CW4 with 30 different models, followed by the Nuvistors 7586 (15 models) and 6DS4 plus 13CW4 (5 models each).

 

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I will delete my post here after somebody has added good content to this article.
There is still much to say to Nuvistors and its applications.

Who can bring in models like Radio Repair Equipment, radios or TV's with Nuvistor tubes? 

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Yes, nuvistors appeared on the scene too late to compete with semiconductor devices and their extensive use to replace standard tubes was not justified by the few benefits claimed over them. In the late fifties the vacuum tube industry had reached its apex, with an incredible variety of reliable devices, based upon almost any known principles and on the most advanced technologies. Nuvistor was just a simple signal amplifier, something smaller, yet considerably more expensive than a 6C4: it could never replace the variety of miniature and subminiature tubes already in production. On the other side, lots of reliable solid state devices were replacing tubes in many and many circuits. Day after day their performances, frequency range and power increased, while prices went down: tunnel diodes operated in the gigahertz region, but even transistors, such as germanium micro-diffused alloy or silicon mesa types, were going up to several hundreds megahertz and gigahertz.

Roughly after 1965 vacuum tubes still survived just in specialty niches, such as very high power or microwave applications. Nuvistors were soon forgotten.

Nevertheless RCA promoted nuvistors in every possible application where space was a premium and some critical performances were still to come from the semiconductor market. Here the pictures of a nuvistor promo kit, also including some developmental types, the ones with white labels, identified by their internal laboratory design figure, A15133, followed by a serial number.

forumdata/users/6435/nuvistor/RCA_Nuvistor_promo_a.jpg
forumdata/users/6435/nuvistor/RCA_Nuvistor_promo_b.jpg

Close-up view of a A15133 nuvistor prototype. No data available.

forumdata/users/6435/nuvistor/RCA_A15133.jpg

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