Tube or Röhre ID, Triode, vacuum, Nuvistor and Universal shown. Radio tubes are valves. Find great deals for NOS Vacuum Tube Jan RCA Nuvistor. Shop with confidence on eBay!. The nuvistor is a type of vacuum tube announced by RCA in Most nuvistors are basically – First one released, medium mu triode; – Sharp cutoff tetrode; – triode for low plate voltages; – triode, with plate cap & grid.

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The development of the Nuvistor in the lates was probably the last major innovation in receiving valve technology, coming as it did towards the end of the era of thermionic device domination.

NOS Tube Store: RCA Nuvistor

Transistors at that time weren’t the full answer to all problems in electronics, and so valves still had a lot to offer. The Nuvistor is often regarded as a last desperate effort by valve manufacturers to stem the flow of ‘transistorisation’ which was becoming a torrent by this time. Having researched this subject I’m not sure this is true and hopefully after reading this article you’ll be able to form your own opinion. RCA announced the first Nuvistor triode valve, thein Further triodes, such as the 6CW4 which is probably the most well-known Nuvistor and a tetrode or two followed over the next few years.

In a RCA advert the company claimed:. The ‘Nuvistor’ name was intended to evoke similarities to the words ‘new’ and ‘transistor’, presumably to help overcome bias against the use of ‘old fashioned’ valve nuvisyor. In adverts and application data the word ‘Nuvistor’ was printed in a unique font, giving the impression of a Nuvistor logo, and this nhvistor be seen in the Geloso advert later on in the article.

RCA even shipped Nuvisror in a special box at least in the early days – See picture above with the Nuvistor logo on it, rather than the generic ‘RCA Electron Tube’ printed on most of their boxes. RCA coined the word ‘Nuvistorization’, this being the process of designing Nuvistors into new equipment. Nuvistors were released as triodes and tetrodes I use the plural here, which is just about valid: In Table 1 I’ve tried to summarise the significant data on all the Nuvistor types I’ve tracked down.

There may be ones I’ve missed, especially ‘special quality’ ones designed for rugged industrial applications.

I’ve added in some Russian Nuvistors, all with flying leads, but I’m sure there are many more types from this source which are not in the table. As you can see the Nuvistor is considerably smaller than the 6AF4A. Both valves have been plugged into their sockets, which don’t add too much to the overall size. I would think that the ‘HP’ valve was thus labelled for use in Hewlett-Packard test-gear but was not manufactured by Hewlett-Packard itself. Note how the valves’ part numbers are deeply stamped into the tops of the metal shells – no chance of njvistor rubbing off, which is definitely a problem with glass-enclosed valves!

A special case design was developed for these new valves, resulting in small size and very good high frequency performance, which are clearly good news for the RF stages of TV sets, but also have other useful attributes for more onerous applications. The standard nuvisyor MT4 metal shell case is shaped like an upside-down thimble, but at about 20mm high and 11mm in diameter is somewhat smaller.

The valve is made of metal and ceramic, which needed special manufacturing techniques beyond the molten glass handling and high vacuum technology more normally used for valve manufacture, which results in very low losses at high frequencies.

There is no glass envelope to be evacuated towards the end of the manufacturing process: I couldn’t find a description of exactly how the metal-ceramic seal was made. This must have been quite tricky as it had to preserve the vacuum as the valve’s case warms up and cools down in service. The tetrode case also used for some triodes has an anode cap, insulated from the metal case by a ceramic ring. The case itself is often connected to the grid of the valve, making it relatively easy to get a good ground connection in nuvistpr circuits.

Unlike in a glass-based valve there is no getter structure, whose function is to eliminate the last traces of any remaining gasses after the valve has been evacuated and sealed.

I can only conclude that the quality of the vacuum created inside the Nuvistor was very good indeed, without the need for a getter-type process step. The diagram above shows an extract from RCA’s datasheet for the 6CW4 nuvustor the physical construction and dimensions. Twelve pins hence the ‘Twelvar’ name of the base protrude through the ceramic base, some of which are ‘long’ and form the connections to the heater, cathode, grid, anode and screen grid if fitted electrodes, and some are ‘short’ and barely protrude.


These ‘short’ pins support the internal structure, along with the ‘long’ ones. See below for how these pins look on a 6CW4. The pins are integral with the internal structure of the valve, and do not have welded connections nuviator internal leads connecting to the electrodes, as is the case with most previous valve designs. These direct connections help reduce lead inductance and hence improve high frequency performance.

Two lugs ‘large’ and ‘small’ adjacent to pins 2 nuvstor 4 locate the valve in its socket, which is shown alongside. All the pins have a diameter of 0. I thought I’d open up a Nuvistor and see how closely the diagrams you can find on the Internet match reality. I ground away the metal around the circumference of the case of an RCA 6CW4 close to the base and you can see the ‘insides’ above. Mullard’s exploded view of the Nuvistor triode and its component parts.

Referring to this diagram will help identify the component parts of the 6CW4 shown above.

Nuvistor Valves

The ceramic base is about 10mm in diameter. Mullard’s diagram of the internal structure of a Nuvistor helps work out which parts of the ‘de-capped’ 6CW4 do what. All the electrodes are supported by the long and short pins. Note that there are no mica spacers used to support and separate internal structures, as in ‘normal’ valves.

Although mica is a very good insulator and capable of withstanding the high temperatures inside valves, it is brittle and can be a source of failure if the mica discs de-laminate or splinter. The tetrode grid number 1 connection is made via the metal shell, giving a solid low inductance connection to the chassis in grounded-grid amplifiers.

These views show the cylindrical electrodes very well and the supporting structure of the pins 786 directly through the ceramic base wafer. It’s interesting that the Mullard drawings seem to correspond exactly to the internals of the RCA-manufactured valve. One explanation is that RCA ‘transferred’ the design and manufacturing technology to Mullard under some mutually beneficial arrangement, nuvistoor happened with many other valve designs.

If you nuvkstor for ‘nuvistor’ on eBay, you’ll find many examples for sale, along with their photos. This is a useful resource for viewing buvistor manufacturers’ products: I think I can see some examples with squarer shoulders than others, so maybe the single manufacturer theory is incorrect. Comments nuuvistor readers who may have actually seen European Nuvistors being manufactured would be welcomed.

By the late s high frequency valve technology was nuvostor advanced and had already passed the 1GHz operating frequency point. The rationale behind using a 9-pin envelope was that this allowed five pins usually pins 1, 3, 4, 6, and 9, evenly spaced around the base, and sometimes gold plated in later versions to be used to bring out the grid connection, keeping a very short and therefore low inductance connection to ground for this critical path in grounded-grid applications. Brimar described its 6AM4 introduced in as being ‘for grounded-grid amplifier or mixer use in the frequency range to MHz’.

The valve was compact, at 37mm tall excluding pins, and nyvistor 6. The valve was also given the service code CV The B9A-based valves tended to have higher heater currents, and therefore dissipated higher power. For example the A’s heater consumed 2.

Another competing muvistor was the E88CC which in theory should have been numbered as the ECC88, but the special quality of the valve was indicated in the Mullard coding system by the numbers being presented immediately after the ‘E’ twin triode nnuvistor code CVagain in a B9A envelope, and with a 6.

7586 NOS Vacuum Tube Jan RCA Nuvistor

Mullard describe the valve as a high-slope RF pentode primarily intended for use in wideband nyvistor in telephone carrier systems, radar equipment and measuring equipment. The valve was equivalent to the and the CV Nuvistpr amateur service the EF was mainly used in the transmit, rather than the receive, path of VHF equipment. For good UHF performance the Nuvistor was designed to have low inter-electrode capacitance, especially the grid nuvistir anode capacitance; high transconductance; a high amplification factor; and a low noise factor.


The small physical size of the Nuvistor case meant that the heater power had to be kept as low as possible, but nuvistr diminutive size also meant that the cathode was small and so less power was needed to coax it to emit the electrons needed for operation. Heater power of less than 1W was achieved for most Nuvistors, and with typical anode voltages in the range V and even lower in some specialised applicationsHT power consumption could also muvistor kept low.

This low heater power implies a simpler and cheaper method of heater supply generation and less heat needed to be removed from the equipment’s enclosure. All good trends, and counter-acting to nyvistor extent the big advantage of a transistor, that is, of needing no heater power at all.

One famous audio application of the Nuvistor was in the mids Ampex MR, a costly studio-grade 1-inch 4-track tape recorder whose entire electronics section was based on triodes and push-pull pairs of tetrodes. These microphones are still very well regarded and there are restoration services available to bring them back to pristine condition. Complete power supplies, replacement capacitors, and the valves for these microphones still come up for sale on eBay occasionally.

In the nuvstor Neumann U47 studio condenser microphone, the Nuvistor was used as a replacement for the obsolete Telefunken VF valve. The VF was used in the war 75886 portable field radios, and was not manufactured after the war, and suitable valves were selected from what limited stocks still existed. This needed considerable modifications to the microphone and its accompanying power supply, which could supply up to two microphones at the same time.

This microphone was highly regarded by artists all over the world, and was used by many top recording artists such as Frank Sinatra, The Beatles, and so on. Companies still make adaptor modules for replacing the VF with a 13CW4. The U64 studio microphone was equipped with a Nuvistor from day one. The external power 75866 generated 6. This solved any obsolescence issue as the was obtainable everywhere, and could easily be replaced if necessary as it was mounted in a socket.

The rigidness of the Nuvistor structure makes these valves very resistant to microphony, and hence they don’t generate and sustain uncontrolled acoustic feedback. Along with low nuvisgor and low power this is a key reason why they have been used in microphones, and also in high-quality audio pre-amplifiers.

Its excellent VHF and UHF performance plus low noise figure made it a good choice when compared to competing valves or transistors of the day.

There’s no escaping the similarity between the word ‘Nuvistor’ and the phrase ‘New Vista’: As well as showing the electrical components in the tuner I think this view shows the mechanical complexity of the unit. Nuvistors were also found in some high quality broadcast radios. This model is still considered to nuviwtor a classic and is collected by enthusiasts today.

These all-numeric valve codes can be very misleading! When most amplifiers of the time still used valves the amplifier in this receiver was partially transistorised while still incorporating Nuvistors in the front end.

In the mids the Knight range of quality receivers and amplifiers were offered as kits nuvisstor the UK, by Electroniques.

Many professionally-built equipment for the amateur bands used Nuvistors. I’ve shown below a photo of the top chassis view of the HAA. Nuvistors, specifically the 6CW4, seem to have become commonly available in the UK in the first half of I’m not sure how prospective constructors could get hold of the special socket for their Nuvistor, so this nuvistr a challenge in itself. By the 6CW4 was priced at 1 in a magazine costing 30p, so it was considerably cheaper in real terms by then.

L2 in series with a pF capacitor forms the neutralising feedback, needed to keep the RF amplifier stable. The use of Nuvistors at this frequency, and in all the stages, seems like an indulgence, but it means that the resulting converter is neat and compact as is illustrated below. More typical amateur applications would use Nuvistkr triodes as low-noise pre-amplifiers for 70cm MHzthough A triodes in a B9A envelope, allowing the use of five pins for the critical grid connectionwere also popular at this time.