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 Post subject: NUVISTOR INFO
PostPosted: Feb Fri 15, 2019 10:01 pm 
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Location: Bloomsburg PA 17815
I'm curious about nuvistors and what equipment they were used in. My career in TV broadcasting started at the beginning of the transistor era. If I encountered nuvistors it has long left my memory. I know they were basically a "last gasp" attempt from tube manufacturers to try to compete with the miniaturization that transistors introduced. From what I've read they were mostly triodes and a few pentodes. Apparently had some excellent characteristics for VHF & UHF but it seems to me they were very costly to manufacture compared to transistors.
They seemed better suited for precision devices like O-scopes but could not compete with transistors in the long run. They did seem to be reliable.
I did very little work on TV receivers but I may have encountered them in UHF tuners.
Does anyone encounter them very often now?


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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Fri 15, 2019 11:15 pm 
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Location: Colorado Springs, Colorado
I have some 700 series Fairchild / Dumont oscilloscope plug in's that use several Nuvistors.
The vertical plug in's use them, all triodes, to achieve high input impedance. The time base
plug in's use them in the trigger input, triodes, for high impedance and also in the
miller integrator sweep circuit, one triode and one tetrode, for high impedance reasons also.
The remainder of the circuits are all transistor. So yes I encounter them quite often but those
are not my main use oscilloscopes any more.

HP used one in their old 215A pulse generator.

I have see a few TV sets with one in it's tuner section.

That is the extent of my first hand experience with Nuvistors. I have read that they were
used in some TEK oscilloscopes. Also in some microphone preamps and as preamps in some
audio gear.

I am pretty sure there were no pentode Nuvistors. Just triodes and tetrodes.

Bob


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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 12:27 am 
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They were used in a number of amateur radio receivers and transceivers throughout the 60's. Also used in at least one or two high-end microphones and TV tuners.

Types
7586 - First one released, medium mu triode
7587 - Sharp cutoff tetrode
8056 - triode for low plate voltages
8058 - triode, with plate cap & grid on shell, for UHF performance
7895 - 7586 with higher mu
2CW4 - Same as type 6CW4, but with a 2.1 volt / 450 milliampere heater. Used in television receivers with series heater strings
6CW4 - high mu triode, most common one in consumer electronics
6DS4 - remote cutoff 6CW4
6DV4 - medium mu, intended as UHF oscillator, shell sometimes gold plated
8393 - medium mu, used in Tektronix scopes (12.6 volt filament)
13CW4 - same as 6CW4, but with 12.6 Volt / 230 milliampere heater

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 12:29 am 
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I've got a couple of Lafayette TE-57 grid dip meters that each use a 6CW4 nuvistor for the oscillator tube.

Jeff


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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 2:20 am 
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Nuvistors came out in the beginning of the 60's as far as I can determine. In TVs they mostly showed up near the end of the 60's, that may be why people think of them as a "last gasp". Compactrons came out in the late 60's, so they were as much a last gasp as anything.

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 2:52 am 
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Yea, some modern hi fi manufacturers have tried them in preamps and I think, maybe the analog stage of a CD player. No idea of what the idea was unless they have low microphonics besides the built in shielding. I know at least one very expensive studio microphone used a nuvistor in it. When they first came out, some ham gear used them in the front end RF amps and mixers due to the low noise for VHF UHF. Before that the VHF tubes with the lowest noise figures were miniature types that were apparently hard to get, expensive, and very fragile. Some WE 400 series tubes, not acorns. I had an AMECO VHF converter once that used them. Never got it to work all that well. AMECO also made shortwave preselectors that used a nuvistor, but when mosfets came along they switched right away.


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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 5:35 am 
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AFAIK size had little to do with the original intent of the Nuvistor. Designed in '59 by RCA, the first was 6CW4 regestered July '60 as TV tuner RF amp(and used as such in 1961 models). Gave better S/N ratio than conventional tubes, awarded 1961's best tube. The first industrial application was the general usage/UHF 7586, regestered a couple weeks after 6CW4.

Info gleaned from Lud Sibley's Tube Lore.

Notimetolooz wrote:
Nuvistors came out in the beginning of the 60's as far as I can determine. In TVs they mostly showed up near the end of the 60's, that may be why people think of them as a "last gasp". Compactrons came out in the late 60's, so they were as much a last gasp as anything.

First Compactron was 6AX3, 6B10, 6FJ7 all regestered by GE 1/2/61, with others soon to follow. By end of '60s were in their twilight years.

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 5:53 am 
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It was my impression that Nuvistors were a step forward, and the size was part of why they were better, not an attempt at competing with transistors.

Maybe the idea came early, but it took a while to get into production.

They were really good at VHF/UHF. I've seen a review of an early Nuvistor converter, and he compares it with one with a 417 tube, and realizes his really good converter needs a tune up. Apparently the Nuvistor was less finicky, so while the 417 and 416 (which were expensive) could be better, the Nuvistor gave good results without as much tuning.

It was a small window where the Nuvistor was great. A few years later and there were jfets which were better, and maybe a decade later bipolar transistors that were better still.

But you design with things you have, the Nuvistor was there, so in it went, into various products. The size didn't matter, but for VHF/UHF you wanted short leads, and Nuvistors allowed for that. Once they were available, why not take advantage of their small size?

As someone pointed out, there was one that could run on 12volt plate, which happened around then for miniature tubes, and maybe was a reaction to transistors.

Note that list is fairly limited, they did come too late to make general inroads before solid state took over.

Michael


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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 9:41 am 
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As front end VHF/UHF RF amp and mixer tubes, with their high gain and low noise level, made them very good tubes to use.
The WECo 417A triode had an extremely low noise and high gain for RF amp and mixers but input and output sections of the tube socket sometimes required a small shield and/or some TLC in order to keep the tube from going into oscillation.
If you had or built a W2AZL 2 meter receiving converter back in 1959, you had some good stuff. I think one of the first consumer had ads for the nuvistor appeared on a read cover QST in 1959(? from memory) I think I might still have two or three of these AZL converters floating around. I have good stock on various nuvistors since my Clegg Interceptor receivers use 4 or 5 of them each plus I like to acquire VHF rigs at flea markets that may also use them. My 417A stock is also good for these AZL converters and a few other home built projects that use them.

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 12:36 pm 
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I have some old ARC private aircraft avionics stashed. They used both a bunch of nuvistors and also compactrons. I have both NOS and salvaged nuvistors and a very few of the special sockets, which sell for a hefty price on ebay. I have to admit I don't recall actually making or doing anything with them, except a few occasions to encounter them such as the AMECO converters. JFETS and MOSFETS positively buried them for their intended purposes. Low noise bipolar transistors also beat them for noise but have problems that leave the FETS ahead.


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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 3:32 pm 
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BobVB wrote:
I have read that they were used in some TEK oscilloscopes.

They were used in the first laboratory grade 'scope designed for transportation.

In the mid-'60s IBM wanted a 'scope that was easily transportable and met the needs of their field technicians. For IBM mainframe service IBM needed a laboratory grade 50 MHz dual trace 'scope with full features including delayed triggered sweep. It also needed to fit under an airplane seat. Tek developed the 453 for IBM and introduced it in 1965. The initial production (serials below 20,000) used nine vacuum tubes. In addition to the CRT and two 5642 pencil rectifiers in the CRT HV supply the 453 used six 8393 Nuvistors. Each channel had one 8393 in the input, one in the sweep generator, and one in the trigger generator. At the time Nuvistors offered better gain-bandwith product and higher input impedance than generally available in solid state. The 453 had another innovation - the first lockable dual-tilt bail handle in instrumentation.

Two years later, in 1967, Tek introduced the first revision of the 453 in serials 20,000 and above. It still had the CRT and the pencil rectifiers, but the six 8393 Nuvistors had been replaced by FETs.

Many 453s in the wild have the IBM logo factory stenciled on the front panel. Mine (serial above 20,000) does - it came out of the Charlotte NC IBM service facility. IIRC IBM was still using the 453 in the field as late as the late '80s. I worked for an employer who has an IBM mini in the late '80s and I think the tech used a 453.

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Last edited by Dale H. Cook on Feb Sat 16, 2019 7:19 pm, edited 1 time in total.

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 5:38 pm 
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I thank everyone for their response. More information than I could find on the web AND exactly what I wanted to satisfy my curiosity.


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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 6:28 pm 
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Dont forget the 2EG4 triode nuvistor.

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sat 16, 2019 8:35 pm 
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wazz wrote:
I have some old ARC private aircraft avionics stashed. They used both a bunch of nuvistors and also compactrons. I have both NOS and salvaged nuvistors and a very few of the special sockets, which sell for a hefty price on ebay. I have to admit I don't recall actually making or doing anything with them, except a few occasions to encounter them such as the AMECO converters. JFETS and MOSFETS positively buried them for their intended purposes. Low noise bipolar transistors also beat them for noise but have problems that leave the FETS ahead.

Back in the early days, I found that the nuvistors were much better on strong RF signals keeping signals from going into front-end overload over the early FETs and bipolar transistors. By the 70's, the FETS and some bipolars had taken command over front-end RF design in many circuits.

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sun 17, 2019 4:15 am 
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As mentioned RCA used 6CW4 Nuvistors in their VHF tuners in the mid to late 60s.
I've encountered a few of them in my time.

The Polytronics Poly-Comm 2m and 6m AM transceivers use them as well.

The 2M model has FIVE Nuvistors!

-Steve

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Sun 17, 2019 8:50 am 
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If ya got nothing better to do, here's an article on building a 2 meter transceiver using transistors and six nuvistors:
Part 1: http://n4trb.com/AmateurRadio/RCA_Ham_T ... ps2502.pdf
Part 2: http://n4trb.com/AmateurRadio/RCA_Ham_T ... ps2503.pdf

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Mon 18, 2019 5:34 am 
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The Fisher 600T receiver and probably other Fishers in that era had two nuvistors and one 7pin miniature in the tuner. The rest of the unit is all solid state.

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Mon 18, 2019 12:43 pm 
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Not to belabor the point but HH Scott used thr Nuvistor in some of its tuners as well. If memory serves me well, the early transistor tuners used them in the front end.

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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Mon 18, 2019 4:59 pm 
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Here is a list of the American nuvistors. I might be missing one or two 8000 series types.
2CW4, 2DS4, 2DV4, 2EG4, 6CW4, 6DS4, 6DV4, 13CW4, 7586, 7587, 7895, 8056, 8058, 8203, 8380, 8393, 8627, 8628, 8808

These are Japanese nuvistors made by Hitachi sometimes found in the USA boxed for Raytheon. This list is probably not complete
2B-H5, 2N-H11, 2N-H12, 7N-R30

Jim Cross


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 Post subject: Re: NUVISTOR INFO
PostPosted: Feb Tue 19, 2019 5:52 am 
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Ok, I think this is the rest of the set.

8382, 8392, 8398, 8441, 8456


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