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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 10th Aug 2022, 12:02 pm   #1
djsbriscoe
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Default Nuvistor experiments-Where should I start?

I'm intrigued by the nuvistor device, and I'd like to do a few experiments just out of interest. Where should I start, and what should I avoid? Is there any practical guides I can follow. I have basic knowledge of conventional tubes through tinkering as a teenager in the 60's.
Just had a quick look on Youtube and there's not much on there. Maybe I could start with a very simple short wave radio. What are your thoughts? Thanks.
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Old 10th Aug 2022, 12:16 pm   #2
djsbriscoe
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Default Re: Nuvistor experiments-Where should I start?

Or maybe a small bench top headphone amplifier? Oops, just read that they are a bit microphonic as well as being rather expensive. Maybe not such a good idea then?

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Old 10th Aug 2022, 12:27 pm   #3
djsbriscoe
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Default Re: Nuvistor experiments-Where should I start?

Or maybe subminiature tubes are better for FM radio front ends.

https://www.effectrode.com/knowledge...niature-tubes/
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Old 10th Aug 2022, 12:53 pm   #4
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Default Re: Nuvistor experiments-Where should I start?

I think their most popular role with hobbyists was as the front end of 2m converters back in the late 60' - 70's. They were quite effective, and far less prone to the factors that killed off dual-gate mosfets, which were also popular back then.

They've also been used in some GDO's, capable of operating at higher frequencies.

B
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Old 10th Aug 2022, 1:51 pm   #5
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Default Re: Nuvistor experiments-Where should I start?

Found Nuvistors interesting also, a few years back I found that the American Mercury space missions of the 1960's used them and that hooked me!
Discovered the parallel Soviet Bloc use of their equivalents which are a bit more user friendly having flying lead termination. A socket for conventional pinned ones can be hard to find and rather costly.
The Triodes equivalent to type 7586 are available from European sellers and are type 6C51H-V (V= rugged) ISTR the Cyrillic is 6S51N-V
Differing types available inc Tetrodes with top cap connection.
Mike
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Old 10th Aug 2022, 2:21 pm   #6
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Default Re: Nuvistor experiments-Where should I start?

Cyrillic would probably look like 6C51H-B with the Latin transliteration 6S51N-V.
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Old 10th Aug 2022, 2:43 pm   #7
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Default Re: Nuvistor experiments-Where should I start?

They seem to have been a lot more popular in the US than here or in Europe. Did Philips/Mullard ever make them?
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Old 10th Aug 2022, 3:32 pm   #8
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Default Re: Nuvistor experiments-Where should I start?

I think there was an article or 2 in WW of that era, possibly with some practical circuits

Ed
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Old 10th Aug 2022, 3:52 pm   #9
djsbriscoe
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Default Re: Nuvistor experiments-Where should I start?

Looks like another search on americanradiohistory when I've got an afternoon free. Love reading the old magazines.
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Old 10th Aug 2022, 4:48 pm   #10
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Default Re: Nuvistor experiments-Where should I start?

Philips used Nuvistors in the front-end of some of their early TV cameras.
These were made by Mullard /Philips.

The ceramic bases for them might not be so easy to source.

David.
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Old 10th Aug 2022, 8:18 pm   #11
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Default Re: Nuvistor experiments-Where should I start?

In the USA, I think they were used in lots of domestic TV's.

The US military probably made some use of them, as their metal can would offer protection against EMP, and so too, their Soviet equivalents.

But in hobbyist terms, (leaving out 2m converters) I think I've seen saw more articles about Acorn valves (c1930's) than Nuvistors.

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Old 10th Aug 2022, 8:21 pm   #12
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Default Re: Nuvistor experiments-Where should I start?

Hi Folks, don't forget FETRONS

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Old 10th Aug 2022, 9:11 pm   #13
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Default Re: Nuvistor experiments-Where should I start?

I have a few circuits from Radio Televison and Hobbies magazine that uses them, but I have never been able to find any. They were used in a distortion analyser as the first stage of the meter amplifier,. The other design was for a very low distortion oscillator ( audio ) in the precision attenuator.

Both projects received high marks for their accuaracy.

Joe
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Old 11th Aug 2022, 12:51 pm   #14
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Default Re: Nuvistor experiments-Where should I start?

I had an rms valve voltmeter containing a couple. I beleive it was a Solatron.
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Old 11th Aug 2022, 1:37 pm   #15
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Default Re: Nuvistor experiments-Where should I start?

"Where should I start?"

Where do you want to go? What do you want to achieve?

Nuvistors were developed to improve on the performance of typical small RF valves of the period.

RCA's datasheet for the 6CW4 proclaims it as good for VHF TV and radio tuners, and suggests grounded grid operation to remove the need for neutralisation.

This was looking at the world through American-coloured glasses, their TV was VHF and destined to stay so for quite some time.

The nuvistor was small which reduced stray C, but more importantly the lengths between electrodes and their pins were short, reducing stray inductance. This is the real killer at RF and still is with many transistors.

The Nuvistor caught on a bit in the US, but its cost was really too high to take over the market. In Europe, it got no traction. Some European all-glass valves outdid it and cost ordinary all-glass sorts of prices. This was done by European valve manufacturers making stumpy little valves for VHF and UFH tuners, with a secret weapon: Multiple cathode pins!

So the Nuvistor eventually fizzled. Clever all glass valves got to outperform them in the mass market tasks, and undercut them significantly on price.

Nuvistors got used in some scopes and instruments because they were small, but it wasn't too long before transistors came along good enough to steal their lunch.

So you don't need to experiment with Nuvistors, you could have a play with European UHF TV tuner types. You can find these more easily and even find sockets.

Nuvistors had something to offer, but they only had a small window to do it in.

The hifi world might like them because they seem exotic and are reassuringly expensive, both the valve and the socket, and quite hard to get.

In the UK there was a 2-metre receive converter designed around one as the RF input amplifier stage. It was published in Radcom at some time in the early sixties, but it's more easily found in the mid sixties and early seventies editions of the RSGB handbook. There were a few other, similar designs in other periodicals, but you could do better with some true exotica like disc-seal triodes and 'lighthouse triodes' GEC made some special low noise valves as well. None of these are easy to find nowadays. I'd suggest the UHF telly valves as a better choice.

The one thing the nuvistor was unchallenged on by other valves was smallness, but before long it got bluto'd in that respect by transistors.

David
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Old 11th Aug 2022, 2:01 pm   #16
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Default Re: Nuvistor experiments-Where should I start?

They're used in several Tek 500 series scope plugins for the vertical amplifier function,they're essentially AFAIK LV triodes.

They were used in several hifi amps see - http://www.r-type.org/articles/art-150.htm and Ampex used them in their R2R's. Also used in Nueman mics.

Andy.
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Old 11th Aug 2022, 3:46 pm   #17
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Default Re: Nuvistor experiments-Where should I start?

Those were applications which needed their small size in the professional gear. Domestic hifi would have chosen them as exotica.

"Anode supply rating" == HT: 100 volts.

David
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Old 11th Aug 2022, 4:00 pm   #18
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Default Re: Nuvistor experiments-Where should I start?

Somewhere I have a circuit for a 2-Metre walkie talkie using a Nuvistor that is switched between working as a superregen receiver and a self excited oscillator. Shades of the WS19 'B'-set... There was apparently a design for a 70cm superregen using Nuvistor as RF amp and detector in one of the ARRL handbooks in the early 60s.

But their biggest claim to fame is being used in RCA 'New Vista' color tellies.
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Old 11th Aug 2022, 4:48 pm   #19
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Default Re: Nuvistor experiments-Where should I start?

Well, the thread seems to be running rather cool on the suject.... but here's one that I did make earlier, sometime around 1970, my 2m pre-amp using two 6CW4's!

Looks rather tarnished now, but certainly provided some gain, but I did not have the expertise or the equipment to optimise the S/N ratio.

B
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Old 11th Aug 2022, 5:59 pm   #20
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Default Re: Nuvistor experiments-Where should I start?

I came across nuvistors first in a Telequipment S54. Later I found them in Dynamo 7100 (?) series scopes, plus of course in a few Tek scopes.
I had a TQ S54 with very low emission output nuvistors, and had no spares (13SD4 I think, 12v filaments) so I played around trying to get FETs to work, along the lines of the later model S54A. If I recall, I had a zener (70 or so volts) in the anode circuits and got them working in both Y amp and timebase.
Later I tried to do the same to a Dynamco, but failed miserably, so back to stock nuvistors.
Now if David (RW) things they could be used in EXPENSIVE amps, bring it on. I have maybe a dozen tucked away, all tested (VCM-4).
If there were more hours in the day, maybe a 1 or 2 valve radio along the lines of the one I built (from a kit) in about 1955.
Perhaps those EXPENSIVE amps could find a use for TUNNEL diodes. I have a stash of those new little gold devices also tucked away.
Les.
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