Nude EF50's Look Great

[ms660]

The RCA metal envelope valves/tubes:

http://www.rfcafe.com/references/rad...adio-craft.htm

http://www.r-type.org/articles/art-018.htm

Lawrence.

[G6Tanuki]

Noticing mention of the Catkins in the article above, I gather that there was a HT-rectifier version of the "Catkin". Aieeee!!!

I really hope that the perforated-metal screen was well-attached, otherwise you could touch the rectifier anodes!

[Cobaltblue]

Don't remember seeing a rectifier but there was certainly an output pentode MPT4 Catkin and that had no screening can the Anode was totally exposed

http://www.r-type.org/exhib/aab0043.htm

these are a bit lethal I somewhere have a set with a set of Catkins I haven't come across it yet but I still have more than 100 sets to unpack

Cheers

Mike T

[Argus25]

I think the EF50 has great historical significance to the UK. They are a limited resource to be preserved where possible. They outclassed their American contemporary , the 6AC7 which was a plain octal, and not as suited to Airborne use like a local. As pointed out, they supported the radio and Radar gear that won the war.
If these did get widespread audio use, eventually all the originals (of which there might seem plenty now) will get used up, then they get cloned but the clones will never be as good,not for RF applications anyway.

When I first saw the EF50, over 50 years ago, I was "blown away" and my opinion of them and their significance in valve history has not changed since. It was one of the things that inspired me to build the Argus TV set.

[Ed_Dinning]

Hi Gents, there was a 3, EF50 set in an edition of PW back in the 50's/60's.

Ed

[M0FYA Andy]

I've posted these pictures before, but they seem relevant again.
This is an EF50 in my collection with a brass screening can, not the usual aluminium.
I've never seen another one, and despite asking around for any opinions on 'why, when, who', nobody else has come up with any suggestions, so it remains a mystery oddity.

[Radio Wrangler]

This is part of a general problem. The audio business, driven by the twin principles that valves are best and only NOS are any good. will work its way through all period thermionic devices in existence that are capable of amplification or rectification.

As stocks of their preferred types get used up, prices will soar and people without bottomless pockets will go looking for any alternatives. There have been people looking for cheaper alternatives for a long time.

New valves are in current production, but these are exclusively audio/guitar/rectifier types. That's where tho money is, but it's a dramatic reduction from the number of types of the past. If your interest is in radio or TV, you're left out in the cold.

I have a few valve radios for which I've bought spares, and I have a small collection of valves from my teenage exploits, but that's it. On a matter of principle, I design no new equipment around valves. I'd rather leave period devices to keep period equipment going. This isn't an onerous limitation, because I allow myself to listen to music through transistors, and I even allow myself to enjoy it. Over the years I've fixed numerous Quad IIs and Leaks for people and I like the engineering in them, but I don't have one. I don't really need one.

I remember de-canning a dead EF50 back in the sixties, admiring its ellegance and discovering that the evacuation pip is hidden in the spigot of the base... neat!

David

[G6Tanuki]

Originally Posted by Ed_Dinning

Hi Gents, there was a 3, EF50 set in an edition of PW back in the 50's/60's.

Ed

There have been quite a few such published over the years.... including one where an EF50 was used as the power(?)-output stage!

Using 'Wearite' coils, an EF50 RF amp followed by an EF50 infinite-impedance-detector was at one time the basis of my 'high quality local-station' medium-wave tuner, fixed-tuned to 247M Radio-1 and fed from a 60-foot-or-so longwire antenna. The lack of AGC to cope with fading was a nuisance as daytime moved into nighttime.

[Bob_Moss]

Originally Posted by Argus25

Whatever you do don't encourage the use of the EF50 in audio applications. They are not suited to it and have extremely high micrphonics. Already I have seen some stuffed into PVC tubes with latex rubber to damp them down.

Please, please, please, convince the audiophiles that that the route to Nirvana lies with the EF80! If these increase in price then I'm minted!

[Cobaltblue]

Originally Posted by Bob_Moss

Please, please, please, convince the audiophiles that the route to Nirvana lies with the EF80! If these increase in price then I'm minted!

Yes many of us would be

Cheers

Mike T

[turretslug]

Apparently, there were even a handful of mid '40s consumer radios that used the EF50 as an RF stage;

http://www.bushradio.co.uk/bushexport.html

which seems a little odd- something like the EF39 would seem more appropriate from various angles- variable-mu as opposed to straight, the same International Octal valve socket as other valves on the same chassis, easing stock-holding and chassis-punching. Perhaps by this time EF50s were so plentiful as surplus that there was an element of "too cheap to resist" by some designers. Marconi's CR150 used a quad of EF50s in its front end with scaled AGC for the two RF amps, but that's understandable in a set that endeavoured to cover up to 60MHz, less easy to rationalise in a domestic-quality set with coverage to 22MHz or so.

[radiograham]

I suppose the only advantage of the audiophools getting interested in EF50s would be someone might start making the holders again?

[Argus25]

Originally Posted by radiograham

I suppose the only advantage of the audiophools getting interested in EF50s would be someone might start making the holders again?

Clone sockets are often poor quality.I recently saw some hopeless ones for a Mazda Octal.

The EF50 socket is unique, it has very high tension claws that act over a very small surface area on the valve's pin.

I doubt if the socket cloners could come close to getting the metallurgy right.

Fortunately original ceramic and phenolic sockets are still available for the EF50.

[Radio Wrangler]

I remember having what looked like a PTFE socket for the EF50 back in the sixties.

David

[Argus25]

Have a look at the EF50's in this article on my Argus TV. THe photos don't get the colour balance exactly right, but the EF50's are not quite fire engine red. They have just a faint tint of blue, so the red is fractionally magenta.

I searched to find ones with perfect original paint an the AM logo with the crown. If a valve like the EF50 doesn't inspire the will to build something, probably no valve would:

http://worldphaco.com/uploads/ARGUS.pdf

I have some EF50's that are fire engine red, labelled "Pinnacle" but the paint is slightly orange peel in its texture, and I think they were re-sprayed and re-labelled some time in the late 1950's of 1960's and they are in fact wartime valves.

[turretslug]

Originally Posted by Argus25

Have a look at the EF50's in this article on my Argus TV. THe photos don't get the colour balance exactly right, but the EF50's are not quite fire engine red. They have just a faint tint of blue, so the red is fractionally magenta.

I have some EF50's that are fire engine red, labelled "Pinnacle" but the paint is slightly orange peel in its texture, and I think they were re-sprayed and re-labelled some time in the late 1950's of 1960's and they are in fact wartime valves.

That prompted me to check- yes, the Mullard-branded but also proclaiming "Made in USA" ones are just a little more towards magenta than the Mullard non-USA (supposedly....) ones. Local preference/availability/regulation on paint pigments perhaps.

I gather that Pinnacle were a wholesale re-seller- possibly using the lorry-loads of plain silver VR91s/CV1091s that were swilling around. Maybe the feeling was that folk were more familiar with the Pro-Electron designation than the Services codes.

[G6Tanuki]

Yes, Pinnacle were one of the major rebranders/distributors - in the same vein as Bentley Acoustic Corporation, Haltron, Torvac, Zaerix, Trigon - they bought valves from wherever they could get them and slapped their own brand on them.

Sometimes this meant rebranded Government-surplus stocks, sometimes end-of-production-run stuff or 'not-quite-good-enough-for-the-military' stuff from mainstream manufacturers, sometimes imports from Eastern Europe communist-states desperate to sell anything in return for Western currency.

Personally, I doubt any EF50s were made after WWII ! The demand for them fell away quickly once the likes of the EF91 and EF80 appeared on the TV scene, and there must have been loads of EF50s in Government warehouses. to maintain supply.

[Heatercathodeshort]

The American all metal valves are incredibly reliable. J.

[thermionic]

Originally Posted by Argus25

I searched to find ones with perfect original paint an the AM logo with the crown. If a valve like the EF50 doesn't inspire the will to build something, probably no valve would.......

....I agree... building a TV to utilise my EF50’s is out of my skill set unfortunately, but it’s one reason why I wanted to use it for my little pre amp, and of course they are on display! I have a small stock of various versions of this valve, originally to keep as spares for a few of my vintage Pye TV’s.

Cheers. SimonT.

[llama]

Dad built a ViewMaster as and when the plans came out. He used to extol the virtues of "Sylvanian Red" EF50s but I don't know if he ever got round to using them. My guess is there's no difference between those and their contemporaries but does anyone know? And what company/country/province is "Sylvania"?
Graham