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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 27th Aug 2018, 12:49 pm   #1
Nukeybrown
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Default Has anyone seen a valve like this before?

Or knows what it is for? Came with a lot of other stuff.
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Old 27th Aug 2018, 12:52 pm   #2
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Default Re: Has anyone seen a valve like this before

Search "acorn valve"- a classic early (mid '30s) example of the attempt to extend effective performance into the VHF region.
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Old 27th Aug 2018, 1:05 pm   #3
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Default Re: Has anyone seen a valve like this before

So worth anything ? Or bin
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Old 27th Aug 2018, 1:11 pm   #4
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Default Re: Has anyone seen a valve like this before

Acorn valve. Fun to play with and were used quite extensively by amateur radio operators in home-brew VHF equipment. I think they were used in military equipment originally. Not sure what their maximum frequency range is but there is plenty of info available on the internet and probably within these forums.
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Old 27th Aug 2018, 1:48 pm   #5
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Default Re: Has anyone seen a valve like this before

Some reading.
http://www.r-type.org/articles/art-151.htm
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Old 27th Aug 2018, 1:48 pm   #6
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Default Re: Has anyone seen a valve like this before

From what I can remember, the two main types we used were the 955 and 954, getting hold of a suitable base/holder could be a problem.
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Old 27th Aug 2018, 1:54 pm   #7
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Default Re: Has anyone seen a valve like this before

It's most probably a 955

http://www.r-type.org/exhib/aaa0110.htm

A VHF triode somewhat similar to half of a 12AT7/ECC81. It's raison d'etre is the very short connections to the electrodes offering little series inductance.

954 is the pentode of the family and has pins top and bottom in the glass pinches. as well as the ring of pins the 955 has.

Plugging and unplugging these valves was very difficult due to stressing the seals.

The socket looks like a white pottery ring with clips bolted to it for the pins. It converts a tiny valve into something quite space-hungry.

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Old 27th Aug 2018, 2:05 pm   #8
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Default Re: Has anyone seen a valve like this before

They were used in a lot of late-1930s VHF gear - for example the Hallicrafters S27 receiver which was instrumental in identifying WWII German 'Knickebein' radio-navigation beams directed at the UK.

https://en.wikipedia.org/wiki/Battle..._for_the_beams
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Old 27th Aug 2018, 2:13 pm   #9
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Default Re: Has anyone seen a valve like this before

Quote:
Originally Posted by Nukeybrown View Post
So worth anything ? Or bin
Don't bin it even if it is of no interest to you.

Looking on the sold listings in the ebay advanced search suggests you could expect to get about 8 for it.
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Old 27th Aug 2018, 5:33 pm   #10
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Default Re: Has anyone seen a valve like this before?

I think I paid one shilling for mine, but it was a few years ago!
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Old 27th Aug 2018, 6:12 pm   #11
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Default Re: Has anyone seen a valve like this before?

I got one in a box of miscellaneous stuff at one of Jim Fish's clearout sales. I never did find a use for it, and it was complete with its base.

I wonder how many did get used?

The RSGB 2 metre converter in the handbook of the time used the much posher 6CW4 Nuvistor. And I never found one of those...

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Old 27th Aug 2018, 6:22 pm   #12
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Default Re: Has anyone seen a valve like this before?

Type 954,955 etc.
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Old 27th Aug 2018, 8:34 pm   #13
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Default Re: Has anyone seen a valve like this before?

Anyone who has some of these, there are some simple circuits on the internet but all are for shortwave.
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Old 27th Aug 2018, 8:36 pm   #14
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Default Re: Has anyone seen a valve like this before?

Anyone that wants this one let me know
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Old 27th Aug 2018, 9:36 pm   #15
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Default Re: Has anyone seen a valve like this before?

The first valve radio I ever built, back in the early 60s, used a B7G-based DF91 battery valve, but then I rebuilt it using a 954 acorn valve simply because it looked much more interesting! A long time ago now...………..

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Old 28th Aug 2018, 11:20 am   #16
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Default Re: Has anyone seen a valve like this before?

Nukeybrown you have a PM.
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Old 28th Aug 2018, 12:02 pm   #17
M0FYA Andy
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Default Re: Has anyone seen a valve like this before?

Another snippet regarding acorn valves.

As noted above, these were used in a lot of military equipment in the late 30s. But then the UK Air Ministry issued an edict that they were not to be used in any new equipment.
I've never seen a definitive explanation of the reason for this ban, my only guess could be that they weren't manufactured in the UK, and we didn't want to be reliant on valves only available from the US.
We did of course use US-manufactured valves throughout the war, for example EF50s made by Sylvania, but they were also made by Mullard.

Does anyone have any other suggestions for this ban?

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Old 28th Aug 2018, 12:31 pm   #18
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Default Re: Has anyone seen a valve like this before?

By coincidence I have just fully restored a US military grid dip oscillator (GDO) - model AN/PRM-10. The tuning head uses a 955 acorn valve, and during post restoration testing the unit was found to be very close to original spec on all seven ranges from 2MHz to 400MHz. A very capable and useful piece of test equipment, and a good example of the time when acorn valves were used - mainly in the US, where VHF/UHF working was required. Definitely a valve of it's time and worthy of a place in vacuum tube history.
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Old 28th Aug 2018, 2:04 pm   #19
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Default Re: Has anyone seen a valve like this before?

400Mhz was quite an achievement for 1930's technology!
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Old 3rd Oct 2018, 8:42 pm   #20
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Default Re: Has anyone seen a valve like this before?

Are you still in need of a 6CW4 ? Or even an 8056 ? Intend having a clearout (sometime !)
Quite by chance just come across two porcelain Acorn holders complete with 954 and 955 ! Last used by me and a schoolmate in about 1952. Mind you, we were using dry batteries -----so they would have been 958 and 959. Memory is blurred !
Perhaps I should have used "Terminally Confused" as my username.
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