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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 3rd Oct 2018, 9:11 pm   #21
Rileyman
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Default Re: Has anyone seen a valve like this before?

Wasn't it a 959 1.25v filament perhaps??

Laurie.
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Old 4th Oct 2018, 9:15 pm   #22
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Arrow Re: Has anyone seen a valve like this before?

Home-brew VHF GDO for the 2m. Amateur Radio band. Will also radiate a signal in its freq. range, acting as a VHF sig. gen.: useful for lining up 145 MHz VHF converters.
Haven't used it for years: it's just a piece of memorabilia from yesteryear.

Al.
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Old 4th Oct 2018, 10:33 pm   #23
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Default Re: Has anyone seen a valve like this before?

Quote:
Originally Posted by M0FYA Andy View Post
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?

Andy

Andy,

as I recall the relevant letter said something about supplies of acorn valves being unreliable because so much VHF kit was using them. This was in the days before valves like the EF50 became available I think.

Richard
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Old 5th Oct 2018, 12:03 am   #24
martin.m
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Default Re: Has anyone seen a valve like this before?

Here is an example of an early 1950s signal generator that uses Acorn valves.
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Old 5th Oct 2018, 12:23 am   #25
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Default Re: Has anyone seen a valve like this before?

Being interested in GDO's means that I'm interested in Acorns. Something I just found out a week or so ago is that the 955 was re-packaged as a B7G valve during WWII and designated 9002, with CV and VT derivative numbers too. http://www.r-type.org/exhib/aaa0254.htm. I've never encountered any reference to them previously, but a few of them show up on ebay at no great cost.

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Old 5th Oct 2018, 12:07 pm   #26
G8HQP Dave
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Default Re: Has anyone seen a valve like this before?

I was just about to say that acorn-like valves soon became available on B7G base. Presumably these were more robust, both in use and during replacement.
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Old 6th Oct 2018, 7:35 pm   #27
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Question Re: Has anyone seen a valve like this before?

Quote:
Originally Posted by Bazz4CQJ View Post
Something I just found out a week or so ago is that the 955 was re-packaged as a B7G valve during WWII and designated 9002
Thanks for that - which I never knew. I've got a few 9001 valves in stock: any idea if they are a redo of an Acorn?

Al.
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Old 6th Oct 2018, 7:46 pm   #28
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Default Re: Has anyone seen a valve like this before?

9001/9002/9003 were basically B7G reworks of Acorns, yes. The Acorn had leadout-sealing issues and so by the early-1940s when WWII-requirements for millions of B7G-based valves for things like the BC1000 [WS31] military radios and RADAR stuff emerged in the US it made sense to re-engineer the old Acorn electrode-structures to fit the newer, more-reliable/cheaper-to-produce envelope.

The 6AK5 is my favourite from that era: Small, compact, reliable... what's not to like.

[There was an interesting diversion - the likes of the 717A - http://www.r-type.org/exhib/aab0012.htm and the 387A - https://www.radiomuseum.org/tubes/tube_387a_we.html - which were electrode-assemblies really rather like the Acorns but fitted into old-style Octal bases. Long lead-outs made these really not worth pursuing above about 40MHz]
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Old 6th Oct 2018, 8:48 pm   #29
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Default Re: Has anyone seen a valve like this before?

The pins on the Acorns seem to be quite prone to corrosion; I've seen some real stinkers. In valves in the UK, this might date back as far as crossing the Atlantic deep in the bowels of the Liberty ships! The ones with the worst corrosion have often lost their vacuum (are we back to 'oxide jacking' again?). I think that the cardboard used to pack them seems like it might be prone to holding dampness. Anyone with NOS Acorns, especially in the original boxes, might consider checking them and perhaps wiping some Vaseline on the pins. Even acknowledging their shortcomings, I think they score pretty highly for something made back in the 1930's.

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Old 12th Oct 2018, 1:09 pm   #30
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Default Re: Has anyone seen a valve like this before?

As a young lad, I built my first short-wave receiver around a 955 in a small biscuit tin with an external audio amp. I remember being very impressed by receiving Radio Brazzaville (Africa) with it.
As I recall, the valve holder was more expensive than the valve ! Tony.
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Old 12th Oct 2018, 9:25 pm   #31
Rileyman
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Default Re: Has anyone seen a valve like this before?

Quote:
Originally Posted by Sideband View Post
400Mhz was quite an achievement for 1930's technology!
My 1942 copy of the A.R.R.L. "Radio Amateur's Handbook" contains details of a 750 m/cs oscillator employing a 955 Acorn !!
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