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Old 1st May 2021, 8:19 pm   #1
G6Tanuki
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Default "Power" Acorn valves.

Sorting-through my big-box-of-valves, I came across a bunch of WWII-and-earlier era 954 /VT-120 Acorns [RCA and Tung-Sol, in their original boxes].

Which got me wondering.

The little Acorns were designed for VHF/UHF receiver duty [mine are earmarked for a rebuild of my Hallicrafters S27] but it led me to wonder - were there ever any 'power' Acorns.

By which I mean triodes/tetrodes with anode-dissipations of something like 5 Watts - for use in WWII-era mobile UHF transmitters/RADAR-countermeasures-stuff in aircraft?

There seems to be a big jump between the little Acorns and the big dual-valves like the 829B and 832A.

Surely there would have been - during WWII - a need for a VHF/UHF valve that could deliver something between 5 and 15 Watts of RF?
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Old 1st May 2021, 11:31 pm   #2
Bazz4CQJ
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Default Re: "Power" Acorn valves.

Google CFT-15-E, sort of Acorn, the glass is about 40mm high and wide.

I'm sure I recall seeing something from WWII that had side-pins and was about QQV03-20 dimensions, in fact, I might have one if I can find it.

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Old 2nd May 2021, 10:52 am   #3
M0FYA Andy
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Default Re: "Power" Acorn valves.

The 1630 is a 'giant acorn', although not a power device.

They do look good!

Andy
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Old 2nd May 2021, 1:06 pm   #4
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Default Re: "Power" Acorn valves.

Getting a 1630 in or out of its 12-pin socket must have been "interesting"!
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Old 2nd May 2021, 4:09 pm   #5
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Default Re: "Power" Acorn valves.

Some fascinating ones there: the 1630, I note, makes use of 'secondary emission' - something which was also tried - generally without success - by quite a few other manufacturers [Philips/Mullard had the EE50 and EFP60 intended for TV use but they never caught on].
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Old 2nd May 2021, 7:37 pm   #6
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Default Re: "Power" Acorn valves.

That 1630 is indeed a step beyond, most intriguing! There must have been quite a few "Tefal men" working busily away in their labs all round the world in that hey-day of pushing the (valve) envelope to new technological frontiers, some would have stalled and faded, others like the cavity magnetron revolutionised the era.

I suppose the entertainingly weird 703A could count as a "power acorn".
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Old 2nd May 2021, 8:57 pm   #7
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Default Re: "Power" Acorn valves.

Was there much development of the acorn type at all during WWII?

With the emphasis on speedy mass production including valves for VHF, the early acorns 954, 955 and 956 were “rebottled” as B7G types in 1941, respectively 9001, 9002 and 9003. Then in the USA at least additional B7G types were developed for VHF applications. The 6C4 triode (1942) had a nominal 3.5 W anode dissipation, and according to RCA, in class C it could dissipate 5 W. Apparently, there were aircraft installations that used multiple 6C4 sets.

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Old 26th Sep 2021, 7:40 pm   #8
Martin_Calva
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Default Re: "Power" Acorn valves.

Quote:
Originally Posted by G6Tanuki View Post
Sorting-through my big-box-of-valves, I came across a bunch of WWII-and-earlier era 954 /VT-120 Acorns [RCA and Tung-Sol, in their original boxes].

Which got me wondering.
(...)

Surely there would have been - during WWII - a need for a VHF/UHF valve that could deliver something between 5 and 15 Watts of RF?
There were such valves and they were known as 'doorknob valves'. 316A for example. http://www.r-type.org/exhib/aai0003.htm
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Old 1st Oct 2021, 3:54 pm   #9
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Default Re: "Power" Acorn valves.

Yes, the bigger power acorns 832 (VT118) were used in the US built VHF transmitters for WW2, for example the ubiquitous TR5043 aka SCR522 (US version of the TR1143) uses them.

The TR5043 had a higher maximum frequency than the TR1143 so it was more used in bombers because fighter command had used up all the lower VHF slots.

The snag with the 832 was that it required external neutralisation to avoid oscillating. The Britsh VHF valves like VT501 had it built in.
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