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Old 9th Jan 2021, 11:35 am   #21
jimscoper
Triode
 
Join Date: Jun 2020
Location: Yalding, Maidstone, Kent, UK.
Posts: 35
Default Re: Valve F3A3 - what are they?

Thanks for all the comments. I don't reckon these are electrometer valves - insulation too poor. Thanks VT for the offer but I have enough to do. On reading up on shell fuses the XFG1 type was used to trigger the loud bang. It's use in model control in the 50s and 60s misled me into thinking it had an RF role.

I have played with the old hearing aid valves, they were much bigger than these F3A3 types. My money is on some kind of shell fuse design that got overtaken by transistors.
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Old 21st Jan 2021, 8:31 am   #22
jimscoper
Triode
 
Join Date: Jun 2020
Location: Yalding, Maidstone, Kent, UK.
Posts: 35
Default Re: Valve F3A3 - what are they?

An update on F3A3

The F3A3 valves were sold (for not much) to a member of MRATHS in Malvern. They have archive material dating back to just post-WW2 but cannot access it during Covid. Better information may follow.

So far it appears F3A3 was a UK development of some metal valves captured at Telefunken's labs post WW2. These were later further developed by the UK's SERL. In late ww2 TFK provided metal valves for the German AA rounds but they were some 25mm long x 8mm wide and it is possible UK development went in that direction post ww2.

SERL undertook research into many secret projects, one of which was from 1945-50 in their very capable valve section into miniature valves for ordnance such as shells and mortar rounds. There was pressure post ww2 to enable 40mm BOFORS rounds to be fitted with prox fuzes for AA service.

The ww2 3" & 5" shell circuits were wax potted. Peeled apart they yielded 4 submini glass valves. Later development led to polythene potting.

The buyer is a bit mystified as to how these valve samples made it 'into the wild'. They were supposed to be secret and under lock and key. They may have been passed to GEC and therefore GEC/Marconi as samples and when transistors came along this development was shelved. A missing piece of the puzzle is what was used before transistors and ICs became proven enough for mortar rounds. Were F3A3 devices a production product? If so why have none made it 'into the wild'.
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