Vacuum tube identification - Page 1
Forum section: electronics / beginners

author: (*steve*)
author_rank: Regular Contributor
timestamp: October 08, 2024, 08:27:21 am
content: Hi, I was just given a box full of old vacuum tubes and while I can identify most of them, There were a couple in a package I have never before encountered.There are no part numbers on them and no markings other than the text "Licensed only to extent indicates on carton" that is in raised text on the bakelite octal base. These seem to have two (or three) coaxial connections separated by parts of the glass envelope.I have tried googling using all sorts of descriptions of these tubes, but I have found nothing similar.I don't expect to get an exact identification, but any information about tubes with the same packaging would be useful.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 08, 2024, 08:32:32 am
content: Looks a lot like this:https://tubes-store.com/product_info.php?products_id=804

author: Gyro
author_rank: Super Contributor
timestamp: October 08, 2024, 09:00:54 am
content: They are commonly known as 'Lighthouse valves/tubes' due to their shape. If you do an image search you should see several. Yes it is almost certainly a UHF triode.Possibilities are 2C42, 2C43, 2C46 etc.

author: (*steve*)
author_rank: Regular Contributor
timestamp: October 08, 2024, 11:27:45 am
content: Thanks. You have opened my eyes to another interesting part of electronics history.

author: Gyro
author_rank: Super Contributor
timestamp: October 08, 2024, 12:09:32 pm
content: Nice video find.

author: CaptDon
author_rank: Super Contributor
timestamp: October 08, 2024, 12:49:37 pm
content: They were fitted into cavity oscillators, mixers and amplifiers. Originally used in some of the radars operating just over 1GHz. Ham radio operators used them for the 1296MHz band and some of the old QST magazines and ARRL handbooks included operating data and construction articles. Because of the large seal areas and small vacuum space most of these have gotten a bit gassy over their 80 year life. One of the really nice WWII radar triodes was the VT-127 from Eimac available surplus dirt cheap. Most of them are now display only due to gas. Most have uranium glass and look nice under blacklight!

author: chris_leyson
author_rank: Super Contributor
timestamp: October 08, 2024, 02:05:39 pm
content: The WW2 proximity fuze used miniature triodes and a thyratron to discharge a 1uF cap into the squib or detonator. See "The Deadly Fuze" by Ralph P. Baldwin for details. I've got a disarmed mk 45 fuze from WW2 or the Korean war. It still works but but I've only powered it up from 70V or so and set the heater voltage to 1.2V or maybe 2.4V as some heaters were wired in series. It didn't come with a battery so I had to guess the HT voltage. I think it was developed at John Hopkins university and they have all of the design documents.To make the thing work under several hundred G when fired from a gun there was what resembled a tiny mouse trap above the heater filament to keep the heater under tension and stop it shorting to the cathode. The proximity detector was a VHF oscillator, 120 MHz or so, mounted at the tip and it either used the Doppler effect or loading effects due to capacitive proximity to the ground. I've been meaning to measure the tube characteristics but haven't got around to building a "tube tester" yet. I also need to repair my HP 54610B scope as the power supply died.CheersChris