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What are the most interesting vacuum tubes in your collection?

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radhoo

Sat Feb 19 2011, 09:51AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Even if they are considered obsolete by some, the vacuum tubes still provide interesting applications, and in some cases are irreplaceable by silicon.
I hope that other members will join and contribute, based on their experience and knowledge.
I suggest we build this thread, to contain the best of our tube collections, like a virtual museum, if you want.
If possible, please try to upload quality photos, that others would enjoy seeing.
Also based on your knowledge it would be great to include a few words on the purpose of the vacuum tube pictured. This way we all get to learn something. So here it goes:

radhoo

Sat Feb 19 2011, 09:54AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Transmitting Triode 710A (200W, 600MHz max)

More details available here:

Proud Mary

Sat Feb 19 2011, 12:20PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

EF97 - low voltage variable-mu pentode

So why this modest looking valve instead of the usual 4HV power porn?

EF97 was designed to be fully functional with an anode voltage of as little as 6.3V, with the screen grid at a tiny 3.2V.

EF97 ran directly from a car battery, and so did away with the need for costly HV batteries, vibrating reed invertors, or dynamotors usually required to supply anode voltage to car radio reciever valves.

Its heyday in car radios and record players was shortlived. Manufacture began in 1958 and had ended by the mid-60s, a period of radical transition in the electronics industry. The Thermionic Age was coming to an end, and the Solid State Age had just begun, so EF97 and its fellow car radio valves were quickly forgotten when germanium transistors began to appear in commercial designs.

But for the experimenter, the car radio valve remains an easy way of getting into thermionic technology without the danger of electric shock, or the need for specially built smoothed HT power supplies.

Some, but not all, of the car radio valves worked in space charge grid mode. In these valves, such as 12K5, g1 is designated as 'space charge grid' and held positive as an electron accelerator, while g2 - normally the screen grid - is designated as 'control grid.' Check the data sheets to avoid mis-wiring.

There are plenty of 'space charge tube' circuits to be found on Google.

1298115081 543 FT0 Ef97 Datasheet Extract

radhoo

Sat Feb 19 2011, 03:51PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

714 7021 Gas and Mercury Thyratron.
A thyratron is a type of gas filled tube used as a high energy electrical switch and controlled rectifier.
I might try one of these in a small SG tesla coil, as a spark gap replacement.

The datasheet, as PDF: ]714_7021.pdf[/file]

Finn Hammer

Sat Feb 19 2011, 09:04PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

300B is an audio power triode, here in a recent version with globe shaped envelope.
Audio lore (or hype if you wish) has it that the globe shaped tubes sounded better, thus there was a market for this variety.

What I find interesting about this valve, is that it has acheived cult status amongst audiophiles, and therefore can be sold at prices that are much higher than that charged for even bigger valves.

That's the way it is amongst audiophiles.

Cheers, Finn Hammer

radhoo

Sun Feb 20 2011, 11:13AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Reflex Klystron 6236, with a frequency range of 3.8 to 7.6 GHz with 125mW output.
Klystrons are used as amplifiers at microwave and radio frequencies to produce both low-power reference signals for superheterodyne radar receivers and to produce high-power carrier waves for communications and the driving force for modern particle accelerators.
This tube was used by the military, judging by the output power it probably functioned in a RF generator.

A circuit using this klystron:

Taken from:

Wish I had more data on it.

Bored Chemist

Sun Feb 20 2011, 01:39PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

I don't collect tubes, but I have a dead 3CX1500D3 I use as a paper weight.

radhoo

Sun Feb 20 2011, 02:33PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Bored Chemist wrote ...

I don't collect tubes, but I have a dead 3CX1500D3 I use as a paper weight.

Would you post a photo?

Wolfram

Mon Feb 21 2011, 12:55PM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

These are about half of them. The biggest tube in the first photo is the same size as the smallest one in the second

Steve Conner

Mon Feb 21 2011, 01:05PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I have lots of other tubes, but this one is most in the "4HV Power Porn" spirit. I would like to build a RF amp with it some day.

Finn, are you still using that beautiful 300B hi-fi amp I saw when I visited you in Denmark?

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