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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 21st May 2019, 7:10 pm   #1
geeoboeh2s
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Default An interesting thermionic device.

There are only two contacts, a 1mm lead and a normal valve top cap.

There is no longer a vacuum in the glass envelop with the 1mm lead. The other envelop with the top cap has a much finer wire. The two devices meet in a metal housing. The housing is probably steel - it is magnetic.

Could it be a surge arrester or fuse with the housing acting as a heat sink

What is it likely to have been used for?

Chris
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Old 21st May 2019, 7:31 pm   #2
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Default Re: An interesting thermionic device.

I'm probably miles off here, but I thought it could be some kind of spark igniter with the 1mm lead being an electrode and the part below being some kind of current limiting/short circuit protection in case the electrode were to get too close to it's opposite number... As said, likely way off the mark but am also fascinated to learn what it actually is & it's intended use.
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Old 21st May 2019, 7:35 pm   #3
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Default Re: An interesting thermionic device.

I'm wondering about the magnetic metal bit - and pondering if it could be some sort of TR-switch for inserting in a waveguide?

(these were designed to ionise very quickly when subjected to a pulse of microwave energy, so providing a short-circuit - often in conjunction with a 1/4-wave of waveguide - across the receiver input to prevent the receiver being desensitized).


If it is a TR-switch imay not have contained a vacuum; TR-switches often used Helium or sometimes even water-vapour.
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Old 21st May 2019, 9:10 pm   #4
G8HQP Dave
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Default Re: An interesting thermionic device.

The bit below the wire looks rather like it has a glass-encapsulated diode inside it. However, I realise that this type of package was used for other devices too.
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Old 22nd May 2019, 8:52 am   #5
M0FYA Andy
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Default Re: An interesting thermionic device.

I've searched the online valve museums, but failed to find anything looking like this.

Andy
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Old 22nd May 2019, 10:48 am   #6
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Default Re: An interesting thermionic device.

Maybe the steel housing provided a third internal connection?
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Old 22nd May 2019, 11:37 am   #7
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Default Re: An interesting thermionic device.

I've added some more pictures taken from different angles.
It looks as though the 1mm wire terminates in a small block inside the envelope. Again this looks coppery but may be the same material as the housing.
I thought that the hole in the housing may contain an Allen screw but I have a reasonable selection and nothing fits.

Chris
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Old 22nd May 2019, 11:55 am   #8
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Default Re: An interesting thermionic device.

My guess is that it is an X-ray tube.

(There is a very wide range of shapes and styles of these)
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Old 22nd May 2019, 1:07 pm   #9
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Default Re: An interesting thermionic device.

I've seen nothing like this either! However, I doubt that it is thermionic. There aren't enough connections for a heater, and I can't see any any other way of heating a cathode to emitting temperature (eg lens and sun's rays).

There seems to be no getter.

Is there any continuity between the two connections? I'd guess not, but if there is, it could be a vacuum thermistor type of thing.
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Old 22nd May 2019, 1:25 pm   #10
geeoboeh2s
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Default Re: An interesting thermionic device.

If a source gets hot enough it will emit electrons but these will just form a space charge and there will not be a flow of current until a positively charged source is introduced. I perhaps should not have said thermionic without being able to confirm that the wire gets sufficiently hot. However both tubes are evacuated, or at least were.
The tube with the 1mm wire definitely had a getter. Apart from the deposit on the glass due to the loss of vacuum the structure can still be seen inside.

Chris
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Old 22nd May 2019, 1:36 pm   #11
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Default Re: An interesting thermionic device.

I wonder if it's magnetron related?

Lawrence.
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Old 22nd May 2019, 2:09 pm   #12
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Default Re: An interesting thermionic device.

Some sort of possibly incomplete spark gap switch detonator for an atomic bomb?
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Old 22nd May 2019, 5:07 pm   #13
Martin G7MRV
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Default Re: An interesting thermionic device.

Atomic detonators used Krytron cold cathode switch tubes.

But I think the spark gap idea might be the right way to go, some form of triggered spark gap?


Take a look here http://www.ase-museoedelpro.org/Muse...adar_tubes.htm

maybe a klystron or magnetron but incomplete?
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Old 23rd May 2019, 1:12 pm   #14
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Default Re: An interesting thermionic device.

My guess is some sort of microwave T-R switch: it has that 'certain look'.

Al.
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Old 24th May 2019, 9:58 pm   #15
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Default Re: An interesting thermionic device.

I've been having a search through Google for this device, as one does. The closest I can see is here:
http://www.electricstuff.co.uk/sparkgaps.html#krytron
Sylvania 1B26

Malcolm
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Old 24th May 2019, 11:10 pm   #16
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Default Re: An interesting thermionic device.

A quick google shows some of those radar valves contain radioactive cesium or radium to assist the ionisation threshold.
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