Cx1140 - UK Vintage Radio Repair and Restoration Discussion Forum

sparkymike · 25th Feb 2018, 12:21 pm

Hi, A friend has just bought a CX 1140 thyratron with some other valves at a car boot for a few pounds.
What can this be used for ? Any value ?
Mike.

G6Tanuki · 25th Feb 2018, 12:28 pm

Looking at the spec:

https://www.radiomuseum.org/tubes/tube_cx1140.html

unless you're intending to repurpose a microwave-oven Magnetron as part of your recreation of a WWII-era "H2S" Radar or something, it's probably best mounted on a polished-Mahogany plinth and kept on a shelf in your office as an ornament/talking-point.

[Smaller Thyratrons can be used to build fun projects - I recall seeing a Stylophone-style instrument that used a 6K25 Thyratron as the oscillator]

Malcolm G6ANZ · 25th Feb 2018, 2:32 pm

They are still in use as 'switches' in pulse magnetron line modulators. Simply put they short out a bank of large high voltage caps through a pulse transformer. This then gives a 4uS pulse at 40Kv to fire the magnetron. The magnetron produces megawatts of pulse power. I play with them daily in Clinical linear accelerators.
Malcolm

sparkymike · 25th Feb 2018, 6:55 pm

I now have the other "valves" here and photo enclosed.
Anyone know what their use is ? They all have a flat glass end, opposite to the pins that look to be in different colours. Are they a form of Nixie tube ?
The large fat short one has CV 2316 marked on it, and type TG 2543, on makers label.Maker 20 century Electronics.
The others are all English Electric.
Mike.

TonyDuell · 25th Feb 2018, 6:59 pm

My first guess is that the thinner ones are vidicons (TV camera tubes) and the fatter one is a photomultiplier.

Malcolm G6ANZ · 25th Feb 2018, 8:00 pm

I agree with Mike. The short fat one is photomultiplier and the rest are 2/3 inch vidicons apart from the one on the left which might be a 1 inch vidicon. Part numbers will narrow down the choices.

sparkymike · 25th Feb 2018, 9:13 pm

There are internal,behind the glass part numbers or serial numbers on the thin ones.AK6205/F7618/C4564/B6325.
Mike.

Radio1950 · 25th Feb 2018, 11:20 pm

We used these CX1140 tubes in CSF ER410 civilian airport search radars on L band.
There were two radar transmitters 50 MHz apart diplexed into one antenna.
Each transmitter had an output power of 2.2 Megawatts and a pulse width of 2.5 uS with a PRF of 400 pulses per second to give a nominal useful range of 160 NM.
As Malcolm said, these CX1140 tubes were used to switch dump the energy in a delay line across the cathode of a water cooled magnetron, with anode earthed.

Our thyratrons were switching 25 KV at about 120 Amps.

Thyratrons were utilised because of their low ON resistance and very short switching times, and can be "primed" before switch on with a pre-trigger, to sharpen up the turn on of the thyratron, and hence the magnetron, and to reduce pulse jitter.
They were filled with Hydrogen as the plasma has low resistance and predictable switch times.
Our tubes were relatively long lived eg 20, 000 hrs, and gave off an eerie pink purple glow.
We found EEV brand best.

They look impressive.

Mike

sparkymike · 26th Feb 2018, 9:09 am

They possibly all came from the Marconi factory which was also in our area.
(Essex) .
I have no use for them at all so no doubt will be putting them on a well known auction site. No means of testing them either, so they will have to go as seen.
They mostly look in very good condition apart from the short fat one which has discoloured pins.(15 of them !!) That also had a large valve base with 13 resistors strapped across the pins.
Mike.

sparkymike · 3rd Mar 2018, 6:18 pm

In The above thumbnail, the Vidicon ? with the black plastic cover on the end has the numbers 1704/27 on this cover. I do not know if this bears any clue to the maker of this tube as there are no more idents. on it.
This cover does not seem to want to come off, but might be just a tight fit and nothing to do with the tube, but just put on to protect the lens.
Any comments gratefully received.
Mike.

25th Feb 2018, 12:21 pm	#1
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Cx1140 Hi, A friend has just bought a CX 1140 thyratron with some other valves at a car boot for a few pounds. What can this be used for ? Any value ? Mike.

25th Feb 2018, 12:28 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: Cx 1140 Looking at the spec: https://www.radiomuseum.org/tubes/tube_cx1140.html unless you're intending to repurpose a microwave-oven Magnetron as part of your recreation of a WWII-era "H2S" Radar or something, it's probably best mounted on a polished-Mahogany plinth and kept on a shelf in your office as an ornament/talking-point. [Smaller Thyratrons can be used to build fun projects - I recall seeing a Stylophone-style instrument that used a 6K25 Thyratron as the oscillator]

25th Feb 2018, 2:32 pm	#3
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,042	Re: Cx1140 They are still in use as 'switches' in pulse magnetron line modulators. Simply put they short out a bank of large high voltage caps through a pulse transformer. This then gives a 4uS pulse at 40Kv to fire the magnetron. The magnetron produces megawatts of pulse power. I play with them daily in Clinical linear accelerators. Malcolm

25th Feb 2018, 6:55 pm	#4
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Cx1140 I now have the other "valves" here and photo enclosed. Anyone know what their use is ? They all have a flat glass end, opposite to the pins that look to be in different colours. Are they a form of Nixie tube ? The large fat short one has CV 2316 marked on it, and type TG 2543, on makers label.Maker 20 century Electronics. The others are all English Electric. Mike. Attached Thumbnails

25th Feb 2018, 6:59 pm	#5
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,224	Re: Cx1140 My first guess is that the thinner ones are vidicons (TV camera tubes) and the fatter one is a photomultiplier.

25th Feb 2018, 8:00 pm	#6
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,042	Re: Cx1140 I agree with Mike. The short fat one is photomultiplier and the rest are 2/3 inch vidicons apart from the one on the left which might be a 1 inch vidicon. Part numbers will narrow down the choices.

25th Feb 2018, 9:13 pm	#7
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Cx1140 There are internal,behind the glass part numbers or serial numbers on the thin ones.AK6205/F7618/C4564/B6325. Mike.

25th Feb 2018, 11:20 pm	#8
Radio1950 Hexode Join Date: Apr 2017 Location: Buderim, Queensland, Australia. Posts: 428	Re: Cx1140 We used these CX1140 tubes in CSF ER410 civilian airport search radars on L band. There were two radar transmitters 50 MHz apart diplexed into one antenna. Each transmitter had an output power of 2.2 Megawatts and a pulse width of 2.5 uS with a PRF of 400 pulses per second to give a nominal useful range of 160 NM. As Malcolm said, these CX1140 tubes were used to switch dump the energy in a delay line across the cathode of a water cooled magnetron, with anode earthed. Our thyratrons were switching 25 KV at about 120 Amps. Thyratrons were utilised because of their low ON resistance and very short switching times, and can be "primed" before switch on with a pre-trigger, to sharpen up the turn on of the thyratron, and hence the magnetron, and to reduce pulse jitter. They were filled with Hydrogen as the plasma has low resistance and predictable switch times. Our tubes were relatively long lived eg 20, 000 hrs, and gave off an eerie pink purple glow. We found EEV brand best. They look impressive. Mike

26th Feb 2018, 9:09 am	#9
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Cx1140 They possibly all came from the Marconi factory which was also in our area. (Essex) . I have no use for them at all so no doubt will be putting them on a well known auction site. No means of testing them either, so they will have to go as seen. They mostly look in very good condition apart from the short fat one which has discoloured pins.(15 of them !!) That also had a large valve base with 13 resistors strapped across the pins. Mike.

3rd Mar 2018, 6:18 pm	#10
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Cx1140 In The above thumbnail, the Vidicon ? with the black plastic cover on the end has the numbers 1704/27 on this cover. I do not know if this bears any clue to the maker of this tube as there are no more idents. on it. This cover does not seem to want to come off, but might be just a tight fit and nothing to do with the tube, but just put on to protect the lens. Any comments gratefully received. Mike.