What is this valve-like object? - UK Vintage Radio Repair and Restoration Discussion Forum

GMB · 16th May 2005, 5:19 pm

Can anyone identify this valve-like object? It has an air-ministry part number of 10FB/977 and has a B4 base.

It perhaps looks like a thermal relay. It is evacuated. I have shown it in three orientations so you can see it better. One side has fine wires wound up and down round ceramic spacers. There is a spring right at the top.

It measures 160 ohms across what would normally be the heater pins.

GJR 11L · 16th May 2005, 5:38 pm

Here's a link to a site where the device gets a mention, perhaps the person running this valve-related site could advise further?

http://www.rabeng.co.uk/radio/valves.htm

Unless of course the owner of the site is also reading this and doesn't know either!

Gordon · 16th May 2005, 5:41 pm

Possibly a time-delay relay to delay the ht from being applied - operated by a bi-metal strip. That's only a guess!

Gordon.

ppppenguin · 16th May 2005, 8:43 pm

I can well believe Gordon. A heating element plus what could easily be a bi-metal strip.

jim_beacon · 16th May 2005, 10:18 pm

I have a couple of high sensitivity relays with similar internal construstion (I believe they are from furnace control systems). They have a heating element which trips a contact when it passes a certain current, one of mine is marked as 36.45mA, giving some idea of the sensitivity.

Jim.

GMB · 17th May 2005, 9:57 am

I am fairly sure that it doesn't contain a bi-metal strip. The metal strips are solid. What you might not be able to see is that both sides of the strip nearest to the wires and the outer side of the other strip are covered by mica sheets. Any contacts that it may have are open-circuit in the ground state.

Darren-UK · 17th May 2005, 11:24 am

10FB was the reference code given to the starting switchgear for radar equipment by the MoD, or Air Ministry as it was called at the time. If this explains this device, presumably the 977 was the component code.

Gordon · 17th May 2005, 7:24 pm

If you have a lab power supply, any chance of putting a voltage across the 'heater' to see what happens? I would try 6V to start with.

Gordon.

GMB · 18th May 2005, 5:01 pm

I have applied to up 20V with no visible effect at all.

GMB · 12th Aug 2005, 9:31 am

UPDATE
I applied a lot more power to it and as the wires began to glow I noticed that they were collapsing. So I let it cool down and banged in a few times. It was jammed, and now it works: it takes only about 4.5V (no visible glow) to close the contacts, i.e. about 30mA and there is almost no visible movement doing this.
The on-time gets faster with applied voltage and is quite quick (<1sec) but the time to switch off is much longer, several seconds.

Obviously not reliable unless 4 Merlin engines are attached to the chassis nearby.

newlite4 · 15th Aug 2005, 10:45 am

This is a "Sun-Vic" vacuum switch. It is a thermostatic element with an accellerator heater within a vacuum to preserve the contacts. They were patented in the 1930s and were used mainly for heating systems.
Neil

GMB · 15th Aug 2005, 11:34 am

Thanks for that clue Neil. The heater isn't quite an accelerator as it is the only thermal input to the device, i.e. it isn't a thermostatic device itself (being entirely evacuated) but is indeed a vacuum relay of a type used in conjunction with thermstats. Your clue led me to this link: http://www.redremote.co.uk/electricstuff/glassbits.html about half way down this page you will find "Sunco 'Sun-Vic' Vacuum switch contactors" and there is a different device obviously made by the same manufacturer.
So now the remaining question is what this particular device was used for, given its Air Ministry part number, and the fact that it came from a government physics laboratory?

Ed_Dinning · 15th Aug 2005, 12:18 pm

Hi Gents, I've seen them used as starters for discharge lamps, usually the type that gave a very pure spectrum for optical experiments. Sometimes used for mercury vapour rectifiers in professional test equipment.

Ed

16th May 2005, 5:19 pm	#1
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,094	What is this valve-like object? Can anyone identify this valve-like object? It has an air-ministry part number of 10FB/977 and has a B4 base. It perhaps looks like a thermal relay. It is evacuated. I have shown it in three orientations so you can see it better. One side has fine wires wound up and down round ceramic spacers. There is a spring right at the top. It measures 160 ohms across what would normally be the heater pins. Attached Thumbnails

16th May 2005, 5:38 pm	#2
GJR 11L Heptode Join Date: May 2004 Location: Ellington, Northumberland, UK. Posts: 815	Re: What is this valve-like object? Here's a link to a site where the device gets a mention, perhaps the person running this valve-related site could advise further? http://www.rabeng.co.uk/radio/valves.htm Unless of course the owner of the site is also reading this and doesn't know either! __________________ John.

16th May 2005, 5:41 pm	#3
Gordon Pentode Join Date: Oct 2003 Location: Bournemouth, Dorset, UK. Posts: 131	Re: What is this valve-like object? Possibly a time-delay relay to delay the ht from being applied - operated by a bi-metal strip. That's only a guess! Gordon.

16th May 2005, 8:43 pm	#4
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: What is this valve-like object? I can well believe Gordon. A heating element plus what could easily be a bi-metal strip.

16th May 2005, 10:18 pm	#5
jim_beacon Retired Dormant Member Join Date: Mar 2003 Location: Bishop's Waltham, Hants, UK. Posts: 939	Re: What is this valve-like object? I have a couple of high sensitivity relays with similar internal construstion (I believe they are from furnace control systems). They have a heating element which trips a contact when it passes a certain current, one of mine is marked as 36.45mA, giving some idea of the sensitivity. Jim.

17th May 2005, 9:57 am	#6
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,094	Re: What is this valve-like object? I am fairly sure that it doesn't contain a bi-metal strip. The metal strips are solid. What you might not be able to see is that both sides of the strip nearest to the wires and the outer side of the other strip are covered by mica sheets. Any contacts that it may have are open-circuit in the ground state.

17th May 2005, 11:24 am	#7
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	Re: What is this valve-like object? 10FB was the reference code given to the starting switchgear for radar equipment by the MoD, or Air Ministry as it was called at the time. If this explains this device, presumably the 977 was the component code.

17th May 2005, 7:24 pm	#8
Gordon Pentode Join Date: Oct 2003 Location: Bournemouth, Dorset, UK. Posts: 131	Re: What is this valve-like object? If you have a lab power supply, any chance of putting a voltage across the 'heater' to see what happens? I would try 6V to start with. Gordon.

18th May 2005, 5:01 pm	#9
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,094	Re: What is this valve-like object? I have applied to up 20V with no visible effect at all.

12th Aug 2005, 9:31 am	#10
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,094	Re: What is this valve-like object? UPDATE I applied a lot more power to it and as the wires began to glow I noticed that they were collapsing. So I let it cool down and banged in a few times. It was jammed, and now it works: it takes only about 4.5V (no visible glow) to close the contacts, i.e. about 30mA and there is almost no visible movement doing this. The on-time gets faster with applied voltage and is quite quick (<1sec) but the time to switch off is much longer, several seconds. Obviously not reliable unless 4 Merlin engines are attached to the chassis nearby.

15th Aug 2005, 10:45 am	#11
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,805	Re: What is this valve-like object? This is a "Sun-Vic" vacuum switch. It is a thermostatic element with an accellerator heater within a vacuum to preserve the contacts. They were patented in the 1930s and were used mainly for heating systems. Neil

15th Aug 2005, 11:34 am	#12
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,094	Re: What is this valve-like object? Thanks for that clue Neil. The heater isn't quite an accelerator as it is the only thermal input to the device, i.e. it isn't a thermostatic device itself (being entirely evacuated) but is indeed a vacuum relay of a type used in conjunction with thermstats. Your clue led me to this link: http://www.redremote.co.uk/electricstuff/glassbits.html about half way down this page you will find "Sunco 'Sun-Vic' Vacuum switch contactors" and there is a different device obviously made by the same manufacturer. So now the remaining question is what this particular device was used for, given its Air Ministry part number, and the fact that it came from a government physics laboratory?

15th Aug 2005, 12:18 pm	#13
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: What is this valve-like object? Hi Gents, I've seen them used as starters for discharge lamps, usually the type that gave a very pure spectrum for optical experiments. Sometimes used for mercury vapour rectifiers in professional test equipment. Ed