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A non audio tube. I'm totally lost, please help
A non audio tube. I'm totally lost, please help
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Old 30th November 2011, 11:47 AM   #1
vascoadao is offline vascoadao
diyAudio Member
Join Date: Nov 2011
Question A non audio tube. I'm totally lost, please help

Dear forum members.
Please forgive me for jumping in this forum, but considering my question is vacuum tube related I thought you could help me.
I need some info about a vacuum tube with the following label:
SUNVIC Hot wire Vacuum switch
Type 700
Style 280612

The only info I have is this is used in a 60 years old acid Battery Charger timer.

Forgive me any mistakes but English isn't my first language.
Thank you for your help!
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Old 30th November 2011, 12:04 PM   #2
thaumaturge is offline thaumaturge  United States
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Join Date: Aug 2011
Location: Utah
Well, first answer is that it isn't an amplifying tube, but a set of switch contacts inside a vacuum enclosure made to reduce contact arcing. The hot wire will cause a bimetalic element to flip, either making or breaking the contact as a result. Think of it as a relay. At which current it does this is a guess without manufacture info.
Hope this helps

From Nature, july 1948:

"Hot-wire Vacuum Switches

SUNVIC CONTROLS, LTD., 10 Essex Street, Strand, London, W.C.2, manufacturers of vacuum switches, temperature control and associated equipment, have recently issued a 16-page illustrated pamphlet describing their hot-wire vacuum switches. The Sunvic hot-wire vacuum switch is contained within an evacuated glass tube not much larger than an ordinary radio valve, and is a non-arcing electric relay, the operation of which depends on the fact that when an electric current is interrupted by the separation of two surfaces in a vacuum no arc is formed. The movement necessary to close or open the switch is quite small and is provided by the thermal expansion of a special steel wire through which a control current of some 25-60 m.amp. is passed. The switch contacts are tungsten and are normally held apart against a compressed spring, which is released by the expansion of the hot wire. The operating characteristics of many different forms of hot-wire vacuum switches with various time delays, closing currents and current-carrying capacities are listed, and twelve different standard circuit and wiring diagrams are shown. The hot-wire vacuum switch is capable, in various sizes, of handling up to 10 kW. at 440 volts, and is suitable for controlling alternating or direct currents up to 30 amp. and voltages from 10 to 600."
Noli timere problematum affigit

Last edited by thaumaturge; 30th November 2011 at 12:11 PM.
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