VACUUM TUBE COLLECTING > Tube Discussion

Can you ID this mystery tube/bulb?

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Mónico González:
Could be an electrode section for a green phosphor photocopier's tube?
These tubes often are preheated by filaments and excited by HV only when the image are scanned, being turned off again once the exposure have been done, but maintaining the filaments heated during the off time.
Neon (or mercury vapor) sign cold cathode tubes usually doesn't has any kind of thermionic emitter, because, as everybody knows, the arc strikes by itself in virtue of the high voltage drop between its electrodes that causes the ionization of the gas, being not necessary any kind of "help" to start.
But in copiers, things are quite different, due to the need of use lower voltages than in cold cathode tubes, so the need of certain "priming" prior to apply the voltage accross the tube, as in regular pre-heated fluorescent lamps does occur.
This method allows also a more exactly on-off timing and a higher efficiency in Lm/W because the presence of a coated incandescent filament previously to the arc striking.
But a close looking of it, seems to show a kind of "diode" structure, in wich there is a direct heating cathode (the filament) and the anode cylinder.
It's a curious detail to note that the lead-in wires are driven to the outside of the stem separately and isolated ones from anothers, this allows that both pieces (cylinder electrode and filament) could be connected also separately to different circuits and potentials. What for? (this seems to confirm my "diode theory").
Perhaps could be it a sort of Pirani Gauge for vacuum measuring? or perhaps the electrode for a high current tube (for copiers again) that needs a strong shielding to protect the emitter coating of filaments against sputtering and damage due to intense ionic bombardment?
These are only some ideas.
In any case, they are obviously pre-mounted pieces for ulterior tube assembling

High quality pictures too, Tim!.
Regards.
M. Gonz?lez.

James:
This is indeed the electrode for a neon sign tube.  Most neon artists can bend the glass for their tubes and gas fill them, but cannot make the critical glass-to-metal dumet seals at the tube ends.  Thus the entire component in Tim's photo is a standard mass-produced part which makes the neon artists life easier.

The cork is just there to keep dust out of the assembly during transit.  All the signmaker has to do is remove the cork and then simply seal the open end of this component onto his neon tube.  It saves them a huge amount of work.  One of the principal suppliers is Masonlite, http://www.masonlite.dsl.pipex.com/home.htm  You can buy them off the shelf to suit a variety of different tube diameters and glass types.

Best regards,

James.

jon:
I remember seeng flourescant tubes often had filaments in them. I can't remember why this is, but it has something to do with allowing them to start without High Voltage.  they do look very similar to the electrodes used for neon lights, but I too am surprised to see all the individual wires insulated from each other.

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