Hello,

can somebody identify this tube?

http://www.viehl-radio.de/homeda/aktuell/aktuell27.jpg
http://www.viehl-radio.de/homeda/aktuell/aktuell26.jpg
http://www.viehl-radio.de/homeda/aktuell/aktuell25.jpg

I have heard that this was taken from a mechanical television set. What kind of lamp or tube is it?

Kind regards,
Eckhard

looks more like a neon bulb , than a tube ....

I believe that is a crater lamp - a neon lamp that produces a small intense spot of light. It can be used in a mechanical TV with a lens wheel or lenses and mirror wheels, or possibly in an early fax machine

I imagine that something like this neon tube might have been used to record sound onto movie film. The response time of the neon bulb would be a lot quicker than a incandescent light bulb, and you avoid having the drive issues involved with driving a variable shutter (like that in a record cutter machine).

It is a crater lamp. They were used in mechanical TV sets and also in fax machines:

http://www.earlytelevision.org/western_empire_restoration.html

Hello together,

thank you very much for your feedback.

Kind regards,
Eckhard

Hello,

does somebody know how I can test the crater lamp? Which voltage and power is necessary for operating?

Kind regards,
Eckhard

The strike voltage (when the lamp first comes on) is probably around 200 volts. Maximum current for full brightness is probably 20-40 ma. The center of the base is most likely positive, though you won't hurt the lamp by reversing the polarity.

Hi Steve,

is there a filament voltage?

- Eckhard

I forgot that. Are there three connections on the tube? The crater lamp I have uses about 2 volts AC on the filament. Use a variable voltage - there will be one point where the glow will be confined mainly to the chamber and the spot.

Hi Steve,

here is a photo of a test:

http://www.viehl-radio.de/homeda/aktuell/aktuell28.jpg

The lamp light up with 170V qith a spot in the middle of the cylinder, and with increasing voltage, the whole cylinder and the connection wires light up. But there is no bright spot as expected. The current is 10 ma.

Is this the result what one might get?

Kind regards,
Eckhard

If you expected to produce a narrow beam of light, that will not happen. However, all the output emits from that small hole and can be focussed by a lens. It is not at all as intense or collimated as a laser.