Illuminating a Thyratron (mercury gas discharge)

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SUMMARY

The discussion centers on the construction of a novelty lamp using a thyratron tube, specifically focusing on illuminating mercury vapor. The filament requires 2.5VDC at 7 amps, and the user plans to apply rectified DC from the AC mains to achieve optimal illumination between 0.01 and 0.5 amps. A load resistor configuration includes a 10K rheostat in series with a 2.4k Ohm resistor to manage current flow. Participants share insights on current limiting, voltage considerations, and potential applications of the thyratron, including its use as a regulator tube.

PREREQUISITES
  • Understanding of thyratron operation and characteristics
  • Basic knowledge of electrical circuits and Ohm's Law
  • Experience with DC rectification and smoothing techniques
  • Familiarity with resistor configurations and rheostats
NEXT STEPS
  • Research thyratron tube specifications and applications
  • Learn about DC rectification methods and smoothing circuits
  • Investigate current limiting techniques for gas discharge tubes
  • Explore the use of thyratrons in oscillator circuits
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Electronics hobbyists, circuit designers, and anyone interested in vintage tube technology and gas discharge applications.

bwinter
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I found a thyratron tube at a yard sale recently and I want to build a circuit to heat the filament and illuminate the mercury vapor for purposes of building a novelty lamp.

The filament is just 2.5VDC at 7 amps and I have a transformer for that.

To light the vapor I will apply DC rectified and smoothed from the AC mains.

The illumination is related to current, and to achieve maximum illumination of the electrode I want to achieve something on the order of milliamps, above the current for Townsend discharge but below that of arc discharge. I don't know what those values will be so let's say, between .01 and .5 amps.

So V = IR
120 = 0.01R
12000 Ohm = R1

120 = .5R
2400 Ohm = R2

So my load resistor in series with the thyratron will be a 10K rheostat in series with a 2.4k Ohm resistor.

Hoping for any input from someone with tube experience, if this might work.
 
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I'll be interested to see if you can hold off the avalanche after initiating the glow. I've only used 2D21 , fifty years ago.

Try severely limiting anode current , ie higher anode resistor ?

Keep us posted ?
 
Good to know. Do you think 120V DC rectified is enough? What would be the benefit if any of transforming to a higher voltage?
 
I don't see why you'd nee more voltage.

Cleaner copy of datasheet here

http://www.datasheetarchive.com/dl/7a2e304da0ac6860531847f5de30f97df76ae6/O/3C23
 
Maybe you could use it like a regulator tube in a power supply like the one I built. Also I've uploaded the GE Glow Tube application sheet.

tubesupply A+B.jpg
GE_Glow_Tubes_ETI-176.pdf
 

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dlgoff said:
Also I've uploaded the GE Glow Tube application sheet.

What a great find !

That thing just might stay lit at low enough current.

If not, perhaps make it into a relaxation oscillator at a few hundred hz, fast enough to appear continuous.
upload_2017-1-17_22-11-40.png


We used to do that ^^^^ with NE2's and a 90 volt B battery. I found that some resistance in series with the lamp prolonged its life.
 
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I did it!
HLm9cVl.jpg

Funny operation though. Sometimes it will stay on without the heating filament and sometimes not, even if the current is the same. I have it connected through 168VDC and a series resistor (~2k).
 
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