BulbCollector Forums
VACUUM TUBE COLLECTING => Tube Discussion => Topic started by: Tim Hynde on January 04, 2003, 02:06:00 am
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I'd like to try and make a glow lamp but rather than in a bulb sandwiched between glass sheets 1/4" apart about 6"x6". The test would use double sided copper PC board. I realize there are impuritys but it's only a test. Some of these questions may be completly off base so work with me (http://www.bulbcollector.com/ubb/smile.gif)
Q. Do I need to evacuate the glass enclosure or can I just flood it with neon? blow it in one end and lightly vaccume from the other?
Q. If I were to use metal for the 'artwork' inside (instead of my doublesided copper PC board) does it have to be treated or heated in someway to remove impuritys? What happens if this is not done?
Q. Has anyone tried making something similar to the Aerolux or Birdseye models?
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quote:
Originally posted by Tim Hynde:
I'd like to try and make a glow lamp but rather than in a bulb sandwiched between glass sheets 1/4" apart about 6"x6". The test would use double sided copper PC board. I realize there are impuritys but it's only a test. Some of these questions may be completly off base so work with me (http://www.bulbcollector.com/ubb/smile.gif)
I'm no expert, but here's what I know:
Q. Do I need to evacuate the glass enclosure
Yes.
or can I just flood it with neon?
No.
blow it in one end and lightly vaccume from the other?
No. The pressure used in glow lamps is very low (compared to atmospheric pressure which is 760 Torr), somewhere in the range of 8-50 Torr. You need special equipment to reach this low pressure, although something as common as an air-conditioning servicing vacuum pump may be adequate to the task, for hobby purposes.
Q. If I were to use metal for the 'artwork' inside (instead of my doublesided copper PC board) does it have to be treated or heated in someway to remove impuritys?
Yes. This process is called "bake-out" or "bombarding", and involves heating the metal inside the glass envelope to red hot while under vacuum. This is usually done with radio frequency (RF) induction heating equipment, though it reportedly may be possible to do it in some cases (such as with the fine wire elctrodes of a nixie-style tube) by passing current through the device.
What happens if this is not done?
Your glow lamp may not work at all, or work very poorly. The impurities will probably even work themselves out of the metal while the lamp is just sitting there, so it might light right after you make it but not a short time later. Also, your idea to use copper-clad PC board is no good. The adhesive and epoxy resin used in making the board will be impossible to bake out or otherwise render inert.
Q. Has anyone tried making something similar to the Aerolux or Birdseye models?
Yes! There are similar bulbs of recent manufacture being sold on eBay and through outlets such as Spencer Gifts.
Here's a seller listing with several such bulbs currently and recently offered: http://cgi6.ebay.com/ws/eBayISAPI.dll?ViewListedItems&userid=prrob&sort=3&pa ge=1&rows=200&since=30 (http://cgi6.ebay.com/ws/eBayISAPI.dll?ViewListedItems&userid=prrob&sort=3&page=1&rows=200&since=30)
(no relationship to me!)
I don't know whether anyone has succeeded in a hobby/garage project type of setting but it wouldn't surprise me if someone had.
P.S. there are lots of other details of the process that make a big difference to the quality of the end product, such as gas mixture and electrode materials. You really should read a book or few on neon sign making and related subjects before jumping into this.
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Alan "A.J." Franzman
Email: a.j.franzman at verizon dot net
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[This message has been edited by Alan Franzman (edited January 04, 2003).]
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tim,
try checking out "instruments of amplification" by pete friedrichs (available at ). I just got it about a month ago. It is a good source on how to hack a vacuum tube by hook or by crook. he even goes so far as to make a diode from a mason jar, and a triode from some other radom parts. resealability is the key for him as the primitive filaments he produces are apt to burn up in three minutes. the methods are sometimes half baked, but good for an experimenter
I too am interested in making some tubes
(glow tubes and thermionic devices).
regards,
jon