Rickresource Rickenbacker Forum

Makes it look easy, doesn't he?! http://blog.makezine.com/archive/2008/0 ... _tube.html

Yup, amazing. I'd seen that before, and it might even have been posted here. Something to do with your spare time - make tubes!

Sure thing! It's a snap. Why I'll just run right out and get the lathe, and all the other machinery I need tomorrow morning.

JimK

Interesting, but don't those tubes glow a bit too much (due to the presence of gases present because of insufficient vacuum appliedd during manufacture)?

It's simply amazing what can be done with a bit of knowledge, planning and a few tools and equipment.

doctorwho wrote:Interesting, but don't those tubes glow a bit too much (due to the presence of gases present because of insufficient vacuum appliedd during manufacture)?

But is it not true that the best tube manufacturers cannot get that final bit of vacuum due solely to pumping the gas out of the tube to a near-vacuum, and so after manufacture they burn out a "getter charge" with the first applied voltage? The getter charge is a bit of gas-absorbing material placed in the tube at initial manufacture and before closing the glass envelope, sorta like a charge of explosive , that "burns away" the slight remaining oxygen in a tube, and produces that slight bloom of material on the inside of the tube near the base?

doctorwho wrote:Interesting, but don't those tubes glow a bit too much (due to the presence of gases present because of insufficient vacuum appliedd during manufacture)?

The glow could be exaggerated by the video camera. Bright things in video often appear differently than we sense them in reality.

ryan.jones wrote:

doctorwho wrote:Interesting, but don't those tubes glow a bit too much (due to the presence of gases present because of insufficient vacuum appliedd during manufacture)?

But is it not true that the best tube manufacturers cannot get that final bit of vacuum due solely to pumping the gas out of the tube to a near-vacuum, and so after manufacture they burn out a "getter charge" with the first applied voltage? The getter charge is a bit of gas-absorbing material placed in the tube at initial manufacture and before closing the glass envelope, sorta like a charge of explosive , that "burns away" the slight remaining oxygen in a tube, and produces that slight bloom of material on the inside of the tube near the base?

Yes, it's true. It's almost impossible to achieve a complete vacuum, even outer space has stuff floating around in it. Vacuum tubes work best with a total vacuum, so a few molecules of gas left over cause problems. Since you can't get them out with a vacuum pump, the best way to deal with them is to bind them up or absorb them, this is what the "getter" does. It is a combination of highly reactive metals such as barium, calcium, strontium, etc. that is flash evaporated onto the glass envelope of the tube (it's the silvery looking stuff on the tube, often on the top, sometimes on the side). This metal mixture reacts with and absorbs the few molecules remaining in the tube, effectively removing them.

A lotta work involved with that.