Rebuilding electrostatic CRTs

[timmy]

well yes but the gun should be left outside the spacecraft to be replaced in the bulb after the phosphor is done inside the spacecraft, lol,lol

[N2IXK]

Originally Posted by timmy

well yes but the gun should be left outside the spacecraft to be replaced in the bulb after the phosphor is done inside the spacecraft, lol,lol

One of those spacecraft with an artificial gravity generator, right?

[wa2ise]

NASA has a large vacuum chamber they use to test satellites and space probes. Though I doubt you could borrow it...

[N2IXK]

Sealing the removed gun back onto the neck would be interesting challenge as well. How does one operate a glass lathe in a vacuum?

[timmy]

anything is possible these days, as we should look up to the stars for answers, lol,lol

[NoPegs]

Originally Posted by N2IXK

Sealing the removed gun back onto the neck would be interesting challenge as well. How does one operate a glass lathe in a vacuum?

Lasers!


Well, actually the normal way. The flames engulf the glass, so conduction of heat energy is the prevailing process, you just have to do some modifications to the torches themselves so they are prepared for exhaust into 0.0PSIA instead of ~14.XPSIA. (0PSIG is 14.7PSIA, Gauge and Absolute.)



If one were inclined, I believe it would be feasible to construct an inert atmosphere glove-box type system for handling such tasks down here at the bottom of ye-olde gravity well. Not sure what inert gas would be best to use, something easy to pump down but also easy to get "four-nines" purity economically. I haven't checked the Ar prices recently but they have to be cheaper than Xe. Argon should be easy enough to pump to a solid hard vacuum when all is said and done. Oddly enough, you can weld glass in an oxygen-free environment fairly easy. Go look up atomic hydrogen welding. Think of it as similar in principle to a plasma-cutter head, but works without oxidizer. (And much, much hotter!) Hot enough to weld tungsten... Glass is a walk in the park!

Originally Posted by N2IXK

Sounds like a plan, but settling new phosphor screens might be a bit of a challenge in zero-G.

As for phosphor deposition in free-fall? Centrifuge the jug, suction up the majority of the supernatant solution following successful precipitation/deposition, instead of decanting it off, then freeze the remaining film of watery phosphor in place thermally, and proceed to sublimate off the remaining water via hard vacuum. Then pick up as normal.

[bgadow]

Before I started reading up on the subject (before websites like this one) I used to assume that all picture tubes were rebuilt in big vacuum chambers of some sort.

[NoPegs]

Originally Posted by bgadow

Before I started reading up on the subject (before websites like this one) I used to assume that all picture tubes were rebuilt in big vacuum chambers of some sort.

The closest thing that actually happened that way is of course NuVistor production.

[old_coot88]

(Edit) NoPegs sed it first (nuvistors).

[Dave S]

Originally Posted by bgadow

Before I started reading up on the subject (before websites like this one) I used to assume that all picture tubes were rebuilt in big vacuum chambers of some sort.

I've seen photos of a big, demountable CRT setup they used in developmental work at RCA's Princeton Labs. The front pops open and they could insert whatever guns or screens they were testing and re-pull a vacuum and give it a go. Pretty slick!

[Tom Albrecht]

Originally Posted by N2IXK

Sounds like a plan, but settling new phosphor screens might be a bit of a challenge in zero-G.

That's what a centrifuge is for. So obviously this will be no problem. Start sending tubes...

[wa2ise]

Originally Posted by Dave S

The front pops open and they could insert whatever guns or screens they were testing and re-pull a vacuum and give it a go.

I imagine the cathodes were thrown away once reexposed to air.

Just be careful of the exhaust products of your gas flame in vacuum that they don't get on the cathode.

[timmy]

ok, by now we all should have been trying to track down replacement guns for these litte tubes, there are plenty out there waiting to be rebuilt.

[Telecruiser]

Would the gun from an oscilloscope tube work? Seems like it should. There are still a lot of those lurking about.

[timmy]

yes they are around and the gun is the same however the gun would have to be new as you cannot take a scope gun out of a working scope tube and put it in a b&w tube. the gun hits air its done.....